Development and molecular marker characterization of a backcross derived wheat population for genetic analysis of drought tolerance

A backcross derived population was developed using HD 2967 as recurrent parent and Excalibur as donor parent. A population consisting of 210 BC2F4 lines was developed. These lines were evaluated for drought stress related traits and drought stress qtl linked molecular marker based characterization. Analysis of variance showed significant difference between population lines for various morphological and physiological traits. Genotypes D-61, D-2, D-127, D-30, D-74, D-121, D-73 and D-90 performed best on basis of averaged yield performance under rainfed environment. Genotypes D-61, D-73, D-90, D-30, D-74 and D-121 showed stability under stress environment. D-2 and D-127 performed well under rainfed environment but showed reduction in yield under irrigated conditions. Genotypes D-111, D-142, D-61, D-86, D-97 D-140, D-147 and D-90 showed maximum yield under irrigated environment. Genotypes D111, D-142, D-86, D-97 D-140 and D-147 showed significant yield reduction under rainfed environment. Correlations were calculated for traits. At site 1 under rainfed environment grain yield showed negative correlation with days to anthesis (-0.467), NDVI at anthesis (-0.375), NDVI at grain filling (-0.352), chlorophyll content at grain filling (0.230), flag leaf length (-0.310), tillers per meter (-0.146) and spikelets per spike (-0.263). Under irrigated environment at site 1, grain yield per plot showed negative correlation with days to anthesis (-0.252), NDVI at anthesis (-0.177), NDVI at grain filling (-0.289), chlorophyll content at grain filling (-0.223), spike length (-0.208) and spikelets per spike (-0.240). At site 2 (NA) under rainfed environment grain yield showed negative correlation with days to anthesis (-0. 619), NDVI at anthesis (-0.475), NDVI at grain filling (-0.358), chlorophyll content at grain filling (-0.241), tillers per meter (-0.287) and spikelets per spike (-0.287). Under irrigated environment at site 2, grain yield showed negative correlation with days to anthesis (-0.566), NDVI at grain filling (-0.466), chlorophyll content at grain filling (-0.145), flag leaf length (-0.157), spike length (-0.134) and spikelets per spike (-0.325). Traits showing negative correlation with yield showed positive correlation among themselves. Canopy temperature at grain filling showed positive correlation with yield at both the sites under both environments. Traits generally associated with tolerance gave negative correlation with yield under stress as well as non stress conditions on account of exceptional cool and moist weather pattern during the 2014-15 crop season. Backcross derived population was screened for root shoot traits using cigar roll method. Analysis of variance showed significant differences between 210 progenies for root length, shoot length and root to shoot ratio indicating segregation for these traits in progenies. D-55, D-57, D-210, D-99, D-90, D208, D-91, D-93 and D 96 were best genotypes for root shoot traits. Seven SSR markers linked with drought stress related qtl were used for population survey. Markers barc 137 showed association with yield, NDVI, chlorophyll content and days to anthesis. Marker barc 137 showed percent variation explained (PVE) ranging from 10.64 % to 12.47 % for days to anthesis. This marker showed significant association with days to anthesis at both sites (site1 and site 2) and under both environments. For yield barc 137 explained PVE ranging from 6.19 % to 11.36 %. PVE explained by marker barc 137 ranged from 7.68% to 9.52% for NDVI at anthesis. PVE explained by marker barc 137 for NDVI at grain filling ranged from 7.26 % to 8.80 %. Marker gwm 344 was associated with plant height at site 2 under rainfed environment (PVE 5.96 %) and chlorophyll content at grain filling under irrigated environment at site 1 (PVE 6.90 %). Drought stress related qtl markers showing association with various drought stress related traits and explaining greater than 10 % PVE were identified indicating mapped qtl showed significant contribution for improving drought stress traits under our environment. For improving emasculation methodology for wheat X maize system of DH production various emasculation techniques were compared. Hot water treatment method resulted in high embryo formation frequency (30.88%). Percentage of selfed seed setting was low (3.20%) indicating efficacy of this method. Intact glume method resulted in high embryo formation frequency (24.35%). Cut glume emasculation method resulted in decrease embryo formation frequency (10.92%). Plastic bag emasculation resulted in decrease in number of caryopses formed owing to large percentage of selfed seed setting (32.99%). Embryo formation frequency was high (23.54%).