GENETIC VARIABILITY FOR SPROUTING ABILITY AND ESTABLISHMENT OF CASSAVA (Manihot esculenta Crantz) IN THE NIGERIAN SAVANNA.

GENETIC VARIABILITY FOR SPROUTING ABILITY AND ESTABLISHMENT OF CASSAVA (Manihot esculenta Crantz) IN THE NIGERIAN SAVANNA.

Abstract:

The studies were carried out to estimate the extent of genetic variability and character relations in cassava (Manihot esculenta Crantz) for sprouting and establishment ability. Forty cassava clones comprising: 33 Nigerian cassava land races and 7 IITA improved clones were selected for the study based on their popularity in the 36 states of Nigeria. The analysis of variance for sprouting ability, establishment ability, cutting characteristics, growth parameters, cassava mosaic disease (CMD) and cassava bacterial blight (CBB) showed highly significant differences (p=0.01) among the genotypes. Combined analysis of variance for sprouting ability, establishment ability, growth parameters,(no of shoots per plot, number of roots per plot, fresh weight of shoot, fresh weight of root, dry weight of shoot, dry weight of root, plant height), CMD and CBB revealed highly significant effects of clones, environments and their interactions (G x E). Locations also differed significantly. Highly significant G x E interactions were observed for all the traits measured. The estimates of genetic variances obtained in this study were comparable among the locations. However kuru location had lower estimates than the other locations. The genotypic coefficients of variation (GCV) were lower than the phenotypic coefficients of variation (PCV) in all the characters studied thus indicating considerable influence of environment on the expression of these characters. The high GCV values for the characters revealed that the range of variability in the population was large thus suggesting that there is scope for further improvement of these traits through selection. The genetic variances obtained were positive for all the traits studied. Significant genetic differences existed for all the traits studied and varied widely among locations. From the results, most cassava clones achieved their maximum sprouting potential between 21 and 28 days after planting. Among all the locations, Samaru had the overall best mean performance and Kuru location had the lowest mean performance. The TMS 30572 had the overall best mean performance across the four locations for sprouting and establishment ability. Antiota, TMS 91934, 82/00661, 82/0058, Odungbo, Abachaji, and Oyarugba had mean performance of above 90% sprouting ability and were among the best clones selected for high sprouting ability and establishment potentials. The studies also showed that evaluating for sprouting and supplying should be done between 21 and 28 days after planting. The forty cassava clones that were involved in the studies showed varying levels of susceptibility to cassava mosaic disease and cassava bacterial blight. Amala, Atu Iwo, Bagi Wawa, Oko Iywo, Olekanga, 2nd Agric were the most resistant clones in the population for CMD, while TMS 81/00110, TMS 82/00058 and TMS 30572 were the resistant clones to CBB. Correlation coefficients in all the four locations between phenotypic and genotypic correlation showed similar trend and magnitude. Genotypic coefficients of correlation were higher than their corresponding phenotypic correlation coefficients. Highly significant positive genotypic and phenotypic correlation coefficients were observed between sprouting and establishment. Stake fresh weight, stake girth, stake volume, stake bulk density, had significant positive genotypic and phenotypic correlation with sprouting and establishment. Number of shoot, number of roots, fresh weight of shoot, fresh weight of root, dry weight of shoot, dry weight of root and plant height were positively correlated with sprouting and establishment. However, sprouting and establishment correlated significantly, but negatively with number of nodes and pith wood ratio implying that increasing number of nodes of cuttings and pith wood ratio would result in decrease of the sprouting ability of the different genotypes. Similarly, the significant negative correlation between sprouting ability and establishment and pith wood ratio indicated that increasing pith-wood ratio would also result in decrease of the wood portion of the stakes thus reducing the food reserve in the wood and consequently resulting to poor sprouting and establishment. Significant but negative phenotypic correlations were observed between sprouting, establishment and CMD and CBB recorded at 3 months after planting. The implication of this observation for breeding could mean that selections aimed at increasing sprouting and establishment abilities would probably lead to decreased pith-wood ratio, decreased CMD, decreased CBB and decreased number of nodes, thus these characters could therefore be improved simultaneously.

GENETIC VARIABILITY FOR SPROUTING ABILITY AND ESTABLISHMENT OF CASSAVA (Manihot esculenta Crantz) IN THE NIGERIAN SAVANNA.

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