Identification of novel sources of genetic variation for the improvement of cold germination ability in upland cotton (Gossypium hirsutum)

Abstract

Upland cotton (Gossypium hirsutum) is inherently susceptible to low temperature stress especially during the early seedling growth and boll maturation stages. The goal of the study is to identify novel sources of genetic variation that can be used to improve cold tolerance of cotton during seed germination. Genetic diversity analysis of thirty accessions from the core Gossypium Diversity Reference Set (GDRS) and twenty recombinant inbred lines derived from intercrossing cotton mutants with altered fatty acid content profiles established genetic variation in the test germplasm based on simple sequence repeat (SSR) genotyping. The mutants clustered in a single clade, whereas the GDRS accessions were separated into four different clades. Screening for germination ability at 12°C and 15°C showed that the fatty acid mutants had a significantly better overall germination compared to the GDRS accessions. Hydropriming improved the germination rate and uniformity of the GDRS accessions at 12°C and 15°C but not those of the fatty acid mutants, which recorded a better overall germination at 15°C even without hydropriming. The tolerance of the FA mutants to cold stress during germination is proposed to be conferred by the higher proportion of unsaturated to saturated fatty acids in the mutants compared to the GDRS accessions. Principal component analysis established phenotypic patterns of variation that is consistent with the observed genotypic variation in the test germplasm. Results of the study indicate the potential of the mutants and select GDRS accessions as donors in breeding for cold germination ability.

Weathering the Cold: Modifying Membrane and Storage Fatty Acid Composition of Seeds to Improve Cold Germination Ability in Upland Cotton (Gossypium hirsutum L.)

“…Despite this fact, cotton remains sensitive to chilling temperatures, indicating a critical threshold for fatty acid unsaturation that will allow uniform germination of cotton seeds under low temperature. Recent studies showing the ability of FA mutants with increased fatty acid unsaturation to achieve more than 90% germination under cold conditions [67] supports this hypothesis. Results of phospholipidomic studies in corn also suggest that cold germination ability can be enhanced with modifications in fatty acid composition of seed oils toward higher levels of unsaturation [49].…”

“…To this end, screening of genetically diverse germplasm for potential sources of higher lipid unsaturation in seeds is extremely important. Results of recent studies conducted in our laboratory showed the faster and more uniform germination of ethylmethanesulfonate (EMS)-induced mutants of cotton with higher linoleic acid (52-63%) and lower palmitic acid contents (17-20%) compared to natural (i.e., non-mutated) accessions from the Gossypium Diversity Reference Set (GDRS) [66,67]. The mean average germination rate for the fatty acid (FA) mutants at 15 • C was almost 95%, whereas that of the GDRS accessions was only 36%.…”

Finding Needles in a Haystack: Using Geo-References to Enhance the Selection and Utilization of Landraces in Breeding for Climate-Resilient Cultivars of Upland Cotton (Gossypium hirsutum L.)

“…Similar results were obtained from genotyping 416 accessions of varieties, wild relatives and landraces of cotton from the Chinese collection using an 80K SNP array [ 31 ]. Aside from its rich genetic diversity, landraces have also been reported to harbor novel and beneficial alleles that can be used to enhance the adaptability of cotton to various environmental pressures [ 31 , 32 , 33 , 34 , 35 ]. Research to find novel sources of genetic variation that can enhance the ability of cotton to germinate under cold conditions not only established the genetic divergence of landraces from cultivated accessions of G. hirsutum but also demonstrated their potential to germinate even under critically low temperature [ 32 ].…”

“…Aside from its rich genetic diversity, landraces have also been reported to harbor novel and beneficial alleles that can be used to enhance the adaptability of cotton to various environmental pressures [ 31 , 32 , 33 , 34 , 35 ]. Research to find novel sources of genetic variation that can enhance the ability of cotton to germinate under cold conditions not only established the genetic divergence of landraces from cultivated accessions of G. hirsutum but also demonstrated their potential to germinate even under critically low temperature [ 32 ]. A separate study demonstrated the better osmotic adjustment ability of landraces under drought stress compared to cultivated cotton [ 33 ].…”

“…Amidst the burgeoning threats to cotton production, there is a growing interest in identifying new sources of genetic variation that can be used to enhance the adaptability of the crop to marginal environments. Panels of mutant lines and obsolete cotton varieties have been evaluated for their physiological responses to a multitude of environmental challenges including cold and drought stress but not the landraces [ 32 , 34 , 35 ].…”