Improved Upland Cotton Germplasm for Multiple Fiber Traits Mediated by Transferring and Pyramiding Novel Alleles From Ethyl Methanesulfonate-Generated Mutant Lines Into Elite Genotypes.

Ethyl methanesulfonate (EMS) mutagenesis offers important advantages for improving crops, such as cotton, with limited diversity in elite gene pools. EMS-induced point mutations are less frequently associated with deleterious traits than alleles from wild or exotic germplasm. From 157 mutant lines that have significantly improved fiber properties, we focused on nine mutant lines here. A total of eight populations were developed by crossing mutant lines in different combinations into GA230 (GA2004230) background. Multiple lines in each population were significantly improved for the fiber trait that distinguished the donor parent(s), demonstrating that an elite breeding line (GA230) could be improved for fiber qualities using the mutant lines. Genotypes improved for multiple fiber traits of interest suggesting that allele pyramiding is possible. Compared to midparent values, individual progeny in the population conferred fiber quality improvements of as much as 31.7% (in population O) for micronaire (MIC), 16.1% (in population P) for length, 22.4% (in population K) for strength, 4.1% (in population Q) for uniformity, 45.8% (in population N) for elongation, and 13.9% (in population O) for lint percentage (lint%). While further testing for stability of the phenotype and estimation of yield potential is necessary, mutation breeding shows promise as an approach to reduce the problem of the genetic bottleneck of upland cotton. The populations developed here may also contribute to identifying candidate genes and causal mutations for fiber quality improvement.

Genetic diversity assessment of Georgia peanut cultivars developed during ninety years of breeding.

The cultivated peanut(Arachis hypogaea L.) has experienced severe genetic bottlenecks over the course of its evolution and domestication. Most genetic diversity studies in peanut have focused on global genetic stocks, wild accessions, and related species, but few have focused on elite cultivars. The objective of this project was to assess the genetic diversity of 32 peanut cultivars developed by the University of Georgia breeding program since its inception in 1931. Quantifying genetic similarity (GSIM) among these cultivars will provide a better understanding of their relationships and aid in breeding for cultivar development. Genotyping-by-sequencing (GBS), in concert with the recently published A. hypogaea genome sequence, was used to identify a total of 27,142 single nucleotide polymorphisms (SNPs) among these cultivars. Coefficients of parentage (CoP) were calculated based on publicly available pedigree information and compared with SNP-based GSIM estimates; the resulting correlations were low, ranging from R2 = 0.212-0.279. Although genetic diversity is generally low in cultivated peanut, our data indicate that the genetic diversity of Georgia cultivars has actually increased since the early days of the breeding program, likely a result of the incorporation of diverse germplasm and breeding lines into the program. The results reported here provide a valuable understanding of genetic variation among elite Georgia peanut cultivars that have had a significant impact on the peanut industry within the United States.