Quantitative Genetics of Drought and Heat Tolerance in Nigerian Sorghum Landraces: QTL Mapping and Breeding Implications

This study conducts QTL mapping for drought and heat tolerance traits in Nigerian sorghum landraces, contributing original quantitative genetic knowledge that informs targeted breeding for climate change resilience. Nigerian sorghum landraces, particularly those from the semi-arid North West and North East zones, carry unique allelic variation for drought and heat tolerance that has been shaped by centuries of farmer selection under climate stress. Identifying the genomic regions underlying these adaptive traits is essential for efficient introgression of tolerance alleles into high-yielding backgrounds. This study develops a bi-parental mapping population of 250 F3 lines from crosses between a drought-tolerant northern Nigerian landrace from Borno State and a high-yielding but drought-susceptible improved line. The population is phenotyped for drought and heat stress indices including relative water content, chlorophyll fluorescence, canopy temperature, anthesis to silking interval under stress, and yield stability across four contrasting environments at Kano, Maiduguri, Ibadan, and IITA Kano research stations. Genotyping uses SNP arrays providing 45,000 genetic markers. QTL analysis uses composite interval mapping and multiple interval mapping. Findings reveal 14 significant QTL for drought-related traits, with three QTL on chromosomes 3, 6, and 9 collectively explaining 38 percent of variation in yield stability under drought. Two previously unreported QTL for canopy temperature are identified in the northern landrace. Major QTL co-localise with known stress response genes. The study contributes original Nigerian landrace QTL mapping data and recommends marker-assisted introgression of identified QTL into improved Nigerian sorghum varieties.

Keywords: QTL mapping, sorghum landraces, drought tolerance, Nigeria, quantitative genetics.