Selection of Tolerant Sorghum Varieties Grown in a Striga Infested Field for Future Breeding Purposes

Abstract

Sorghum is a crucial food security crop with outstanding potential to meet growing global demand for food at a time of uncertainty posed by climate change. Striga (Striga hermonthica) is an important parasitic weed in sorghum causing huge loses under heavy infestation. Fourteen sorghum lines were assessed for their response to Striga infection under field condition to select lines that seem tolerant to Striga infection for future breeding purposes. An introgression line, Asareca T1, tolerant to Striga and Tabat, susceptible to Striga were included as controls. The experiment was carried out in a Striga sick field at the Food Crop Improvement Centre, Kenya Agricultural and Livestock Research Organization (KARLO) experimental fields in Alupe, Busia County. It comprised of two nitrogen fertilizer levels: N0 (N_o nitrogen) and N₁ (90 kg N Ha^-1) laid out in a randomized complete block design with two replications. Application of fertilizer significantly reduced days to Striga emergency, Striga count, and days to maturity, while it increased plant height, grain yield, panicle length, and dry weight in Asareca T1, 2026, 2038, 2048, 2054, and 2060. Striga count was negatively correlated with plant height (r = -0.81, p < 0.05), grain yield (r = - 0.74, p < 0.05), dry weight (r = - 0.78, p < 0.05), days to Striga emergence (r = - 0.64, p < 0.05), and panicle length (r = - 0.74, p < 0.05) in Tabat, 2011, 2015, 2021, 2028 and 2030. Striga count was positively correlated to number of tillers (r = 0.66, p < 0.05) and days to maturity (r = 0.76, p < 0.05) in Tabat, 2028, 2015, 2006, 2011, 2012, and 2006. The application of optimum fertilizer 60 kg ha^-1 suppressed Striga emergence. It was also found that Tabat, 2006, 2011, 2012, 2015, 2021, 2028, and 2030 lines were susceptible to Striga attack based on the total number of Striga seedlings attached, which was more than six. Sorghum lines Asareca T1, 2026, 2029, 2038, 2040, 2048, 2054, and 2060 seem to be tolerant to Striga infectivity. Therefore, these lines have been selected for inclusion in future breeding programmes in selecting sorghum lines that are tolerant to Striga and that are preferred by farmers. Considerable efforts have been invested in breeding for Striga tolerance in sorghum and significant progress has been made in the development of improved selection methods.