Guidelines for Undertaking On-Farm Taro Breeding Trials in the South Pacific

Transcription

1 AusAID/SPC TARO GENETIC RESOURCES: CONSERVATION AND UTILISATION Guidelines for Undertaking On-Farm Taro Breeding Trials in the South Pacific Prepared by Davinder Singh, Danny Hunter, Tolo Iosefa and Tom Okpul October 2001

2 2 Copyright Secretariat of the Pacific Community, 2001 The Secretariat of the Pacific Community authorise the reproduction of this material, whole or in part, in any form, provided appropriate acknowledgment is given Original text: English Secretariat of the Pacific Community Cataloguing-in-publication data AusAID/SPC taro genetic resources: conservation and utilisation. 1. Taro-Genetics-Oceania-Congress. 2. Plant conservation-oceania-congresses I. Title II. Secretariat of the Pacific Community AACR2 ISBN Funded by the Australian Government Prepared for publication at the Secretariat of the Pacific Community, Suva, Fiji and at SPC Headquarters, Noumea, New Caledonia. Printed at SPC Suva 2001

3 3 TABLE OF CONTENTS LIST OF ACRONYMS INTRODUCTION BACKGROUND GUIDELINES FOR THE EVALUATION OF TARO IN CONVENTIONAL BREEDING PROGRAMMES Introduction Progeny Evaluation Preliminary Trials Intermediate Trials Advanced Trials Genotype X Environment (G x E) Trials Confirmation Trials and Variety Release GUIDELINES FOR THE EVALUATION OF TARO IN PARTICIPATORY PLANT BREEDING PROGRAMMES Introduction Taro Improvement Project (TIP) Varietal selection Clone selection Participatory plant breeding Breeding Clubs Annexes ANNEX 1: DATA SHEET FOR ASSESSING VARIOUS PLANT AND CORM CHARACTERISTICS IN GXE TRIALS FOR TECHNICAL EVALUATIONS ANNEX 2. ISSUES THAT NEED TO BE DISCUSSED BEFORE PLANNING A PROGRAMME OF PARTICIPATORY PLANT BREEDING ANNEX 3: TIP EVALUATION PROGRAMME ANNEX 4: TIP INFORMATION FORM ANNEX 5: TIP FIELD EVALUATION...37 ANNEX 6: TARO EATING QUALITY RATINGS...38

4 4 LIST OF ACRONYMS BARC CIAL CGIAR DI EHL G x E HR ICA IPGRI MAFFM NARI NGO PPB PIC PNG PVS RCBD SAVE SPC TIP TLB USP VR Bubia Agricultural Research Centre Local Agricultural Research Committee Consultative Group for International Agricultural Research Disease intensity Effective healthy leaf number Genotype by environment interactions Horizontal resistance Colombian Agriculture Research Institute International Plant Genetic Resources Institute Ministry of Agriculture, Forestry, Fisheries and Meteorology National Agricultural Research Institute Non-governmental organisation Participatory plant breeding Pacific Island country Papua New Guinea Participatory varietal selection Random complete block design Sustainable Agriculture and Village Extension Secretariat for the Pacific Community Taro Improvement Project Taro leaf blight The University of the South Pacific Vertical resistance

5 5 1. INTRODUCTION The approach used to evaluate taro germplasm through breeding trials in a particular country will depend on a number of factors, including the existing germplasm regulatory framework, diversity of agroecosytems, and resources and willingness of governments to pursue participatory approaches. For these reasons the Taro Genetic Resources: Conservation and Utilisation (TaroGen) Project understands the need to present guidelines for both conventional and participatory approaches. The objective of these guidelines is to provide researchers and extensionists in the region with information on evaluation of taro. The guidelines describe preliminary selection of progeny from segregating populations but focus specifically on evaluation of more advanced lines in conventional and participatory on-farm trials. Information is not given on crossing techniques or breeding strategies as this is provided in other relevant publications. The guidelines provide evaluation strategies that will be novel for most Pacific Island countries however, if superior genotypes are to be selected for less favourable environments in the region they should be given careful consideration. These guidelines have been prepared for submission to AusAID as a project milestone for TaroGen.

6 6 2. BACKGROUND Taro (Colocasia esculenta) is one of the major root crops in the Pacific Islands and is an important source of food and income. Corms are high in carbohydrates and the leaves are an excellent source of vitamins. It is an important export crop in some countries of the region. In addition to its nutritional and economic importance, taro plays a significant role in the cultural heritage of the Pacific Islands, and is considered an essential component of many traditional ceremonies. Since taro leaf blight (TLB), caused by the fungus Phytophthora colocasiae, first arrived in the region earlier last century, Pacific Island countries have used a few strategies in an attempt to control and prevent its spread. Some fungicides can be used but are generally too expensive for the majority of growers. Breeding plants with resistance to the disease offers the best long-term strategy for the control of the disease but breeding programmes that commenced in the 1980s and early 1990s were not successful, due to lack of funds and staff changes. In 1993, TLB provided dramatic evidence of its impact when it arrived in American Samoa and Samoa. Prior to 1993, taro was the major export commodity in Samoa but within a year of the disease outbreak, production was decimated and incomes severely reduced. The TLB outbreak in Samoa provided a timely reminder of the urgent need to find sustainable long-term measures to control the disease. Consequently, the Secretariat of the Pacific Community (SPC), the International Plant Genetic Resources Institute (IPGRI) and representatives from Pacific Island countries met to devise strategies to help rejuvenate taro breeding programmes and the conservation of taro genetic resources in the region. The outcome of this important meeting was the Taro Genetic Resources: Conservation and Utilisation (TaroGen) Project. TaroGen began operating in 1998 from SPC, Fiji with the support of the Australian Government. TaroGen provides support to breeding programmes in Papua New Guinea (PNG) and Samoa and aims to provide growers with improved varieties to overcome production constraints, especially TLB. Breeding in PNG is implemented through the research programme of the National Agricultural Research Institute (NARI) based at Bubia Agricultural Research Centre (BARC), Lae. The Project provides the assistance of a plant breeder working in collaboration with a national counterpart. In Samoa, TaroGen provides the services of a Programme Coordinator based at the University of the South Pacific (USP). In addition, TaroGen provides opportunities for national counterparts, from PNG, Samoa and Solomon Islands to undertake postgraduate training in taro breeding. The TaroGen breeding programme commenced with a strategy workshop held in Fiji in August 1998 and was attended by project staff, plant breeding adviser Dr Raoul Robinson, and representatives from Fiji, PNG, Samoa, Solomon Islands and the Horticulture and Food Research Institute of New Zealand. The meeting developed a taro breeding strategy for the next three years. During the first year of the project the breeding work in PNG included evaluation of lines from cycles-2 and 3, produced from a previous breeding programme that began in Tests were begun to determine the nature of resistance (vertical versus horizontal) in the original parental or base lines. The breeding work in Samoa during the first year included evaluation of cycle-1 seedlings

7 7 and taro varieties from Palau. To assist the Project in Samoa, a university taro breeders club and Taro Improvement Project (TIP) were initiated. TaroGen has supported two distinct approaches to the evaluation of taro genotypes in the region. In PNG, advanced lines have been selected within a formal or conventional plant breeding framework involving many cycles of selection on experimental stations with minimal consultation with farmers until the final stage of on-farm genotype x environment (G x E) trials. In Samoa, the approach has been to involve farmers in selection of genotypes at an earlier stage and to minimise the number of cycles of selection that occur on research stations. TaroGen believes that the participatory approach is a logical extension of conventional plant breeding and could provide benefits to countries in the region including identification of superior genotypes, quicker access to genotypes and a broadening of the genetic base of production. There is little doubt that conventional plant breeding, using extensive G x E trials, has been successful in improving yield levels of several crops where the target areas or farming systems resemble closely that of research stations. Success has also been achieved in farming systems that can be made to resemble research stations by the addition of inputs. However, close to two billion people are dependent on agriculture that is practiced in unfavourable or marginal environments. The success of conventional plant breeding for farming systems in these environments has been limited and it is generally agreed that the major reason for the limited success of conventional breeding in this context is the G x E interaction. G x E interactions are most important when the ranking of superior genotypes change, or crossover, between environments. The highest yielding genotypes in high-yielding environments will be genotypes that are not superior in low-yielding environments and vice versa. This can lead to the promotion of one or a few varieties, which are widely adapted or can be grown over large areas. The logical interpretation of the GE interaction is promote specific adaptation by selecting genotypes directly in the target location and one way to do this is to provide more genotypes to farmers from which to make selections. This is one of the objectives of the breeding programme in Samoa. There is growing evidence that breeding for unfavourable environments using participatory or decentralised approaches where advanced lines, or even varieties, are presented to farmers at an earlier stage for evaluation can result in farmers making many diverse selections for particular farming systems. Samoa has witnessed the development of a promising participatory plant breeding programme over the last three years. It has involved a wide spectrum of people including university students, farmers, researchers and extension staff. All have been motivated by a desire to work together to help improve the most important crop species in the country. This partnership has been actively supported by TaroGen and it is hoped that similar programmes can be developed in other countries in the region, especially PNG and Solomon Islands, which have considerable agroecological diversity.

8 8 3. GUIDELINES FOR THE EVALUATION OF TARO IN CONVENTIONAL BREEDING PROGRAMMES 3.1 Introduction The stages involved in a conventional taro breeding programme, using the recurrent selection approach (Box 3), are outlined in Figure 1. Box 1. Conventional plant breeding This is a breeding programme located within an institutional setting, and implemented and managed by breeders/researchers. Evaluation of genotypes involves many cycles of selection on experiment stations and improved genotypes are presented to farmers at a later stage of the programme. The initial stage is to create genetic variability from which superior genotypes can be identified. In preliminary and intermediate trials, selected clones are evaluated and those identified as the best are advanced to additional trials. In advanced trials the breeder works with fewer clones but more plants of each. Preliminary, intermediate and advanced trials usually take place on a research station under the supervision of the breeder or researchers. A more accurate assessment of the clones can be made at the Table 1. Requirements for undertaking different trials during taro varietal improvement programme. Trial/ Features Progeny selection Preliminary trial Intermediate trial Advanced trial G X E trial Confirmation trial Location Research Research Station/Farm Station/Farm Farm Farm station station No. of sites No. of clones Plants/ clone No. of rows Expt. Design None None Single rows RCBD 1 RCBD Blocks Reps Person-in charge Researcher Researcher Researcher Researcher Researcher/ Farmer Researcher/ Farmer Evaluator Researcher Researcher Researcher Researcher Researcher/ Farmer 1 Random complete block design Researcher/ Farmer

9 9 advanced trial stage. Clones selected at the advanced trial stage go to on-farm G x E trials at several locations. Again the number of clones evaluated is reduced. On-farm trials can allow a certain degree of participation by farmers and this should be encouraged. The superior clones identified by breeders and farmers are usually selected, named and released. If required, further confirmatory trials can be implemented. The features of the various trials involved in a conventional plant breeding programme are outlined in Table Progeny Evaluation The initial stage in the breeding programme requires the production of new genotypes for evaluation. This is achieved by crossing parents with desirable characteristics to generate recombinants with unique features. During each cycle of crossing, thousands of recombinants, or progeny, are produced. Every individual is unique and only a small proportion will have the desirable characteristics of interest to breeders and farmers. The stages described in these guidelines will help to identify those individuals that are superior. In PNG, the evaluation of progeny usually takes place on an experimental station to ensure effective management and supervision of trials. Initial screening also involves the use of artificial inoculation of pathogens and trials on station can ensure that diseases are not spread unnecessarily to farmer's fields. In Samoa, progeny are usually evaluated on a farmer s field under natural conditions. Distances in Samoa are much less than in PNG so it is easy to locate a trial within reasonable access to breeders and researchers. Breeding blocks are located at USP-Alafua but there is limited land to allow evaluation of thousands of progeny. In addition, USP-Alafua is located in a dry area of the country and is not an ideal place to screen for a disease such as TLB. Locating progeny trials on a farmer s field also provides an opportunity to involve farmers early on. It also allows selection of progeny in areas representative of farming systems in Samoa. It is important to remember that whichever site you choose for evaluation should reflect the biophysical constraints that are faced by farmers. Do not select progeny from trials that occur under optimum conditions through the addition of fertilisers, pesticides and irrigation. If you do, you may select genotypes that won t do well on farmers fields. In certain instances there are exceptions to this rule. In PNG, it is often necessary to spray insecticides for the control of hawkmoths, otherwise damage can be severe. You may not have the option of screening for TLB under optimal wet conditions so it may be necessary to screen progeny using overhead irrigation. Where you locate your trial may depend on what you are selecting for. In the case of TLB, you may want to initially select progeny in an area that is very wet to ensure maximum disease pressure.

10 10 Figure 1. Stages involved in release of new varieties Evaluation of progeny Preliminary trials Intermediate trials Advance trials On-farm Genotype-Environment interaction (G x E) trials Multiplication of selected material Multiplication of selected material Confirmatory farmers field trials Multiplication of selected material New variety recommended Multiplication of selected material Accepted, named and released Distribution

11 11 Obviously the size of the site for evaluation will depend on the number of progeny. In PNG, this can be as many as 10,000 seedlings at every cycle. In PNG, the preferred planting density at the progeny evaluation stage is 0.25 m 2 (0.5 m between rows and 0.5 m between plants). In Samoa, plants are spaced 50 cm apart within rows with 1 m between rows. After every five rows of seedlings a row of a resistant check (control) variety is planted. In PNG, every 500 seedlings are bordered by a row of spreader plants to encourage disease build-up. Two guard rows on each edge are planted to minimise edge effects. If guard rows are not planted, plants at the edge of rows will be more vigorous and higher yielding because of extra space and less competition. Box 2. Spreader rows, guard rows and checks Spreader rows, which are rows of infected plants of a disease-susceptible variety, increase disease levels in the evaluation site. Guard rows are planted at the border of the site to ensure that all evaluation plants are surrounded by four other plants, thereby minimising edge effects. Check varieties of known resistance and susceptibility help to gauge the relative resistance of the progenies. Susceptible checks also provide information on how well a disease has spread throughout the trial site. The site should be hand weeded to minimise phytotoxicity that might arise as a result of using herbicides. Because each seedling planted is an individual, careful attention must be given to labelling. It is desirable to keep populations of each cross separate, although it is not necessary. If one cross is performing remarkably well, and the number of individuals of this cross are not known, the breeder may be tempted to select large numbers of individuals from one cross. Labelling individuals of each cross helps in selecting individuals uniformly and over a wider range of crosses and therefore broadens the genetic base for the next cycle and helps in avoiding in-breeding depression. The easy way to label is to start each cross with a new marker indicating the name of the cross. Labels can be easily lost or damaged. Make sure a permanent plan or map of the trial layout is made. Multiple copies of the plan should be made, kept in a safe place, and distributed to all workers in the programme. A detailed plan can also include landmarks for orientation, and information regarding planting date and other management activities that take place during progeny evaluation. The selection of progeny depends on the goals of your breeding programme. For example, in PNG and Samoa, the principle goal is the selection of clones with horizontal resistance (HR) to TLB, although yield and quality are equally important. In past PNG breeding programmes, parents with wild and immune phenotypes (often associated with vertical resistance, VR) have been used. This type of resistance is dependent on one or a few major genes and provides the resistant plant with complete protection to the disease. The problem with VR is that it can be easily overcome by changes in the pathogen population. HR on the other hand is dependent on many genes, which makes it difficult for the pathogen population to overcome. In PNG, to achieve HR or polygenic disease

12 12 resistance, it has become important to discard all immune types (possibly indicating VR) and highly susceptible progeny at the outset. Box 3. Vertical and horizontal resistance Vertical resistance (VR) is normally controlled by single genes (major genes) and provides complete control against certain races of a pathogen. In a number of cases a gene-for-gene relationship (for every resistance gene in the host there is an equivalent gene for virulence in the pathogen) has been demonstrated and the problem exists that new pathogen races capable of attacking the resistant plants will evolve. For this reason, VR is often referred to as non-durable resistance. Horizontal resistance (HR) is polygenic, controlled by many genes (minor genes). It does not result from a gene-for-gene relationship. It is effective against all races of a pathogen and does not fail like VR, which is why it is referred to as durable resistance. Unlike VR this type of resistance does not give complete control but limits the spread of the pathogen within the plant. The approach to breeding for HR is called population breeding and the technique of recurrent mass selection is used. At each cycle of crossing, the plants that have the highest frequency of polygenes for HR are selected, based on disease levels in the field. These become the parents for the next cycle and by selecting the most resistant offspring the genes for HR resistance are accumulated. Breeding for HR is a cumulative process. Generally 90% of the original population is discarded at this first stage. If the original population is small, the selection frequency can be increased to 20 30%. A selection of about 1000 individuals is ideal. In Samoa, where the initial progeny population is usually smaller, the number of selections is less. In Samoa, there is no history of breeding for VR in taro so all resistance is HR, and it is a matter of discarding the most susceptible and identifying the most resistant. After selecting for disease resistance, emphasis is placed on other characteristics such as vigour, suckering ability, corm colour, shape and weight and resistance to other important pests. This may result in the elimination of a further 50% of the progeny. A final selection of about 500 progeny is entered for the next round of trials.

13 13 Box 4. Screening for resistance to TLB In Samoa, evaluation plots are visually monitored for the first three months to ensure that all plants are exposed to TLB. After this, the extent of TLB on each plant can be quantified at different stages by visually estimating the percentage disease on each leaf. The average percentage disease for each plant is calculated by the total percentage disease for the plant divided by the number of leaves. From this data it is possible to calculate the effective healthy leaf (EHL) number by multiplying the total number of leaves by percentage healthy leaf area for each plant. In addition, information is recorded on leaf size (medium, large and small) and overall plant vigour (high, medium and low). EHL number has provided a simple, effective comparison of clones in Samoa. In PNG, at later stages of the evaluation, disease intensity is estimated by observing the oldest to the youngest fully expanded leaves. The infection ratings are based on lesion size and development assessed on a 0 4 scale, where 0 = Immune (fully expanded leaves free of any visual symptoms), 1 = Trace (lesions <4 mm in diameter), 2 = Flecks (lesions >4 mm in diameter), 3 = Restricted lesion development, and 4 = Unrestricted lesion development. Individual plants of each selected clone are scored accordingly. Each leaf of the test plant is scored and assigned appropriate categories. The disease intensity (DI) of individual plants are calculated using the formula: DI = Σ(scores on n leaves)/n where n = number of leaves. 3.3 Preliminary Trials The previously selected 500 superior clones are now further evaluated in preliminary trials. In addition to dealing with fewer clones it will be possible to evaluate more plants of each clone. Most breeders establish the site for preliminary trials on-station largely for security reasons, but on-farm evaluation that encourages farmer involvement, are another consideration. In PNG, clones are planted in single rows of 3 plants each. The preferred planting density is 0.5 m 2 (0.5 m within rows and 1 m between rows). A row of a local check is used for every 10 rows of clones. The individuals within each row are bordered by spreader rows to encourage disease development. Two rows of spreaders are also used as guard rows at the edges. The trial is performed under natural conditions and is only maintained for

14 14 weeds. Previous guidelines on labelling and plans apply. Trials should be harvested 6 7 months after planting. Although evaluations continue on disease resistance and morphological characteristics, a greater emphasis is placed on yield and eating quality during this stage. However, with the small number of plants per clone, it is not possible to judge these characters very accurately. For this reason, subjective ratings (low, medium and high) are used rather than quantitative measurements. Following preliminary trials a further 75 80% of clones are discarded and about 100 are selected for intermediate trials. 3.4 Intermediate Trials These trials are carried out in a similar manner as preliminary trials but with fewer clones and more plants per clone. The guidelines provided above on husbandry, borders and spreaders, and labelling also apply to intermediate trials. Depending on planting material the trial could be carried out at more sites. Intermediate trials should be harvested 6 7 months after planting. At completion of the evaluation, the 50 top clones from all sites are selected based on disease resistance, yield and other characteristics. 3.5 Advanced Trials The objective of advanced trials is to further short-list the clones, and reconfirm the performance of clones selected in intermediate trials. Advanced trials are usually carried out on-station but may also be located on a farmer's field. The clones are sown in replications and plants/clone are used. Generally three replications are used but more can be used depending on planting material availability. Each replication comprises of 8 10 plants planted in two adjacent rows. Planting density is similar to that used in preliminary and intermediate trials. Local checks are also used in the trial in a randomized manner. Blocks are guarded by spreader and guard rows and the trial is performed under natural conditions and hand weeded. Quantitative data on yield can now be collected for the clones and the results analysed statistically. Advanced trials should be harvested 6 7 months after planting. For eating quality a subjective rating can be recorded or a more detailed evaluation can be collected. At this stage, more tasters are involved (at least 10, covering wider ethnic groups and gender). Additional data can also be collected at this stage such as corm dry weight or the nutritional value of corms. By the end of advanced trials the number of clones selected for further evaluation is reduced to about six or seven. These clones are now used for on-farm trials.

15 Genotype X Environment (G x E) Trials The purpose of on-farm G x E trials is to check the adaptability of selected clones under different agroecological zones or under different environments. For this purpose it is important to determine diverse sites. The adaptability of clones is complex in countries such as PNG and Solomon Islands where diverse environments have influenced cropping patterns and farming systems. The relative performances of taro varieties may vary among environments (location, year, farming practice, etc.) and also in preferences (taste, texture, colour, and smell) according to different ethnic groups. To assess the accurate performance of varieties and their adaptability, G x E trials are important before making general recommendations. These trials will determine the influence of genotype (G), the environment (E), and their interaction in identifying taro genotypes suitable for specific and/or wider adaptation. G x E trials are considered to be national trials and should be located in taro producing areas representing diverse agroecological zones. The resources involved in these trials are much greater than those at previous stages. In PNG and Solomon Islands, travel to sites will involve frequent air travel. Efforts should be made to identify maximum diverse areas within the available budget. If GIS databases or experts in the field of agroecology are available, they should be consulted when choosing suitable sites. In general, sites should be representative of the area of production. It may be desirable to survey potential sites in order to collect information on climate, soils and farmer management practices. The number of sites selected will depend on the diversity of the country and taro growing areas and available budget. In order to implement G x E trials effectively it is recommended that the number of sites is limited to six or seven. The experimental design used in G x E trials is the randomised complete block design (RCBD) preferably using five replications each with 15 experimental plants of a selected clone. If possible seek the assistance of a biometrician when designing trials. In PNG, the preferred planting density is 0.5 m 2 (1m between rows and 0.5 m between plants) but it is important to use whatever spacing is used by the farmers in the target location. A local check variety and the farmers preferred variety should be used as controls. White wooden stakes specifying the name should be placed in front of each clone or variety as labels. Trial plans showing layout, orientation, planting date and other important information should be kept. A sign adjacent to the trial, outlining the design, objectives and implementing agency, can be informative and useful and could create interest among other farmers and community members. Trials should be performed under natural conditions and maintained by farmers using their traditional management practices. Although the farmer generally looks after the trial there should be regular monitoring by the resident scientist or breeder. At least three visits are essential during the trial period when data are collected on various characteristics such as those highlighted in Annex 1. This is also a useful time to get feedback from farmers regarding the clones. The trials are generally harvested at 6 7 months after planting and yield data are recorded. This is an important time to obtain information from farmers regarding eating

16 16 quality. In PNG, farmer evaluation of clone quality is simple, recording whether a farmer likes or dislikes a particular clone and why. These observations can be recorded in a simple data sheet similar to Table 2. Table 2. Data sheet for clone selection showing example of farmer's evaluation process. Selected clone # Preferred Not preferred Why? 1 a Good yield 2 a Good quality 3 a Poor quality 4 a Good shape and quality 5 a Shape of corm not good In PNG G x E trials, technical evaluation concentrates on various morphological characteristics, disease assessments to TLB and other important pests, yield and eating quality (Annex 1). Five data plants are adequate but higher numbers can lead to more reliable results. Above ground traits are recorded at about four months after planting. If resources and time permits, additional data should be recorded around five months after planting. TLB severity should be recorded at four, five and six months after planting (see Box 4). Accurate eating quality assessment is essential in determining palatability and acceptance of a particular clone. Factors that affect palatability in taro include acridity (related to the presence of oxalates), fibre, texture, flesh colour and aroma. In assessing these factors in PNG, two to three corm samples of g fresh weight of each clone are peeled (removing all tissues surrounding the ground tissue), chopped into g pieces, bagged separately in onion bags and cooked in excess boiling water for minutes. A panel of 15 volunteers (generally nominated by the farmer) carry out the assessment. Each variable is given a constant rank value depending on local eating quality preferences. The constant ranks of the different variables should add to a maximum value of 1.0 (Table 3). Eating quality preferences vary from country to country and even within countries and therefore the constant ranks should be altered accordingly. For example in PNG, texture is considered to be the most important variable of quality and is given a rank of 0.5 (50%) followed by acridity (30%), aroma and appearance (10% each). Table 3. Constant ranks given to different eating quality variables in PNG, and exemplary calculation of final value for eating quality parameter. Variable Constant Rank Actual score* Final score Acridity Texture Aroma Appearance Total *Actual score is multiplied by constant rank

17 17 After tasting, the evaluator records a score on an assessment sheet for each of the variables (on the basis of 1 4 scale in order of high to low acceptability). The final score for each variable is calculated by multiplying the constant rank value with the actual score for each variable. The mean of all evaluators is calculated for each variable and the mean of all variables are added to obtain the final value. From this value, a final grade of taro can be calculated (Table 4). Table 4. Grading of taro on basis of final eating quality value Final value Eating Quality Grade of Taro 0-1 I 1-2 II 2-3 III 3-4 IV I = highest grade, IV = lowest grade The selection of a superior clone(s) for recommendation and release will depend on the analysis and interpretation of data recorded from G x E trials. The biometrician who assists with the trial design should be able to help with this. Data is usually subjected to analysis of variance followed by pooled analysis of the data. Guidelines for data analysis are beyond the scope of this document. The clone(s) that is stable (ability of a particular genotype to maintain a near constant phenotype for the character of interest over variable environments) and performs well in all environments is usually selected. Selections based on technical considerations may be complemented with farmer's selections. These clones can be recommended for general release and distribution or can be made available for further on-farm confirmation trials. 3.7 Confirmation Trials and Variety Release If required, additional trials can be used to compare the one or two selected clones with farmers preferred varieties. The farmer s variety and the selected clone(s) are grown in blocks side by side and comparisons are made. A large number of farmers can be identified at this stage and the trials are preferably implemented with extension agents, NGOs or church groups to minimise costs. Trials also provide an opportunity to multiply and distribute the selected clones to other taro growing areas. Once the variety is approved for release by the appropriate authority, the clone is named and officially released. Awareness of the new variety can be raised through extension, media and agriculture shows.

18 18 4. GUIDELINES FOR THE EVALUATION OF TARO IN PARTICIPATORY PLANT BREEDING PROGRAMMES 4.1 Introduction The need for a more participatory approach to plant breeding in Samoa arose as a consequence of informal discussions with farmers who often expressed dissatisfaction with the pace of release of resistant taro germplasm through conventional taro breeding programmes. Researchers at USP were also concerned with the rate at which resistant taro was released through conventional taro breeding and the rigorous testing over several years trying to identify a few clones or varieties that may not meet farmer needs. Evidence from elsewhere suggests that much of the germplasm officially released through conventional plant breeding programmes in developing countries is of limited relevance to farmers and much of the material that is rejected has been found to have subsequent acceptance among farmers. Conventional taro breeding also contributed little to increasing the diversity of taro grown in the country. Genetic vulnerability was the major contributing factor to the devastating TLB epidemic in A participatory approach to plant breeding, involving researchers, farmers and extension staff, was considered as a means to: learn more about what farmers wanted from improved taro varieties and to involve them in the technology development process. At the same time it also provided an opportunity for skills building within the farming community and extension services. Farmers gain an understanding of breeding, disease management and the benefits of diversity, while extension officers are exposed to the latest developments and feedback on new varieties or clones they can use to their benefit in a much wider context; involve many farmers working in diverse environments and providing them with a range of options so they can select the best genotypes for their conditions. This would ensure that farmers gain quicker and wider access to resistant taro, which results in greater field diversity and reduced genetic vulnerability of the crop; strengthen the linkages between researchers, extension staff and farmers; and make more effective use of the limited time and resources of researchers and extension staff, and create more opportunities for the sharing of costs.

19 19 Box 5. Case studies outlining the benefits that can result from participatory approaches to plant breeding. In 1993 the Colombian Agriculture Research Institute (ICA) adopted a participatory approach to its cassava breeding programme. The transition has resulted in more acceptable varieties and quicker adoption rates by farmers. The participatory plant breeding (PPB) approach has meant that breeders can better meet farmer needs. The Sustainable Agriculture and Village Extension (SAVE) programme in Sierra Leone found that when farmers are given access to diverse varieties they demonstrate an acute ability to experiment and share experiences with others. Farmers organised themselves into clubs and experimented with 54 varieties of rice, cassava, sweet potato, oil palm, mango and maize. By 1995, five years after the project had commenced, at least 18 varieties had been adopted. In that same period the number of farmers belonging to clubs had risen to In Latin America, CIALs (local agricultural research committees) were initiated to link farmers with formal researchers and have contributed to a greater understanding of farmer needs. A CIAL usually consists of four farmers selected by the community and draws on the resources of research institutes, universities and NGOs. During the first four years of CIAL development, farmer-researchers have tested around 1,000 varieties of different crops. This has led to the establishment of small-scale seed enterprises selling the preferred varieties, which have been bought by more than 10,000 farmers. Participatory varietal selection (PVS) involves farmers in the selection of finished products or varieties. By contrast, farmers have also been involved in the selection of progenies from breeding programmes, frequently referred to as participatory plant breeding or PPB. PPB can also exploit the results of PVS by using the identified varieties as material for future crosses. PPB has a number of advantages compared with conventional breeding. One of the most important is that G x E interactions are greatly reduced because selection is always in the target area. With horizontal resistance this is critical as observed with the variety PSB-G2 (taro Fili) in Samoa, where it performs well in dry areas but can be affected severely by TLB in wet areas. There is a need for additional varieties capable of coping with TLB in such environments. PPB also reduces the demand on research station land and costs, a major constraint at USP-Alafua. Most importantly, PPB ensures that traits of relevance to farmers are evaluated. Both PPB and PVS also ensure that varieties get to farmers quickly. In conventional plant breeding it may take up to 10 years for a variety to be released to the farming community.

20 20 Box 6. Definition of participatory breeding terms. Participatory varietal selection (PVS) Selection by farmers on their fields of stable varieties or advanced lines from plant breeding programmes. A PVS programme consists of three important components: Finding out what farmers need; Selecting varieties or advanced lines that fit those needs; and Testing those genotypes on farmers fields. Participatory plant breeding (PPB) Farmers are actively involved in the breeding programme and have input to the selection of parents and genotypes from segregating populations. The Plant Breeding Working Group of the CGIAR Systemwide Program on Participatory Research and Gender Analysis for Technology Development and Institutional Innovation further define two categories of PPB: 1. Formal-led PPB Initiated by institutions involved in breeding. Farmers are encouraged to collaborate. 2. Farmer-led PPB Breeding institutes or scientists provide support to existing systems of farmer breeding and selection. Other terminology used includes Participatory Crop Improvement, Farmer Participatory Breeding and Collaborative Plant Breeding. There is considerable time and effort involved in starting a participatory programme of plant breeding. Not all governments or institutes will be receptive to the idea of farmer participation in breeding and it may conflict with already existing regulatory frameworks. Careful consideration of the questions and issues highlighted in Annex 2 may help determine if participatory approaches are required or if there is commitment, and the framework in which it should take place. In Samoa, after consideration of many of these issues it was decided that such an approach would contribute to meeting some of the benefits highlighted above and that the most suitable approach was to use a farmer group. It was felt that the collective effort and organisation of a group working with a common purpose was an effective way of starting a process of participatory and self-reliant development.

21 Taro Improvement Project (TIP) The Taro Improvement Project (TIP), a large farmer group, was initiated at USP in TIP aims to bring together taro growers and provide them with more options for improving production and managing TLB. It represents a partnership between USP research staff, the Ministry of Agriculture, Fisheries, Forests and Meteorology (MAFFM), extension staff and farmers. The project is working with about 25 farmers on the island of Upolu to evaluate introduced taro varieties from Palau, the Federated States of Micronesia and the Philippines. A similar programme has been initiated on the island of Savai i. Initiation of the TIP farmer group was motivated by the potential benefits outlined above and the noticeable success of other similar farmer groups implemented elsewhere to address problems aimed at farming systems improvement. Farmers involved in TIP have participated in evaluation and selection of exotic varieties and also clones from the USP breeding programme. As the programme develops it is planned to involve farmers at earlier stages such as the selection of segregating material. Box 7. What is a farmer focus group? A group of men and/or women who join together to pursue a common interest or problem that will contribute to the improvement of their livelihood. Membership Farmers become members of TIP by either contacting staff at USP or notifying their district extension officer. When a farmer has been selected as a taro grower, he or she agrees to compare taro varieties in a grower participatory research programme. Farmers have been selected from most districts on the island of Upolu. When farmers come to their first TIP meeting they complete an Information Form that provides important background information to those involved in the programme. An example of the TIP Information Form is included as Annex 4. This can be adapted for more diverse agroecosystems to collect useful information on farming systems, farmer profiles, or farmer needs.

22 22 Box 8. Organising a farmer group. Several factors to consider when organising a farmer group: Motivation group members must have the aspiration to come together and work for their own common good. Membership must be voluntary and based on an individual s own motivation. Common interest participants must share a common interest. Composition groups of people that are largely of a similar socio-economic status tend to function best. Size the optimal size of a group is in the range of 10 to 25 members. Larger groups will tend to be dominated by more aggressive members. Rules groups that have been successful tend to put considerable initial effort into clearly defining their objectives and bye-laws. In Samoa, membership is open to all as long as participants agree to collectively evaluate taro, maintain plots and give feedback (Annex 3). Efforts are made to ensure there is good geographical coverage of the island. The group is largely dominated by men which is a reflection of taro cultivation in the country. Where possible, women are encouraged to take part especially in the quality evaluations that are organised at farmers homesteads. Initially there were members who were not as committed as others and tended to neglect their evaluation plots. Decisions regarding their future involvement can be made later. The group ranged in terms of expertise. Some were highly innovative, and some had been major exporters of taro before TLB. Others produced for home consumption and, occasionally, local markets. If farmers come from a range of socioeconomic and farming system backgrounds serious consideration should be given to membership. If the intended target area is large, consideration will have to be given to having more than one group. Extension services The role of the extension service in TIP is to provide a link between researchers and farmers. District extension officers identify suitable farmers for participation in the programme and provide on-going monitoring of on-farm trials. It is difficult, if not impossible, for researchers to maintain daily contact with farmers and this is a function that should be assigned to extension. Extension staff can also provide transport so that farmers can attend monthly meetings. Involvement in the programme provides extension officers with valuable information on new germplasm that can be disseminated beyond those farmers taking part in TIP.

23 23 Facilitator The importance of the personality and attitude of a group facilitator cannot be stressed enough. The skills required are numerous and diverse, covering a broad range of social and technical issues. In Samoa, the programme was able to identify a suitable candidate with extensive experience in participatory methodologies and a strong background in farming systems research who came from a previous donor-funded project and had suitable strengths in both social and agricultural sciences. A facilitator needs to encourage those who are shy and control more aggressive participants while at the same time allowing dialogue to run smoothly. The facilitator must always be open to suggestions and minimise any pre-determined notions that he or she might harbour. Most importantly, the facilitator should have the ability to resolve conflicts that arise. Location A suitable location for all participants must be decided upon. Samoa is relatively small compared to other Pacific Island countries and is easy to select a central location within reach of the most distant participants. USP was the most appropriate location because it was central for everyone and was the main site for breeding activities that were regularly used as field visits. When the neighbouring island of Savai i decided to initiate a second TIP group, it was impossible to accommodate the group at USP because 1) the group would have been too large; and 2) the logistics involved in bringing farmers from another island were overwhelming. The outcome was a decision to share the facilitator between the two groups and locate a second group in Savai i. This problem highlights a very useful point. At the time that Savai i decided to start a second group, the Upolu group was running effectively for over a year. It provided an excellent model on which to base the planned Savai i group. To facilitate the extension of the group idea to Savai i, 10 extension officers were invited from Savai i to take part in a regular TIP meeting to observe how the group operated. On the afternoon of their visit they were taken to three on-farm evaluation sites to observe how trials are laid out and evaluated. All this was done in a single day and provided a strong foundation for the Savai i group at minimal expense. Meetings The frequency and duration of meetings should be decided by the group. In Samoa, one meeting a month was adequate and meeting activities could be completed in two to three hours. In order to maintain interest it was important to supplement meetings with other activities such as field visits and taste tests.

24 24 Box 9. Organising meetings. At USP it was decided at the outset by the group to meet once a month. TIP meetings are held at USP but could be held at any convenient location such as a church, school or community hall. For a change of location TIP has organised meetings at field sites that allows farmer-to-farmer extension. Meetings usually run for two hours depending on discussions, and members are greeted with refreshments. Farmers without transport arrange with their local extension agent for a ride to meetings. Meetings commence with a prayer before discussion of the minutes and other issues. The group facilitator must be careful not to allow anyone person to dominate the meeting. Topics of discussion are recorded and minutes produced for the next meeting. Most meetings conclude with a taste test using taro corms brought in by group members and a trip to observe some aspect of the breeding programme on campus. Minutes TIP maintains detailed minutes of group discussions that are distributed to all participants at the start of a meeting. Minutes are printed in English and Samoan. Information is also included on the results of taste tests and any data that is presented on taro evaluation. The minutes also provide an accurate record of any important decisions taken during a meeting. The minutes therefore are a useful record of the evaluation process. It is important to nominate someone to document the minutes. In Samoa, a research officer from the University was given this task. Box 10. Ranking Farmers who attended one of the early TIP meetings were asked to rank the characteristics they thought most contributed to making the ideal taro. Some of the characteristics that were given were obvious but long shelf life was a characteristic that had not been considered before by breeders in Samoa. Further discussion revealed that taro Fili (PSB-G2) had too short a shelf life for overseas markets. This prompted breeders at USP to test advanced lines for storability. Similar exercises have been carried out by farmers to rank their general agricultural problems and their varietal preferences. 1. Good eating quality 4. Tender leaves for luau (vegetable) 2. TLB resistance 5. Long shelf life 3. High yield 6. Vigorous growth Size There are different opinions regarding the size of a group. Some practitioners recommend limiting participation to 20. The maximum manageable size from experience in Samoa is 20 to 25 participants, of which 15 to 20 are usually farmers and the remainder are researchers and extension officers. Do not underestimate the amount of resources required to run a group of this size. Large groups tend to be dominated by the more