Genetic Gain in Yield and Changes in Agronomic Traits in Rice Cultivars (Oryza sativa L.) for Irrigated Ecosystem of North-Western Plain Zone of India

Punjab, traditionally was not a rice growing state, but has made tremendous progress in rice productivity and production since the introduction of semi-dwarf varieties in mid-sixties. There has been about 45-fold increase in production and more than four-fold increase in productivity over the years. Punjab Agricultural University (PAU), Ludhiana has been releasing rice varieties with improved productivity, better milling quality and disease resistance from time to time. Rice breeding programme at PAU is re-oriented keeping in view the farmer-consumer perspective and socio-economic concerns. Presently, the major focus is on breeding short-duration varieties. The earlier grown rice varieties had long duration of 160 days and yielded on average 7.5 to 8.0 tons per ha, producing 45-50 kg per day and consuming lot of water. The newly released rice varieties possess higher per day productivity thereby, yielding more per unit area per unit time and per unit of inputs/resources which will benefit the farmers as well as agro-ecosystem. The per-day productivity has increased significantly from 44.83 to 60.97 kg over the years (~36 %). The average increase in per-day productivity for every new variety is 1.8 kg. The yield data from multi-location trials of fifteen years from different maturity groups (long, medium and early) was analyzed to estimate genetic gain for non-Basmati rice in Punjab. Regression analysis was done by regressing the mean of top three genotypes, check means and experimental means on years. The top 3 genotpyes mean was significantly better than the checks and experimental means. The genetic gain showed non-significant increase or nearly static rice yields in genotypes. But for the gain in grain yields, genetic progress has been remarkable in breeding lines generated and tested in terms of enhanced tolerance to abiotic and biotic stresses, per day productivity and grain quality. Genetic gain should not be visualized only for increase in grain yield but with a much wider perspective including economic returns based on market value of produce, improved per day productivity, better resource use efficiency and stress tolerance ability, all of which require concerted breeding efforts leading to sustainability of the cropping system.