Gamma irradiation–induced variation in grain protein content and days from sowing to heading in M₅ mutant lines of spring wheat (cv. Eritrospermum-35)

Abstract

Bread wheat (Triticum aestivum L.) is a major staple crop providing essential calories for human diets. However, intensive breeding for yield has reduced genetic diversity for quality traits, including grain protein content (GPC). Induced mutagenesis offers an effective strategy to broaden the genetic base and generate novel alleles affecting agronomic traits. In this study, M₅ mutant lines of the spring wheat cultivar Eritrospermum-35 were developed through gamma irradiation at 100 Gy and 200 Gy. Lines were evaluated for variation in GPC and days from sowing to heading under controlled greenhouse conditions. GPC was measured using near-infrared reflectance spectroscopy (NIR), and allelic variation at the candidate gene Eps-Am1 was analyzed using PCR-based markers. Substantial variation in GPC was observed. The 100 Gy lines showed GPC values ranging from 12.60% to 14.43% (mean 13.56 ± 0.57%), whereas the 200 Gy lines had a mean GPC of 13.76 ± 0.63%. Eleven mutant lines (37%) exhibited significantly higher GPC (5.7–11.0%) than the parent. Importantly, the increase in GPC was not associated with a reduction in thousand kernel weight; TKW values were higher in irradiated lines compared with the parent. Days to heading differed between treatments: 100 Gy lines headed earlier, while 200 Gy lines showed delayed heading. Molecular screening identified new alleles of Eps-A^m1, with allele carriers generally exhibiting earlier heading. Overall, gamma irradiation generated valuable genetic variation for improving grain protein content and adaptive traits in spring wheat.

Key words: gamma irradiation, grain protein content, days to heading, thousand kernel weight, spring wheat, Eps-A^m1, mutation breeding.