Breeding for earliness and thermo-tolerance in wheat suited to early, late and very late sowing in northwestern India

Abstract

Wheat varieties WR 544, HD2285, Sonalika, Halna, Raj3765 and PBW373 recommended for late sown conditions in India (i.e., on or after 25u, December) along with contrasting check HD2687 released for timely sown conditions (i.e., 1 to 15th November) and C306, a rainfed cultivar (last week of October and first week of November) were studied to know the genetic basis of flowering time. The date of flowering and maturitl were comparatively evaluated bl planting them on 2ot September, 15th November, 25t December and 15u, of January over a period of more than four years. The photoperiod insensitivity in these genotypes was determined by a Ppd-01 allele. Gene expression in response to vernalization was examined based on pedigree analysis. It was found that each of these genotypes carries Vrn-A1, Ppd-01 genes except late flowering genotypes, HD2687 and C306, which carried vrnA 1 and Ppd-01 alleles. The days to flowering of 20th September sown crop ranged from 44 to 56 (photo insensitive), except the cultivars HD2687 and C306 which flowered in 83 and 93 days and expressing their response to vernalization. WR544 demonstrated tremendous resilience with respect to flowering and other agronomical traits under 20u, September and 25th December sown crop since it flowered in 44 days and thus characterized as an ultra early flowering genotype. It involves spring wheat Sonora 64 in its pedigree originating from Mexico. Sharbati Sonora, a mutant of Sonora 64 has been identified to carry Vrn-A 1 and Ppd-01 alleles. Similarly Raj3765 and Halna involved Ciano and Sonora 64 in their parentage both carrying Vrn-A 1 and Ppd-01 alleles making these cultivars as photo insensitive. It can therefore, be conclusively said that both the alleles Vrn-A 1 and Ppd-01 have been introduced in Indian genotypes from Mexican germplasm. The combined average yield of WR544 and Raj 3765 sown on 20th September (early sown, autumn) and 25u, December (late sown, winter) over two seasons was 70.2 and 62.8 q/ ha respectively. This indicated that the crop sown in September can be harvested in the month of December leaving enough time for preparation and raising subsequent wheat crop on the same piece of land. Since WR544 out yielded all the varieties tested, it can therefore be popularized for early autumn and late sewings.