The demand for wheat will be increased 60 % compared to existing by 2050 and the wheat productivity of Nepal is lower than world’s average productivity. Therefore, it is important to increase the yield potentiality of wheat. This research was conducted for the estimation of variability and association among yield and yield components of wheat. The experimental field was designed in alpha lattice design with 20 diverse wheat genotypes considering 12 important traits. In variability analysis, thousand kernel weight (TKW) had maximum values for the genotypic coefficient of variance (GCV) (11.83%) and phenotypic coefficient of variance (PCV) (12.14%) indicating the presence of high variation in TKW. The number of spikes/m2 (NSPM) and grain yield (GY) showed higher values for heritability (82.62% and 58.95%) and GA (73.36 and 456.25). These traits have additive gene action and are less affected by the environmental condition. Plant height (PH) had significant positive correlation with GY (0.346) and chlorophyll showed highly significant negative correlation with GY (-0.448). NSPM and PH had a maximum positive direct effect (0.375 and 0.347), chlorophyll content had maximum negative direct effect (-0.234) and days to heading (DTH) and days to anthesis (DTA) showed a positive indirect effect on GY. The selection of genotypes with higher values of PH and NSPM along with moderate or low chlorophyll content is a prerequisite for attaining a higher yield in wheat. Genotypes having longer DTH, DTA and days to maturity (DTM) should be considered during selection of genotypes to obtain higher yield.

Wheat is third most important food crop in Nepal after rice and maize. The productivity of wheat in Nepal is lower than world productivity. The causes behind it are drought and heat stresses, genotype, climate change, global warming lack of inputs and irrigation. Yield of wheat is quantitative trait which is adversely affected by environmental factors. Therefore, only genotypic selection is not effective and selection should be based on performance of yield components and morpho-physiological characters. Correlation coefficient analysis provides the direction and degree of relationship between yield attributing characters. Path coefficient analysis helps to analysis direct and indirect effect of one variable to another. It helps in partitioning direct and indirect causes of correlation. Among agronomic trait, days to booting, days to heading and days to maturity show negative correlation to grain yield but chlorophyll content, plant height, spike/m2, number of spikelet/spike, number of grain/spike, spike length, spike weight is directly correlate to grain yield .Spike weight, spike length, thousand kernel weight, and number of spike per meter square, number of grains per spike and days to anthesis has direct positive effect on grain yield and plant height, chlorophyll content and days to heading have negative direct effect on grain yield.

Correlation coefficient and path analysis were computed between yield and yield attributing trait among twenty genotypes of wheat. The research was conducted during winter season of 2020/2021 in the agronomic field of the Institute of Agriculture and Animal Science (IAAS), Bhairahawa, Nepal to identify the traits which influence the positive and negative relation to grain yield. Twenty genotypes of wheat were sown on 24th December 2020 on alpha lattice design with two replications. It has been found that under heat stress, DTB, DTH, DTM, CLC, PH, NGPS show a non-significant positive correlation with GY. Similarly ET shows a highly significant positive correlation to GY. However, SL, SW, TKW have a non-significant negative correlation with GY. In path analysis, DTM and ET have a positive direct effect on GY and DTH, SL, CLC and NGPS have an indirect effect on GY. Hence, the ET and DTM can be used to select wheat genotype for breeding purpose and studies to improve yield of genotypes under heat stress condition.

Wheat (Triticum aestivum) is the third most important cereal crop in Nepal after rice and maize. The research is carried out during the winter season in agronomic field of the Institute of Agriculture and Animal Science (IAAS), Bhairahawa, Nepal. Sowing is carried out 28th November 2020 and 24th December 2020 on alpha lattice design with two replication of twenty wheat genotype under normal and late sowing respectively. In the late sowing condition, all genotype's performance is reduced as compared to normal sowing. Under late sown condition, high temperatures reduced the days to booting (15.64%), days to heading (14.97%), days to maturity (14.16%), chlorophyll content (15.99%), plant height (8.59%), spike length (7.03%), number of spikelet per spike (9.21%), number of grain per spike (10.6%), spike weight (15.32%), effective tiller/m2 (9.92%), thousand kernel weight (10.3%) and grain yield (22.5%). NL 1420 presented higher 4118 kg/ha and 3310.5 kg/ha yield respectively and BL 4407 presented early maturity 119.2 DAS and 100.6 DAS respectively in normal sowing and late sowing condition. In a combined environment, maximum grain yield is recorded in NL1420. The result suggested that the tolerant line against the late sowing condition can be used as genetic resource for crop improvement and promote for grain yield.