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Genetic analysis and gain from selection of thrips resistance in cotton

Author:
Wann, Dylan Q., Dever, Jane K., Arnold, Mark D., Elkins, Heather D.
Source:
Euphytica 2017 v.213 no.3 pp. 70
ISSN:
0014-2336
Subject:
cotton, genes, genetic analysis, heritability, host plants, introgression, leaf area, models, phenotype, plant breeders, plant breeding, seedlings, selection intensity, Texas
Abstract:
Host plant resistance, in integrated systems, could be a critical tool for reducing thrips damage to seedling cotton. Plant breeders, however, need information regarding the genetic nature of resistance for effective and efficient introgression into breeding material. Trials were conducted in 2011–2014 at the Texas A&M AgriLife Research and Extension Center at Lubbock to elucidate the genetic nature of thrips resistance and the gains to be expected from visual phenotypic selection. Another objective was to validate a visual rating system for assessing thrips feeding injury in seedling cotton. Broad sense heritability (H ²) ranged 41–67%, depending on the family. H ² was higher in families with a day-neutral resistant parent than those with a photoperiodic resistant parent. Observed segregation ratios fit 3:1, 13:3, and 11:5 expected resistant/susceptible ratios, although nearly all of the phenotypic distributions exhibited closer fits to two-gene models. Additionally, the visual rating scale utilized in these evaluations exhibited a strong correlation (r ₛ = 0.884) with directly-quantifiable leaf area reduction data. These results suggest that thrips resistance is a dominant trait, under a high level of genetic control. There also appears to be at least a second gene (Thr2) aiding in genetic control of resistance. Actual gain from selection ranged 2–21% per cycle of selection, depending on the selection intensity. Optimum selection intensity in these evaluations was 5%, resulting in an approximate 21% gain. These evaluations revealed that host plant thrips resistance varies widely in cotton and can be sufficiently captured and advanced by plant breeders using visual selection.
Agid:
5757328