Genetic Gain and Traits Plasticity in Wheat Cultivars Developed for Irrigated Ecosystems of NWPZ of India From 1900 to 2016

Abstract

Knowledge about the yield gain over the years due to associated changes in the yield component traits is essential for a critical understanding of yield-limiting factors. To estimate genetic gain in grain yield of wheat varieties released between 1900 and 2016 for North-Western Plain Zone of India and to identify agronomic and/or genetic basis of the realized gains, two sets of wheat genotypes with 14 and 10 varieties in each comprising mega varieties and two recently developed genotypes were evaluated, under timely sown tilled and early sown conservation agriculture conditions respectively for 4 consecutive years. The average annual genetic gain in grain yield since 1905 under timely sown condition was found to be 0.544% yr-1 over the average of all varieties and 0.822% yr-1 (24.27 kg ha-1 yr-1) over the first released variety, NP4. The realised mean yield increased from 2950 kg ha-1 of the variety NP 4 released in 1905 to 5649 kg ha-1 of HD 3086 released in 2014. Linear regression analysis revealed a linear reduction in height and peduncle length over the breeding periods with a linear increase in biomass over the years at the rate of 43.9 kg ha-1 yr-1 or relatively at 0.368% yr-1 mainly because of linear increase in days to heading and crop duration. However, it showed no trend for tiller number and thousand kernel weight but an increase of 0.11 grains per spike yr-1 was evident from the study. The absolute and relative gain yr-1 for harvest index (HI) was found to be 0.0007% and 0.198%, however, polynomial regression shows hardly any improvement in HI since 1982. Interestingly, genetic gain evaluation under early sown conservation agriculture conditions for four years shows similar relative gain (0.544%) but higher absolute gain (29.28 ha-1 yr-1). Major mega varieties like Kalyan Sona, HD2009, PBW 343, HD2967 and HD3086, which occupied comparatively larger area proved to be highly plastic and able to respond well to the improvements in the production environment under timely sown conditions.