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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #174072
Title: THE CUMULATIVE EFFECT OF MODERATELY-RESISTANT COTTON ON M. INCOGNITA POPULATION DENSITIES AFTER TWO YEARS

Author
item Davis, Richard

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Abstract Only
Publication Acceptance Date: 2/1/2005
Publication Date: 6/1/2005
Citation: Davis, R.F. 2005. The cumulative effect of moderately-resistant cotton on M. incognita population densities after two years [abstract]. In: Proc. of 2005 Beltwide Cotton Conferences, January 4-7, 2005, New Orleans, LA. p. 148.

Interpretive Summary:

Technical Abstract: There are no cotton cultivars for the southeastern U.S. with a high level of resistance to Meloidogyne incognita, the southern root-knot nematode, though there is at least one cultivar with a moderate level of resistance. However, previous studies have indicated that the benefit of a moderate level of resistance is relatively small within a single growing season. The hypothesis for this study is that growing a moderately-resistant genotype for a single year may have little effect, but the cumulative effect after two or three years may provide a significant benefit. This project was initiated to investigate the cumulative, multi-year effect on nematode population density and yield loss of growing cotton with a moderate level of root-knot nematode resistance. A split-plot design with six replications was used: whole plots were cotton genotypes with differing levels of root-knot nematode resistance and sub-plots were fumigated or non-fumigated to allow maximum and minimum nematode pressure. DP458 B/R was used as a susceptible standard, Phytogen 3196 was used a moderately-resistant genotype, and Acala NemX was used a resistant standard. Fumigated plots received 6 gal/a of Telone II (1,3-dichloropropene). After one cotton crop, mean nematode levels in non-fumigated plots were higher (P'0.05) following DP458 B/R (302/150 cm3 soil) than following Phytogen 3196 or NemX (73 and 30/150 cm3 soil, respectively), which did not differ from each other. Root gall indices (0-10 scale based on the percentage of the root system galled) in non-fumigated plots were higher (P<0.05) following DP458 B/R (5.7) than following Phytogen 3196 or NemX (0.9 and 0.6, respectively), which did not differ from each other. Mean nematode levels in non-fumigated plots after the second cotton crop were higher (P<0.05) following DP458 B/R (323/150 cm3 soil) than following Phytogen 3196 (80/150 cm3 soil), which was higher (P<0.05) than following NemaX (23/150 cm3 soil). Root gall indices in non-fumigated plots were higher (P<0.05) following DP458 B/R (3.2) than following Phytogen 3196 or NemX (0.6 and 0.1, respectively), which did not differ from each other. The percentage yield suppression did not differ among cultivars in either year, though the numerical rankings were consistent. Percentage yield suppression in the first year was 17.9% for NemX, 9.0% for DP458 B/R, and 6.4% for Phytogen 3196. Percentage yield suppression in the second year was 6.1% for NemX, 3.4% for DP458 B/R, and -5.0% for Phytogen 3196. The beneficial effect of a moderate level of resistance in cotton was significant after one growing season, and the effect was essentially the same after two seasons.