Assessment of Drought Tolerance, Earliness and Grain Yield in South Sudan Sorghum Germplasm and Icrisat Lines

Abstract

Sorghum production is highly constrained by drought stress in semi-arid tropics leading to grain deficit, higher consumer food-commodity prices, food insecurity and malnutrition. The goal of the current study was to identify sorghum genotypes exhibiting genes for earliness and yield under drought stress conditions that could be utilized in the development of superior sorghum synthetics for improved food and nutritional security in drought prone areas of South Sudan. This study used sorghum germplasm comprising 47 genotypes from South Sudan collection and 34 elite lines drawn from ICRISAT-Nairobi‟s sorghum germplasm repository. The trails were laid out in a 9 x 9 alpha square lattice in a well irrigated and non-irrigated conditions Genotypes and water regimes had effects on days to flowering, staygreen scores, dry leaf scores, waxy bloom, leaf area, leaf rolling, total leaf count and lodging implying genetic diversity for the sorghum genotypes evaluated in this study. The superior lines that outperformed the check variety (Kiboko local2) for earliness were Wote collection1 (56 days), IESV 23010 DL (58 days), ZSV3 (60 days), Bizany (61 days) and Tabat (61 days). However, there were yield penalties recorded among the accessions wote collection1, Bizany, ZSV3 and Tabat. Thus, the accessions IESV 23010 DL would best serve as an ideal drought evading candidate with better performance for grain yield. The sorghum genotype Olerere (12.82%) exhibited staygreen trait while Omuhathi (76.23%) showed the highest senescence. Reduced total leaf counts and net leaf area were observed among improved drought tolerant lines namely IESV 92028 DL IESV 91111 DL, Mahube, IESV 92172 DL, Gwada and IESV 23010 DL. The accessions that scored dense wax load under drought stress condition were Gwada, ICSR 161, Mahube, AG8, IESV 91131 DL, IESV 91111 DL, IESV 92028 DL and IESV 92172 DL and comprised of inbred lines drawn from

ICRISAT- Nairobi gene bank. The genotypes Lobuheti (50.65g), IESV 91131 DL (46.52g), Lodoka1 (47.08g) and IESV 92172 DL (46.69g) showed superior field weights as opposed to the check variety (Kiboko local1). Accession IESV 91131 DL and IESV 92172 DL recorded high harvest index (3.13% and 6.86%) and threshing percentage of 73.94% and 67.34%. Results of correlation analysis revealed that panicle weight showed positive correlation with grain yield, harvest index, and panicle width suggesting that these traits could be used as the basis for indirect selection for high grain yield in sorghum breeding programs. There were significant differences among the maternal and non-maternal effects implying that maternal genes play a greater role in regulating maturity. There were higher predictability ratios for days to flowering, panicle weight and grain weight suggesting that additive genes play a bigger role than non-additive genes in conferring such traits. Negative significant general combining ability effects (GCA) were noted for days to flowering for parents ICSV 111 IN, B35 and Macia suggesting that these parents can be utilized as donor parents when introgressing earliness triat. The parental lines Lodoka, Okabir and Akuorachot with positive days to flowering implied lateness thus conferring the late physiological maturity. The study identified parental lines, Macia and ICSV 111 IN as exhibiting positive and high GCA effects indicating that they are good combiners for grain yield compared to parental lines B35, Okabir and Akuorachot which showed inferiority with regards to grain weight. Parental lines Macia and ICSV 111 IN also showed positive GCA for 100-seed weight, suggesting that they are good combiners for this trait and would therefore serve as good parental lines for the development of commercial synthetics.