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.

Highlights

  • Upland cotton (Gossypium hirsutum) is native to tropical and subtropical environments and grows best under long-season cultivation in warm climates

  • While late season planting provides an optimum range of temperature for seed germination, it runs the danger of having the crop mature late in the fall when unexpected cold snaps below 15 °C are very likely to occur and negatively impact yield potential, as well as fiber and seed quality (Gipson et al 1969)

  • A subset of the core Gossypium Diversity Reference Set (GDRS) (Hinze et al 2015, 2017) composed of 30 G. hirsutum accessions from the National Cotton Germplasm Center, as well as 20 recombinant inbred lines (F5 generation) that were derived from intercrossing the fatty acid mutants AFIS 1-1422-A5 and SCM3-7-3-A3 in the genetic background of Acala 1517-99 and SC 9023, respectively, (Thompson et al 2019) were used in the study (Table 1)

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Summary

Introduction

Upland cotton (Gossypium hirsutum) is native to tropical and subtropical environments and grows best under long-season cultivation in warm climates. Decrease in temperature below 15 °C concomitantly reduces germination percentage and induces chilling injuries that often leads to seedling malformations, taproot loss, reduced vigor, increased occurrence of seedling diseases, poor stand establishment and reduced yields. While late season planting provides an optimum range of temperature for seed germination, it runs the danger of having the crop mature late in the fall when unexpected cold snaps below 15 °C are very likely to occur and negatively impact yield potential, as well as fiber and seed quality (Gipson et al 1969). Early season planting to ensure maturation of the crop under warmer temperatures risks poor germination, emergence and stand establishment due to cold stress in the early spring (Christiansen and Thomas 1969; Pettigrew 2002; Buxton et al 1977)

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