Electronic Journal of Plant Breeding, 9 (1) : 190 - 198 (Mar 2018) ISSN 0975-928X 190 DOI: 10.5958/0975-928X.2018.00023.6 Research Article Studies on genetic variability parameters and character association in bread wheat (Triticum aestivum L.) under timely and late sown environments of irrigated condition Khairnar S S, Bagwan J H, Yashavantha kumar K J*, Baviskar V S, Honrao B K, Surve V D, Khade V M, Chavan A M and Bankar B N Genetics and Plant Breeding Group, Agharkar Research Institute, Agarkar Road, Pune - 411 004, India E-mail: yashavantha@aripune.org (Received: 1 Jan 2018; Revised: 3 Feb 2018; Accepted: 3 Feb 2018) Abstract Sixteen diverse bread wheat genotypes studied at Agharkar Research Institute, Pune (Hol Farm) during rabi season of 2016-17. The present study revealed that the mean sum of squares due to genotypes was recorded significant for all the traits studied except grain yield per plot and harvest index in timely and late sown condition. The treatment versus genotype found significant among the traits days to heading and biomass per plot. The estimates of GCV, PCV, heritability and genetic advance were high to moderate in both conditions for the days to heading, productive tillers per meter, TGW, grain per spike, grain weight per spike, biomass per plot and grain yield per plot. Correlation coefficient reveled that, biomass per plot, productive tiller per meter, days to maturity gave the positive association with grain yield per plot in both the environments. One genotype was tolerant to grain yield per plot viz., HD 3219 (TS = 1052, LS = 934) under timely sown and late sown environments. It has been found that wheat genotypes differ their ability to respond to heat, there by tolerance, which could be useful as a genetic stock to develop wheat tolerant genotypes in wheat. Keywords Bread wheat, heritability, genetic advance, association Introduction Bread wheat (Triticum aestivum L.) is an important rabi season crop of India and Maharashtra with 30.23 m ha and 6.29 lakh ha, of area under wheat cultivation respectively. Productivity of Maharashtra recorded 12.05 q/ha and 30.93 q/ha of India (Anon., 2016). Wheat is an important cereal grain for export and domestic consumption in many countries throughout the world. Thus, continuous supply of wheat to exponentially increasing population is a major concern. The modern wheat breeding programmes focus on the improvement of agronomic and grain quality traits. The manipulation of wheat genetics has led to ever-increasing gains in yield and grain quality, while decreasing the ability of wheat to survive in the wild or varying climate especially with adverse condition. The ultimate aim of plant breeding programme is to develop cultivars with high potential and consistent performance over diverse environments. Wheat crop is sensitive to different abiotic stresses at almost all growth stages. The optimum range of temperature for growth stages is 18-24 0 C. Temperature beyond this range even for short period of 5-6 days causes 20% or more yield losses in wheat (Stone and Nicolas, 1994). Thermal stress due to rising ambient temperature during grain growth is one of the major constraints in enhancing wheat productivity particularly when the crop is sown late because of delayed harvesting of previous crops. Recently climate change has increased the risks of exposure to higher temperature by manifold even for timely sown wheat. Each degree rise in temperature causes 3-4% reduction in grain weight as reveled by studies under controlled and natural environments. The total wheat production in the country may get reduced at least 4 million tones any given year for each degree rise in ambient temperature. In general, the reduction in grain yield due to late sowing ranges from 25-35% depending on extent of delay and climatic conditions. In 2002-03, due to sudden increase in temperature during grain development stage, there was 9% reduction in total wheat production in India (Tiwari et al., 2014). The heat stress tolerance in wheat research, at natural field condition is mostly studied by the comparative analysis of timely and late sown condition with the facilitation of either regular irrigation or restricted irrigation. Late sown irrigated (sowing after 1 st December) wheat crop expose to high temperature