Cane yield attributes and heritability of juice quality characters in sugarcane under moisture deficit conditions

Transcription

1 Sugar Tech (2009) 11(4) : RESEARCH ARTICLE Cane yield attributes and heritability of juice quality characters in sugarcane under moisture deficit conditions M.N. Ishaq G. Olaoye Received: 18 August, 2009; Accepted: 20 October, 2009 Abstract Development of drought tolerant sugarcane varieties for cultivation in drought prone ecologies of the Nigeria savannas is prerequisite to attain self-sufficiency in sugar production in Nigeria. To this end, bi-parental progenies from four sugarcane crosses involving two drought tolerant and two moderately drought susceptible clones were assessed along with their parents for their drought tolerance capacity using three moisture regimes well watered, moderate and prolonged drought stress respectively. Almost all the traits investigated in the genotypes remained unaffected by moderate drought stress except cane yield which was reduced by 2-35% in the parents and by 5% in one cross. Prolonged drought stress reduced cane yield by 6-21% in the parents and by 13-21% in the crosses. Differences for juice quality attributes (except refractometer brix and % fibre) were significant under prolonged drought stress. Both additive ( 2 ) A and dominance ( 2 D) genetic variance estimates differed significantly for juice quality attributes but estimates obtained for 2 D were larger in magnitude than 2 indicating the A usefulness of specific crosses in breeding for drought tolerance. Progenies from drought tolerant parents exhibited positive heterosis over mid-parent values for stalk length and cane yield under moderate drought stress condition confirming the presence of non-additive gene action for these traits in the populations. Heterosis over the better parent were, however, negligible or negative for most of the characters. M.N. Ishaq ( ) National Cereals Research Institute, Badeggi, PMB 8, Bida, Nigeria mnishaq2003@yahoo.com G. Olaoye Department of Agronomy, University of Ilorin, PMB 1515, Ilorin Nigeria Keywords Sugarcane, drought stress, cane yield, juice quality, heterosis Introduction Sugarcane (Saccharum hybrids L.) is the major raw material from which refined sugar is manufactured and is a source of revenue for many resource-limited sugarcane growers in the Nigeria savannas where most of the sugar estates are located. However, the ecology is characterized among others by erratic rainfall distribution and/or abrupt cessation of rains during the growing season, thus constituting the greatest hindrance to increase sugarcane production in the country (Olaoye, 1999). Low output of cane and subsequent reduction in sugar per unit area, as well as low sugar recovery from net weight of cane has been attributed to severe drought stress (Moore, 1987). However, studies have also shown that the capacity to tolerate drought is genotype dependent (Abayomi and Mobolaji, 1995; Olaoye, 2005, 2006) and so can be bred. Breeding for high yield in drought stress environments can be achieved either by selecting for characters that increase yield under moisture deficit (Parsons, 1979) or by incorporating drought tolerance trait into an existing breeding programme (Richards, 1989). An alternative approach is to use genotypes with desired expression of the trait as parents in hybridization so that selection can be made in the progenies under adverse conditions likely to be encountered by the genotypes under cultivation. A earlier report which assessed the performance of four sugarcane clones and their bi-parental progenies under well watered and moisture deficit (Ishaq and Olaoye, 2006) revealed

2 Sugar Tech (2009) 11(4) : preponderance of additive genetic variance ( 2 A ), consequently high narrow sense heritability (h 2 N) estimates in the progeny populations for cane yield and yield components under moisture deficit. The progenies showed superiority over their parents for cane yield and its components of stalk length, number of stalks per stool and single stalk weight. In other words, faster progress could be made in the development of high sugarcane varieties that combine high productivity with drought tolerance when selection is practiced under moisture deficit. However, it is also necessary to determine the extent of reduction in cane yield and quality attributes resulting from exposure of genotypes to either moderate or prolonged moisture deficit. This will provide information on the length of drought stress that sugarcane varieties can tolerate without adverse effects on their yield potential. This part of our study reports on reduction in cane yield and associated traits in four sugarcane clones and their bi-parental progenies when exposed to moderate and prolonged drought stress. The second objective was to determine the inheritance of juice quality attributes under prolonged drought stress, which is often the characteristics of the Nigeria Savannas where majority of the sugar estates are located. Since heterosis and maximum variability is usually displayed in the F 1 progenies of a cross between two parental clones in sugarcane, the third objective was to gain information on the expression of heterosis for cane yield and associated traits in the populations under moisture deficit. Materials and Methods Description of genetic materials The genetic materials comprised two drought tolerant (KD- 01 and F141) and two 2 moderately drought susceptible (Co453 and Co331) sugarcane clones (Ishaq and Olaoye, 2006). The four clones were selected from 30 sugarcane accessions which were previously evaluated in the screen house and field condition under well-watered and moisture deficit at the National Cereals Research Institute (NCRI), Badeggi, Nigeria (Ishaq et al., 2008). Clones KD-01 and Co453 have been classified as females while F141 and Co331 are males on the basis of their pollen fertility (Ishaq, 2005). Methodology Crosses were effected between the four parents in the NCRI s, screenhouse, Badeggi, Nigeria, during the growing season as shown below KD-01 x F141 (Tolerant x Tolerant) KD-01 x Co331 (Tolerant x Moderately drought susceptible) Co4543 x F141 (Moderately drought susceptible x Tolerant) Co453 x Co331 (Moderately drought susceptible x Moderately drought susceptible). Fuzz (sugarcane seeds) which were collected from the female parents at ripening were sown individually into trays 50m x 50m x 4.5m in the screen house and covered with polythene sheets to increase the humidity and temperature. This was done to enhance optimum germination. Seedlings were maintained in the trays until one month of age when they were transplanted into polythene bags and raised till three months of age before transplanting to the field. At transplanting, ten vigorous seedlings were selected per cross and were evaluated along with the four parents in the field for their drought tolerance capacity using three moisture regimes - well watered, moderate drought stress and prolonged stress, respectively. The planting materials used were three singleeye cane setts planted in a three replicate randomized complete block design in the field. Each plot consisted of single row, 2m long, spaced 1m apart and 1.5m between the rows. Plantings were carried out in February and December of 2002, respectively at the Institute s Research Farm, Badeggi, Nigeria. With respect to planting made in February 2002 hereafter referred to as moderate drought stress, water was withdrawn for four weeks after 10 weeks of growth while for the December 2002 planting (i.e. prolonged drought stress), moisture stress was imposed for eight weeks also after 10 weeks of vegetative growth. However, the well-watered plots (control) for each experiment received regular irrigation throughout the duration of both experiments. Rainfall is usually negligible between November and May at Badeggi where the study was conducted (Table 1). Therefore, crops in the stressed fields only survived on residual moisture in the soil. In order to monitor the soil moisture situation during each of the stress periods, a sampling core of 5cm x 5cm was used to collect soil at 4-day intervals from 0-15cm and 15-30cm depth respectively. The values were thereafter used to plot graphs that depict trend in the available soil moisture during the stress period (Fig. 1 and 2). Water was re-applied to the stressed fields after the duration of each stress period. At maturity (i.e. 12 months after planting), data were collected from five random plants in each plot on stalk length, stalk diameter, single stalk weight and number of internodes/ stalk. Other parameters included number of stalks/stools, leaf length, leaf width, refractometer solids (%Brix) and number of millable stalks from which cane yield/plot was estimated. Stalk length was measured in centimeter (cm) as the distance from the base of the stalk to the top most visible node while stalk diameter (cm) was measured from the fifth internode of the main stalk with the venier caliper. Refractometer brix was also taken from the fifth internode of the main stalk while leaf area

3 362 Sugar Tech (2009) 11(4) : Table 1. Climatic data for Badeggi (Nigeria) during the filed screening of four sugarcane clones and their bi-parental progenies in 2002 and Rainfall (mm) Temperature o C (cm 2 ) was estimated as the product of the length and width of the leaf using the formula ¾ (L x B) where L = Length of the leaf, B = Width of the broadest part of the leaf. Juice quality analyses were also carried out in the laboratory from five random stalks/plot. The parameters included brix, purity, polarity, fibre content and dry matter content, all expressed in percentages (%). Commercial cane sugar (CCS) was thereafter calculated as CCS = [Recovery x yield/100] where Recovery = [S-0.4 (B-S) x 0.73] B = Corrected brix (Laboratory brix) and S = Sucrose in juice (Verma et al., 1987), Relative Humidity (%) Evapotranspirati on Pan (mm) Minimum Maximum Month November December January February March April May Data collected for both experiments were subjected to separate analyses of variance except that data for well watered treatment for the two plantings were pooled together before analyses. Pertinent means were separated by the use of least significant difference (LSD) according to Steel and Torrie (1980). Percentage reduction in cane yield and associated traits due to exposure of genotypes to moderate and prolonged drought stress conditions were computed as a proportion of cane yield in a particular moisture deficit to the well watered condition. The components of variances and heritabilities for juice quality parameters were estimated using parent-offspring regression analysis (Hallauer and Miranda Fo, 1984). The linear regression model is: Y i = a + bxi + ei where Y i = performance of progenies of the ith parent a = mean performance of all parents evaluated b = linear regression coefficient Xi = performance of i th parent ei = experimental error associated with measurement of X i X Y XY Cov(op) n n 1 where; Cov (op) = covariance of offspring on parents X = mid-parent value Y = progeny value 2 A = 2Cov (op) i.e. Cov (op) =½ 2 A h 2 b Cov(op) 2 i.e. mid-parent offspring regression δ X 2 = D 2 - G 2 A 2 and A 2 = additive and dominance variance estimates D respectively. 2 = genotypic variance G h 2 = heritability in narrow sense 2 = phenotypic variance of mid-parents X Standard errors S. E. for additive variance = S. E. for dominance variance = XY S. E. for heritability = 2 X (Halluer and Miranda Fo, 1980) 2 δ X 2 MSe r Heterosis was determined as percent (%) difference of the progenies from either the mid-parent (MP) or better parent (HP) values according to Falconer (1989) as [ F1 Mid Parent] Mid Parent heterosis % x Mid parent Better parent heterosis % Results 100 [ F1 Better Parent] Better Parent x100 Cane yield and related traits in parents and their progenies under the different irrigation treatments are presented in Table 2. Significant differences were observed among the genotypes for stalk length, stalk diameter and single stalk weight under well-watered. However, the genotypes were similar for other characters. Progenies of cross KD-01 x F141 had longer stalks than the maternal parent (KD-01) but were shorter than their paternal parent under well watered condition. The second

4 Sugar Tech (2009) 11(4) : Soil moisture content Soil moisture content Days after induced moisture stress Fig. 1. Soil moisture regimes at two different soil depth in the stress field (2002) Weeks after induced moisture stress Fig. 2. Soil moisture regimes at two different soil depth in the stressed field (2003) Table 2. Cane yield and associated traits in four sugarcane clones and their bi-parental progenies under three different moisture regimes (Badeggi, Nigeria). Stalk length (m) Stalk diameter (cm) Single stalk weight (kg) Leaf area (cm 2 ) 10 3 %Brix Cane yield (kg/plot) Genotype WW MS PS WW MS PS WW MS PS WW MS PS WW MS PS WW MS PS Parents* KD Co Co F Progenies KD-01 x F KD-01 x Co Co453 x F Co453 x Co LSD (5%) ns ns 0.24 ns ns NS ns 1.41 ns ns CV (%) * First parent in a cross combination designates female. WW = Well-watered, MS = Moderate drought stress, PS = Prolonged drought stress. maternal parent (Co453) had longer stalks than those of the progenies involving both paternal parents. Clone Co453 had wider stalk girth than its progenies from the cross Co453 x F141 and Co453 x Co331 but progenies of the cross combinations Co331 had values similar to that of the paternal parent. All clones except Co331had higher single stalk weight than their progenies. Although the genotypes did not differ for refractometer solids (%brix), two of the parents had higher values than their progenies except that progenies of cross Co453 x Co331 ranked second for this trait. The parents also had higher cane yield than most of their progenies, except that those of the cross KD-01 x F141 had higher cane yield than Co453 and Co331 as well higher than all other progenies. The genotypes differed significantly under moderate drought stress condition for almost all the characters except stalk length and stalk diameter (Table 2). Clones Co453 and KD-01 had higher leaf area than their progenies derived from crosses Co453 x F141, Co453 x Co331, KD-01 x F141 and KLD- 01 x Co331, respectively. Clone F141, which ranked second for sucrose content among the parents, also had higher value than either of its progenies in both cross combinations while cane yield in progenies involving clone F141 and the other two maternal parents were intermediate. Progenies of cross KD-01 x Co331 yielded higher than either parent but those of Co453 x Co331 yielded lower than either parent. Significant differences were also observed among the genotypes for single stalk weight, leaf area and cane yield under prolonged drought stress (Table 2). Cane yield under this condition was higher in the parents than in their progenies under prolonged drought stress except KD-01 x Co331. Clone KD-01 had higher single stalk weight than its progenies. Similarly, clone Co453 had higher single stalk weight than the resulting progenies from the two paternal parents (Co453 x F141 and Co453 x Co331). Progenies of cross KD-01 x F141 had larger leaf area for photosynthetic activity than either parent. However, one of the paternal parents (Co331) had wider leaf area than its progenies regardless of the maternal parent. Although the genotypes did not differ for sucrose content,

5 364 Sugar Tech (2009) 11(4) : Table 3. Reduction (%) in cane yield and associated traits in four sugarcane clones and their bi-parental progenies under moderate and prolonged drought stress conditions (Badeggi, Nigeria). Stalk length Stalk diameter Single stalk weight Leaf area Refractometer brix (%) Cane yield Genotype MS PS MS PS MS PS MS PS MS PS MS PS Parents* KD Co Co F Progenies KD-01 x F KD-01 x Co Co453 x F Co453 x Co * First parent in a cross combination designates female. +; Character not affected by moisture deficit in the genotype. MS= Moderate drought stress, PS = Prolonged drought stress. the progenies had higher values than their parents. Conversely, the parents had higher cane yield than their respective progenies with those of cross Co453 x Co331 yielded significantly lower than three of the parents. Almost all the traits investigated in the genotypes remained unaffected by moderate drought stress except leaf area and cane yield (Table 3). Cane yield was however reduced by prolonged drought stress except in one clone Co331 and its progenies (KD-01 x Co331). Cane yield was reduced by between 2 and 35% in the parents under moderate drought stress and by 6-21% under prolonged drought stress. All progenies except those of the cross between the two moderately drought susceptible parents (Co453 x Co331) maintained their yield potential under moderate drought stress. Reduction in cane yield of 5% under moderate drought stress and 21% under prolonged drought stress were recorded in the progenies of this cross. One of the drought tolerant parents (F141) exhibited reduction for almost all the traits except for sucrose content under moderate drought stress. Refractometer brix remained largely unaffected by moderate drought stress except in parental clone KD-01 but reduced by between 0.61% (Co331) and 18% (KD-01) under prolonged drought stress. Juice quality attributes in the parents and their progenies differed significantly when genotypes were exposed to prolonged drought stress except that refractometer brix and %Fibre remained unaffected (Table 4). One parent (KD-01) was superior to others for juice purity and the value was significantly higher than those of the progenies regardless of the paternal parent. However, population derived from cross Co453 x Co331 was superior for %Purity than both parents. Clone KD-01 also had a significantly higher value than the progenies. Crosses involving Co453 as the maternal parent were superior for %Polarity than their respective parents, which may indicate higher heterosiis (%) for this character in the crosses. Co453 had higher dry matter content, which was significantly superior to those of other parents and its progenies in both cross combinations. Dry matter content was higher in parent clone Co331 than in the progenies. Clone F141 had higher commercial cane sugar (CCS) than its progenies as well as the other genotypes. Population derived from cross KD-01 x Co331 however had higher sugar yield (i.e. CCS) than both parents. The parents possessed higher brix content than their progenies although the progenies were superior for most part for juice quality (polarity). Low values were recorded for commercial cane sugar (%) in all the genotypes under prolonged drought stress with parental clone Table 4. Juice quality characteristics in four sugarcane clones and their bi-parental progenies under prolonged moisture stress (Badeggi, Nigeria). Genotype Brix (%) Purity (%) Polarity (%) Fibre (%) Dry matter (%) Commercial cane sugar (%) Parents* KD Co Co F Progenies KD-01 x F KD-01 x Co Co453 x F Co453 x Co LSD (5%) ns ns CV (%) * First parent in a cross combination designates female.

6 Sugar Tech (2009) 11(4) : Table 5. Estimates of genetic parameters and heritability for juice quality characteristics in four sugarcane clones and their bi-parental progenies under prolonged moisture stress (Badeggi, Nigeria). Juice characteristics Additive variance ( 2 A) Dominance variance ( 2 D) Narrow sense heritability (h 2 ) 2 A 2 D Brix% Purity (%) Polarity (%) Fibre (%) Dry matter (%) Commercial cane sugar (%) * Estimates larger than twice the standard errors are significant F141 and its progenies derived from the cross KD-01 x F141 ranking top among the genotypes. Additive genetic variance ( 2 ) estimates were significant A for all quality characters except refractometer brix (Table 5). Similarly, dominance variance ( 2 D) estimates were significant for quality parameters except for refractometer brix and fibre content. However, dominance variance estimates were larger in magnitude than the additive variance components for all the quality characters. The ratios of the variances which were also positive for all quality parameters, were greater than unity for both refractometer brix and CCS. However, narrow sense heritability estimates ranged from very low in %Fibre (0.06) to moderate in %Purity (0.45). Estimates of heterosis (%) over mid or better parent for cane yield and yield components were for the most part significant for all the characters although many of the values were also negative (Table 6). Progenies from either the resistant male (F141) or female (KD-01) parents exhibited positive heterosis over mid-parent values for stalk length and cane yield under moderate drought stress condition. The opposite was the case for progenies from the moderately drought susceptible parents (Co331 and Co453). Hybrids from resistant parents similarly had significant and positive mid-parent heterosis for cane yield components such as number of stalks/ stool and number of stools/plot (data not shown), stalk length and brix respectively under prolonged drought stress. Heterotic values over the better parent were mostly negative except in few cases such as for stalk length (for two crosses) and refractometer brix (all crosses) under prolonged drought stress. However, these positive values were low. Discussion Sugarcane being polyploid and highly heterozygous, maximum variability is expected from the F 1 of a cross involving two parents of contrasting characters (Olaoye, 2001). Under moderate and prolonged drought stress conditions, significant differences were observed among the progenies and their parents for cane yield and its components, which is an indication of genetic variability, which existed in the different populations thereby providing opportunity for carrying out selection between and within populations in the progenies for drought tolerance. Comparison of performance of genotypes in well-watered and moisture deficit showed that drought tolerant clones (F141 and KD-01) exhibited potential for higher cane yield in both environments. Their progenies were also superior for important yield components of stalk length and single stalk weight under prolonged drought stress. Clarke et al. (1992) observed that relative yield performance of genotypes in moisture deficit and well-watered environments should be the starting point in identifying traits related to drought tolerance and selection of desired genotypes. In the present study, the varieties selected as tolerant clones exhibited similar performances for important yield components like stalk length and single stalk weight in both well-watered and moisture deficit conditions. Therefore, they can be used as parents for development of high yielding varieties for cultivation in both moisture stressed and unstressed environments. Estimates of reduction in cane yield under moisture deficit should provide an index of stability of genotype performance in favourable and unfavourable growing environments. Reduction in cane yield and yield components did not follow a definite trend that could be attributed solely to genetic constitution of the parents used in the crosses. For example, while one of the drought tolerant parents (F141) exhibited reduction in almost all the traits investigated under moderate drought stress, a moderately drought susceptible clone (Co331) with lower cane yield across irrigation treatments, had stable yields under the two moisture deficit conditions except for refractometer brix under prolonged drought stress. However, populations derived from crosses involving F141 (as pollen parent) maintained their performance for cane yield and sucrose content under moisture deficit conditions. Reduction in cane yield and sugar content is more frequent and severe when drought stress occurred during the period which had the highest total evapotranspiration (Wiedenfield, 2000). However, sugarcane varieties which have high transpiration rates in early morning hours when water conditions are favourable, followed by a rapid closure of stomata and decreased transpiration rate during moisture stress, have been associated with high cane yield in areas with deficient soil moisture (van Dilewijn, 1952). In otherwords,

7 366 Sugar Tech (2009) 11(4) : the factors responsible for differential response of sugarcane genotypes to moisture deficit conditions in this study, may also be physiological, since it can neither be attributable to the climatic variables nor the soil moisture condition during the screening period. Although both early and late maturing sugarcane varieties have inherent capacity to tolerate drought, the early types usually showed superiority in sugar recovery than sugar yield/ unit area since such varieties tend to accumulate more dry matter following relief from moisture stress (Sudama, 1987). Clone F141 that is early maturing had the highest commercial cane sugar (%), which was significantly higher than those of other genotypes. Populations derived from the crosses were for most part superior to their parents for juice quality parameters especially %Polarimeter, indicating that juice quality could be highly heritable character. However, this juice quality parameter was generally low in the genotypes studied, which could be due to the adverse effect of drought at vegetative stage growth (Sudama, 1987). This condition inhibits sugar accumulation and deteriorates juice quality resulting from damage to apoplast cells that store sucrose in the parenchyma cells (Oworu et al., 1977; Adam et al., 1984). Therefore, there is possibility that these cells were destroyed during the prolonged drought stress at the vegetative stage in the susceptible varieties. Heterosis or hybrid vigour is manifested as an upward deviation of the F 1 hybrid from mid-parent value based on the average of the two parents (Johnson and Hutchinson, 1993) or better still, superiority of the F 1 over the better parent (David and Sally, 2005). Since high or low positive heterosis is often due to varying genetic composition between parents of different crosses for the component characters (Rajesh and Gulsan, 2001), the observed heterosis for some of the traits investigated under moisture deficit in the populations, emphasized the role of non-additive gene action particularly in the inheritance of cane yield and sucrose content in a vegetatively propagated crop like sugarcane. The preponderance of dominance variance for juice quality attributes and the significant mid-parent heterosis for these traits under moisture deficit attest to this. It also implies that the parents used in the hybridization programme differed significantly for genes governing tolerance to moisture deficit conditions which makes selection of superior progenies for major yield components under moisture deficit is feasible in sugarcane. Relative performance of genotypes in well-watered and moisture deficit conditions is a starting point in identification of traits related to drought tolerance as well as selection of genotypes for use in breeding for diverse environments. Progenies of crosses KD-01 x F141 and KD-01 x Co331 which demonstrated superiority for cane yield and sucrose content in well-watered and moisture deficit are better candidates in drought tolerant selection programme and so could be regarded as proven crosses that could be repeated in subsequent hybridization programme. Similarly, KD-01 is a male fertile clone, which could also be used in subsequent crosses with other female clones in the development of superior varieties for well watered and drought-prone environments of Nigeria. References Abayomi YA, Mobolaji MO (1995). Germination response of six sugarcane genotypes to osmotically-induced water stress. Bangladesh Journal of Sugarcane 17: Adam DG, McDavid CR, Wilson LR (1984). Sucrose storage in cells invitro a possible selection tool in sugarcane. Trop. Agric. 61: Clarke JM, Ronald MD, Towley-Smith TF (1992). Evaluation of methods for quantification of drought tolerance in wheat. Crop Sci. 32: David SB, Sally LN (2005). Beef cattle Handbook. BCH1400 pp Hallauer, A.R. and J.B. Miranda Fo (1984). Quantitative Genetics in Maize Breeding 2 nd Ed. IOWA State University Press, Ames, pp Ishaq MN (2005). Genetics and mechanisms of drought resistance in sugarcane (Saccharum officinarum L.) Unpublished Ph D thesis. University of Ilorin, Nigeria. Ishaq MN, Olaoye G (2006). Estimate of variance components and heritability in sugarcane under moisture stressed and non-moisture stressed conditions. Nigerian J. Genetics 20: Ishaq MN, Olaoye G, Akinsanya TO (2008). Screening sugarcane germplasm for drought tolerance in Nigeria. Plant Genetic Resources Newsletter. No. 154: Johnson HW, Hutchinson EH (1993). Absence of strong heterosiis for life span and other life history traits in Caenorhabditis elegans. Genetics 134: Moore PH (1987). Physiological basis for varietal improvement in sugarcane. in. Proc. of Int. Symp. on Sugarcane Varietal Improvement held at Sugarcane Breeding Institute, Coimbatore, India, 3-7. Sept pg Olaoye G (1999). Developing drought tolerant crop varieties for the savanna agro-ecologies of Nigeria. Pp in. G. Olaoye and D.O. Ladipo (eds.) Genetics and Food Security in Nigeria in the 21 st Century. A commemorative publication of the Genetics Society of Nigeria. Olaoye G (2001). Genetic variability between and within progenies of sugarcane crosses developed by modified polycross method at seedling selection stage. Ghana Journal of Agricultural Sciences 34: Olaoye G (2005). Estimate of ratooning ability in sugarcane under conditions of low available soil moisture in a savanna ecology of Nigeria. Moor Journal of Agriculture 6 (1) :16-23 Olaoye G (2006). Yield potential of non-irrigated sugarcane germplasm accessions in Savanna ecology of Nigeria. Moor Journal of Agriculture 7 (2):69-75 Oworu OO, McDavid CR, Macoll D (1977). Comparison of rates of storage of sucrose in eight clones of sugarcane as measured by sucrose uptake invitro. Ann. Bot. 41: Parsons LR (1979). Plant response to water stress. in. Christiansen, M.N. and Lewis,C.F. (Eds.). Breeding for favourable environments. New York. Pp Richards RA (1989). Breeding for drought resistance: physiological approaches. in. Baker, F.W.G. (Ed.). Drought resistance in cereals. Pp Rajesh K, Gulsan (2001). Expression of heterosiis in hot pepper Capsicum annum and eggplant. News letter 20:38-41.

8 Sugar Tech (2009) 11(4) : Sudama S (1987). Physiological basis for varietal improvement under stress environment in sugarcane. in. Proc. of Int. Symp. on Sugarcane Varietal Improvement held at Sugarcane Breeding Institute, Coimbatore, India, 3-7. Sept pg Steel RGD, Torrie JH (1980). Principles and Procedures of Statistics. A Biometrical Approach. 2 nd Edition. Mc Graw Hill Book Inc, New York.580pp. van Dilewjin C (1952). Botany of sugarcane Waltham, Mass. USA 371pp. Verma PS, Dhaka RPS, Singh HN, Singh SB (1987). Combining ability in sugarcane. Sugarcane 47(2): Wiedenfeld RP (2000). Water stress during the different sugarcane growth periods on yield and response to N-fertilization. Agric. Water Mgt. 43: ATTENTION Authors are required to submit, with their manuscripts, the names and full contact details (including address) of 3 potential referees in the specified area of research (who should not come from the same institute/city).