Identification of vegetative heat‐tolerant upland cotton (Gossypium hirsutum L.) germplasm utilizing chlorophyll fluorescence measurement during heat stress

Abstract

Heat stress adversely affects upland cotton (Gossypium hirsutum L.) production in the United States. Heat tolerance is difficult to determine, especially when yield and fibre quality are the parameters measured in photoperiodic, non-adapted genotypes. Our objective was to evaluate wild (mostly photoperiodic, non-adapted) genotypes for vegetative heat tolerance using chlorophyll fluorescence. Parameters were measured in three phases of heat stress assays to select candidate lines for introgression of increased heat tolerance into commercial cotton germplasm. Forty-four wild accessions were selected from 1762 wild accessions in the USDA germplasm collection using a single-leaf sample assay (phase I). In the growth chamber, 6-week-old cotton plants were subjected to heat stress at 45°C and 80% humidity for 24 h. After heat stress, the mean Φ PSII for the selected accessions was higher than that of a set of randomly chosen accessions and adapted cultivars (phase II). In the field under high temperatures (>35°C), the top nine accessions had higher average Φ PSII than adapted cultivars (phase III). Based on these results, the three-phased stepwise approach was consistent in identifying putative genetic resources for increased vegetative heat tolerance. Accessions were identified that may have potential as genetic materials for development of adapted heat-tolerant upland cotton germplasm.

Distribution and Differentiation of Wild, Feral, and Cultivated Populations of Perennial Upland Cotton (Gossypium hirsutum L.) in Mesoamerica and the Caribbean

“…The ecological niche where these wild cotton populations are encountered in Mesoamerica clearly indicates that they represent a great reservoir for genes and alleles related to tolerance to abiotic stresses (water, high temperature or saline stresses). Even though these wild cottons are excellent sources for widening the genetic base for breeding because of their complete interfertility with modern cultivars of G. hirsutum [86] , this type of material has so far been poorly characterized for its physiological and eco-physiological adaptive traits [87] , [88] and rarely exploited in breeding programs [89] , [90] .…”

Identification and Characterization of Contrasting Genotypes/Cultivars for Developing Heat Tolerance in Agricultural Crops: Current Status and Prospects

“…Chlorophyll fluorescence was used to screen cotton landraces-6-week-old cotton plants were subjected to heat stress at 45 • C in a growth chamber to determine thermotolerance in terms of photosynthetic ability, independent of agronomic yield and productivity. Three genotypes (TX2287, TX2285, and TX761) maintained high photosynthetic efficiency (F v /F m 0.57), relative to sensitive genotype (F v /F m 0.46) (Wu et al, 2014). In another growth chamber study, a commercial set of eight cotton genotypes was screened for heat tolerance by subjecting to heat stress (>35 • C); four genotypes (SG215BR, ST474, and DP444BG/RR) had relatively high F v /F m indicating that they suffered less from stress, while Sphinx and Acala Riata had low F v /F m , indicating temperature sensitivity (Bibi et al, 2004).…”

Genotyping-by-Sequencing of Gossypium hirsutum Races and Cultivars Uncovers Novel Patterns of Genetic Relationships and Domestication Footprints

“…All of these advantageous traits can be potentially applied to improve cotton yield and quality as well as tolerance to environmental stresses. 8,12-14…”