Development and deployment of maize hybrids with desired farmer preferences and resistance to foliar diseases for the mid-altitude areas of Kenya

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1 Development and deployment of maize hybrids with desired farmer preferences and resistance to foliar diseases for the mid-altitude areas of Kenya Introduction Leley, P.K and Njoroge, P.K Maize is the third most important cereal globally, after wheat (Triticum aestivum L.) and rice (Oryza sativa L.). As a staple, maize dominates the food economy of eastern and southern Africa, where it is by far the dominant staple crop grown by the vast majority of rural households. In Kenya, it accounts for over 80% of the total cereals consumed (Mugo et al. 2002). Therefore, successful grain production of this crop is the key to the country s food security. In Kenya, lack of maize is synonymous to food insecurity. Maize is the most consumed cereal with a per capita consumption of 125 kg per year. Kenya population now stands at 45 million people and therefore the country needs a minimum of 4 million tons of maize per year (Anon 4, 2010). Maize is consumed by both the rural and urban population. ranging from the highlands to It is grown in diverse agro-ecological zones, lowlands and the semi-arid areas of Kenya. Maize is grown on total land area of 1.5 million hectares. The total production per annum is 2.8 million tons. Low total harvest is caused by low average maize yield which stand at 1.5 tons ha -1. This is way below the world average of 4 ton ha -1. Most of the maize (70-80 %) is produced by small-scale farmers Low yield on-farm is attributed to constraints on farm that limit farmers access to inputs [seeds and fertilizer] and lack of information on improved varieties (Anon 3, 2007). Research has also shown that the yield potential of 6-8 tons ha -1 is achievable with improved varieties, when the production constraints are minimized. The yield potential of maize hybrids in Kenya is at the lower side because the genetic variability of maximum yield has not been fully exploited. In the US and South Africa the minimum research yields are tons ha -1. In general the prevalent maize constraints farmers are faced in maize production are poor access to improved varieties, foliar diseases, pests, low soil fertility, drought and lack of information on availability and low farmer preferences of improved maize varieties. Farmers in the mid-altitude areas experience constraints resulting in low production in maize (<1.5 tons ha -1 ) due to the prevalence of maize streak virus disease (MSV), turcicum leaf blight and gray leaf spot, stem borers, drought, striga parasite and

2 the new emerging maize lethal necrosis (MLN) disease (Anon 1, 2002; Okori et al., 2003). Of these problems facing maize farmers, two diseases maize streak virus (MSV) and maize lethal necrosis (MLN) can causes yield losses of up to 100%. In less than 2 years ago, the latest threat to maize production is a new disease, the maize lethal necrosis disease which in is causing havoc to maize production in parts of eastern, and rift valley provinces of Kenya. This has resulted in a new government directive and requirement to develop strategies to combat the spread of the disease (Anon 2, 2006; Wangai, et al., 2012). This necessitates the development of maize varieties which are resilient to these constraints, with a high genetic potential, combined resistance to at least two diseases which are the maize streak virus, and maize lethal necrosis disease. These hybrids must also fit in maturity groups of days for the transitional zones (Thika, Mwea, Kangundo, Siaya, Homabay) and days for mid altitude zones (Kiambu, Murang a, Nyeri, Embu, Meru, Bomet, Nakuru, Kericho) and days for spill over to the moist transitional zones of Western Kenya. MATERIALS AND METHODS Breeding Nurseries During the short rains of October December 2015, two nurseries for generation advance were established at Muguga for generation advance from S 4 to S 5 of DRT/MSV lines at Muguga. Only 300 lines had enough seed and thus were planted in single row per line (Plate 1 and 2). The crop was harvested, threshed, seed processed, dressed and stored. Plate 1. Kiboko Breeding Nursery- Plate 2. Breeding nursery Muguga Kiboko

3 During the long rains of April June 2016, two nurseries were established both at Kiboko and Muguga for generation advance from S1 to S2 for MLN segregating populations. These nurseries were weeded and top dressed. The kiboko nursery is at booting stage while the one at Muguga is at L6 vegetative stage. Pollination will be done by hand using the standard procedures. Formation of new crosses/hybrids There are already existing elite germplasm/inbred lines developed at KALRO Muguga South and MLN lines sourced from CIMMYT. These were planted during the short rains of October December 2015 at both Muguga and Kiboko KALRO Centres. The lines planted included MSV, GLS, MLN, Drought (DRT), and Low N resistant/tolerant (Plate 3). At flowering, they were crossed in all possible combinations/diallel way in order to form both single and three way cross. Pollination was done by hand using the recommended procedures. During the reporting period, these crosses were harvested at both Muguga and Kiboko breeding nurseries. The seed from these harvests were processed, dressed with insecticide and kept in the cold room. Plate 3. Crossing block - Kiboko During the long rains of April June 2016, two crossing block nurseries were established both at Kiboko and Muguga in order to form both single and three way cross. The lines planted for making crosses included MSV, MLN and GLS lines. Both the nurseries were weeded and top dressed. The kiboko nursery is at booting stage while the one at Muguga is at L6 vegetative stage.

4 Screening germplasm/lines for MSV and MLN disease resistance During the short rains of October December 2015, a total of 430 germplasm/lines consisting of 120 single crosses, 180 three way crosses and 130 double crosses from the KALRO Muguga maize breeding program were submitted to the MLN disease screening facility at KALRO Naivasha Dairy Research Institute jointly run by KALRO and CIMMYT. These crosses were artificially inoculated twice. At the same time one onfarm trial was established at Bomet consisting of a total of 500 single and double crosses. Both trials were laid out in an incomplete block design and replicated twice. Data was collected on both disease scores and yield. Disease scoring was done at vegetative stages. Harvesting of the trials was also done (Plates 3 and 4). Plate 4. Yield data taken Naivasha Plate 5. Gran Moisture measured - Naivasha During the long rains of April June 2016, a total of 170 three way crosses and 80 inbred lines were submitted to the MLN disease screening facility at KALRO Naivasha Dairy Research Institute. These crosses and lines were planted and will be inoculated twice. The trial was laid out in an incomplete block design and replicated twice. Data will be collected on disease scores and yield.

5 Results and Discussion Formation of new crosses The nurseries in both Kiboko and Muguga have been harvested and 500 crosses were realized consisting of Single crosses, three way crosses and Double crosses. These crosses will be evaluated for both yield and MLN disease resistance in at least three locations. Screening for MLN resistance Bomet Data entry and analysis has been undertaken and promising germplasm selected. All the 18 landrace populations were all susceptible to the MLN disease and thus will be discarded as they will not be useful in the development of MLN disease resistant varieties. The disease scores ranged from 2.25 to However, 68 single crosses screened for MLN resistances had a disease severance score ranging from 2 3 (Table 1). Thus showed moderate resistance to resistance to MLN disease. These crosses will be used for further breeding work and evaluated for yield across locations. These scores are generally lower than those in Naivasha. This is because, there was high disease pressure in Naivasha than in Bomet since the crosses were artificially inoculated as opposed to natural inoculation in Bomet which case there may be escapes. Table 1. Crosses with scores ranging from 2-3. No. Entry Code Dscore No. Entry Code Dscore No. Entry Code Dscore 1 SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN

6 13 SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN Analysis of Variance: Yield The yield for the crosses ranged from 0.73 to 4.25 T Ha -1. The grand mean yield for the entries was 1.78 T Ha -1. There was significant differences at p<0.05 for Yield (Table 2). The CV% was 42.9 which shows that there a lot of variation as attested by wide range in yield for the crosses. Also when there is stress, in this case the disease, the CV is usually is high. The yields are higher than those in Naivasha. This is because, there was high disease pressure in Naivasha than in Bomet since the crosses were artificially inoculated as opposed to natural inoculation in Bomet in which case there may be escapes. Table 2 ANOVA Table - Yield Variate: Yield: T Ha -1 Grand mean: 1.78 Source of variation d.f. s.s. m.s. v.r. F pr. REP ENTRY No * Residual Total CV% 42.9 LSD * Significantly different at p<0.05

7 Naivasha Out of the lines screened for disease resistance in Naivasha, only 24 lines had a disease severance scores ranging from 2 3. (Plate 6 and Table 3). These lines will be seed increased and used for further breeding work. Plate 6. One line showing resistance Susceptible line Resistant Line Table 3. Inbred lines showing moderate to resistance to MLN disease No. Pedigree Score No. Pedigree Score 1 MUL-MLN MUL-MLN MUL-MLN MUL-MLN MUL-MLN MUL-MLN MUL-MLN MUG MUL-MLN MUL-MLN MUL-MLN MUG MUG DR/MSV-MLN MUL-MLN MUL-MLN MUL-MLN DR/MSV-MLN MUL-MLN DR/MSV-MLN MUL-MLN DR/MSV-MLN DR/MSV-MLN MUG

8 As for the single crosses, the Mean disease scores ranged from 3 to 4, but 0nly 24 crosses had a score of 3 to 3.25 and are shown in the table 4 below. Thus showed moderate resistance to MLN disease. These crosses will be used for further breeding work and evaluated for yield across locations. These disease scores are higher than those in Bomet. This is because, there was high disease pressure in Naivasha than in Bomet since the crosses were artificially inoculated as opposed to natural inoculation in Bomet in which case there may be escapes. Table 4. Crosses with scores of 3 to Entry Code D.Score Entry Code D.Score Entry Code D.Score SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN SC-MLN Analysis of Variance: Yield The yield for the crosses ranged from 0.64 to 1.92 T Ha -1. The grand mean yield for the entries was T Ha -1. There was no significant differences at p<0.05 for Yield (Table 5). The CV% was 42.9 which shows that there a lot of variation as attested by wide range in yield for the crosses. Also when there is stress, in this case the disease, the CV is usually high. The yields are lower than those in Bomet. This is because, there was high disease pressure in Naivasha than in Bomet given that the crosses were artificially inoculated as opposed to natural inoculation in Bomet in which case there may be escapes.

9 Table 5 ANOVA table - Yield Variate: YIELDT/HA Grand mean Source of variation d.f. s.s. m.s. v.r. F pr. REP ENTRY Residual Total LSD CV% 48.6 Correlation The correlation between disease scores and yield for Bomet and Naivasha are o.5 and -0.6 respectively (Tables 6 and 7). This means that the lower the disease scores, the higher the yield. This is largely due to the reduction of the photosynthetic area due to high disease pressure thus the leaves die. Table 6 Correlation between yield and disease scores - Bomet D Score 1 - YIELD:T/HA Table 7 Correlation between yield and disease scores - Naivasha D_Score 1 - YIELDT/HA

10 Conclusion and Way Forward The selected lines and single crosses which showed moderate resistance to resistance to MLN disease will be seed increased and used for future breeding work. As a way forward, the following activities will be undertaken during the next planting season: Screen new crosses formed for MLN, MSV, GLS and turcicum blight resistance Breeder seed production Enter promising hybrids at NPT Promotion of released varieties through farmer field days, agricultural shows and on-farm demonstrations References Anon 1, Annual Report 2002, KARI-Muguga South. Anon Annual Report 2006, KARI-Muguga South Anon Annual Report 2007, KARI-Muguga South. Anon Economic Review of Agriculture Central Planning and Project Monitoring Unit (CPPMU) Ministry of Agriculture, Kenya. Mugo, S, J. Songa, H. DeGroote and D. Hosngton Insect resistance maize for Africa (IRMA) project: An overview. Syngeta Symposium, Washington DC. June 25 th USA. Okori, P., J. Fahelson, P. R. Rubaihayo, E. Adipala and C Dixelius Assessment of genetic variation among East African Cercospora zeae maydis- populations. African Crop Science Journal. 11: Wangai A.W, M.G. Redinbaugh, Z.M. Kinyua, D.W. Miano, P.K. Leley, M. Kasina, G. Mahuku, K. Scheets, and D. Jeffers First Report of Maize chlorotic mottle virus and Maize Lethal Necrosis in Kenya. Plant Disease. 96 (10) 1,582.3.