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Effect of simultaneous water deficit stress and Meloidogyne incognita infection on cotton yield and fiber quality
R. F. DAVIS (1), H. J. Earl (2), P. Timper (1). (1) USDA ARS, Tifton, GA, U.S.A.; (2) University of Guelph, Guelph, ON, Canada

Drought stress and <i>Meloidogyne incognita</i> infection reduce cotton yield. Drought affects fiber quality, but nematode effects on quality are not known. To determine whether nematodes affect quality and whether the combined effects of nematodes and drought on yield and quality are independent, a seven year study was conducted in a field infested with <i>M. incognita</i>. A split-plot design was used with the main plot factor as one of three irrigation treatments (non-irrigated, moderate irrigation, and water-replete) and the sub-plot factor as 0 or 56 l/ha 1,3-dichloropropene. We prevented water deficit stress in water-replete plots by supplementing rainfall with irrigation. Moderate irrigation plots received half the water applied to water-replete plots. Root galling was greater in non-fumigated plots and in plots receiving the least irrigation, but irrigation did not influence the effect of fumigation on root galling (no irrigation×fumigation interaction). Lint and seed harvests were reduced in non-fumigated plots and also decreased as the level of irrigation decreased, but irrigation did not influence the effect of fumigation. Nematodes increased micronaire but typically had no effect on other fiber quality elements. Micronaire also was increased by water deficit stress, but the effects from nematodes and water stress were independent. We conclude that the effects of nematode parasitism and water deficit stress on cotton are independent and therefore additive.

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