Mapping of Gene(s) Controlling Grain Yield and its Components in Bread Wheat Under Rainfed and Supplementary Irrigation Conditions using Molecular Markers

Water deficit stress is one of the most important abiotic stress reducing wheat yield world wise which affect its sustainable production. To map gene(s) controlling drought tolerance related traits in wheat, 142 recombinant inbred lines derived from a cross between Azar2 (drought tolerant) and 87zhong291 (high yielding) was evaluated under rainfed and supplementary irrigation conditions. The measured traits were grain yield, 1000 grain weight and number of spikelet per spike. Parental polymorphism was assessed using SSR and ISSR markers and 24 SSR marker and 16 ISSR polymorphic markers were used for analysis. Linkage analysis was performed to assign these markers to the population linkage map consisted of 45 SSR and AFLP markers. The linkage map span 1310 cM of wheat genome with 19.55 cM distance between two neighboring markers. Based on composite interval mapping, 10 and 18 QTLs were identified for grain yield, under rainfed and supplementary irrigation conditions, respectively. Under rainfed and supplementary irrigation, five and nine QTLs were mapped for number of spikelet per spike. For 1000 grain weight, four QTLs under rainfed condition and nine QTLs under supplementary irrigation were detected. Two and four QTLs detected for grain yield and 1000 grain weight, respectively, were stable under both conditions. For the studied traits, number of common QTLs were identified which could be due to gene linkage or pleiotropic gene effect. The common QTLs for grain yield and number of spikelet per spike (18.26%) as well as for grain yield, number spikelet per spike and 1000 grain weight on linkage group 2 and the common QTL for number spikelet per spike and 1000 grain weight on linkage group 3 with determining more 15% of these trait phenotypic variance were identified as major QTLs. Some of the markers were tightly linked to the QTLs which could be used for selection of drought tolerant lines.