Genetic diversity analysis among pre-green revolution, post-green revolution era cultivars, and wheat landraces as revealed by microsatellite markers

Abstract

Bread wheat (Triticum aestivum L.) is the most widely grown crop in the world, and India is the second largest wheat producer after China. Introduction of input-responsive, semi-dwarf varieties set the foundation for the green revolution in the mid-1960s. To meet the future challenge of increasing food production with a shrinking land base, new varieties with higher yield potential and increased yield stability have to be developed by using the diverse genetic resource. The objective of this study was to evaluate genetic diversity in 74 wheat genotypes including released varieties in India occupying the pre-green revolution period (before 1965) and post-green revolution period (after 1965) and land races with microsatellite markers. SSRs represent a powerful tool to quantify genetic diversity in wheat. In total, 170 alleles were detected with an average of 3.3 alleles per locus. Overall, 24 rare alleles were present and 11 unique alleles were found in the studied landraces only. A positive correlation was found between the number of alleles and genetic diversity. Genetic relationships as determined by UPGMA (NTSYS-pc) and structure analyses grouped all modern wheat cultivars under one node. The traditional tall varieties released during the pre-green revolution era were clustered along with some of the landraces, indicating that they had possibly been developed through selection among the landraces. Diversity among the released varieties in the post-green revolution era has widened rather than narrowing down. Molecular variance analysis showed that variance was mainly distributed within (91.9%) rather than among (8.01%) the bread wheat varieties and landraces. The diversity obtained within the landraces proves them to be an important reservoir of biodiversity and source of novel alleles for use in breeding programs. Landraces such as MPG 62 and MPG 82 can be used for introgressing rare and unique alleles in the genetic background of high-yielding varieties.