Upland cotton (Gossypium hirsutum L.) is the world’s most important fiber crop. The U.S. is the third largest cotton producer after India and China and the largest cotton exporter in the world. However, cotton is grown in arid and semi-arid regions where thrips (Frankliniella occidentalis) and Verticillium wilt (VW, caused by Verticillium dahliae) are important challenges in Upland cotton production in the U.S., because most cotton cultivars and breeding lines are susceptible to both pests due to their selections under optimum non-stress conditions. Also, adding economic values to cottonseeds such as breeding for glandless cotton is becoming an important goal in cotton breeding. But the response of glandless cotton to biotic stresses should be examined. Therefore, the objectives of this study were, to evaluate new glandless cotton lines for thrips and VW resistances, to perform comparative analysis between glanded and glandless cotton, and to identify the most promising glandless lines that can be used in cotton breeding to develop resistant cotton cultivars to biotic stresses.
In the first study, 210 Upland cotton lines including selections from a hybrid between glanded check cultivar Acala 1517-08 and glandless check cultivar Acala GLS were separated into seven independent replicated tests designated as (trials S, T, U, V, W, FT, and FV) to study their response to thrips resistance. Results showed that significant genotypic differences were detected for trial FV at P < 0.05 and trials T and W at P < 0.1. Although many glandless lines exhibited lower thrips rating scores than the glanded check Acala 1517-08, lines SA 2248 and SA 2455 (in trial T), and MBC 7570 (in trial W) were significantly lower than Acala 1517-08. Greenhouse tests showed higher thrips rating scores of 2.97, 3.16, and 3.04 than the field conditions (1.48, 1.51, and 1.75) for trials S, U, and W, respectively. There was no significant correlation in thrips damage ratings between the greenhouse and field tests for trials W and U.
In the second study, trial FV that consisted of 32 lines including glanded and glandless checks was evaluated in the greenhouse to examine the response to VW infections. Results indicated that there was no significant difference at a P < .05 level between the genotypes for glanded versus glandless in the first screening at 38 days post inoculation (DPI). But significant genotypic variation was detected in the second screening at 69 DPI, which gave the heritability estimate of 0.56, indicating that one half of the phenotypic variation in VW resistance is due to genetic factors. There was no significant difference between the glanded (4.33) and glandless (4.56) checks at 69 DPI. Five glandless lines including SA 2248 (3.12), 10NM11-17 (3.20), 12Y1039-1 (3.38), 12Y1020-1 (3.56), and 10NM11-13 (3.63), exhibited significant lower VW resistance ratings than both the glanded and glandless checks.
The eight replicated greenhouse tests showed that glandless cotton lines maybe carry some levels of resistance to thrips and Verticillium wilt in cotton and therefore can be used in cotton breeding programs as a new source of parents to develop glandless cotton cultivars for thrips and VW resistances.
|Commitee:||Sengupta-Gopalan, Chanpa, Idowu, John, Wang, Tonghui|
|School:||New Mexico State University|
|Department:||Entomology, Plant Pathology, and Weed Science|
|School Location:||United States -- New Mexico|
|Source:||MAI 81/6(E), Masters Abstracts International|
|Subjects:||Botany, Genetics, Soil sciences|
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