QTL mapping: insights into genomic regions governing component traits of yield under combined heat and drought stress in wheat

The experiment was carried out at ICAR-IARI, New Delhi (28.6550° N, 77.1888° E, MSL 228.61 m) over two consecutive crop seasons (2021-22 and 2022-23). The study involved the evaluation of RILs developed from GW322/KAUZ along with their parents under two distinct conditions: heat stress (late sown irrigation; LSIR) and combined drought and heat stress (late sown restricted irrigation; LSRI) in augmented design (Federer, 1956; Federer, 1961; Searle, 1965). The experimental field was divided into four blocks, with four checks utilized in the study. Each check was replicated three times. Phenotyping:The instrument GreenSeeker™ was used to record NDVI. NDVI was measured at four stages: at anthesis, 10 days after anthesis, 20 days after anthesis and 30 days after anthesis. To record TGW, manual counting of grains was followed and the weight of the grains was recorded in grams with an electronic balance. Days to heading is the number of days from sowing to 50% heading is recorded for each genotype. Plant height is measured from the base of the ground to the tip of the plants. It’s measured using a measuring scale and the unit of measurement is cm. Spike length is measured from the base to the tip of the spikelets excluding awns. It’s measured using a measuring scale and the unit of measurement is cm. 20 random spikes were harvested from each plot. The harvested spikes from each plot were threshed and cleaned separately. The weight of seeds from 20 spikes was recorded with an electronic balance. The weight of 20 spikes was divided by 20 to obtain individual spike weight and the unit of measurement is gm. After the crop attained harvest maturity the crop was cut to the base using a sickle and the weight of the entire biological yield was measured using a hand-held mechanical balance. The unit of measurement is kg. Spikes from each plot were threshed separately using a full man thresher and seeds were cleaned to remove chaffy material. The seed yield from each plot was measured using a mechanical balance. The unit of measurement is kg.