Submitted to: Journal of Nematology
Publication Type: Abstract Only
Publication Acceptance Date: May 1, 2009
Publication Date: July 12, 2009
Citation: Davis, R.F., Earl, H.J., Timper, P. 2009. Effect of simultaneous drought stress and root-knot nematode infection on cotton yield and fiber quality. Journal of Nematology. 41:323. Technical Abstract: Both drought stress and root-knot nematode (Meloidogyne incognita) infection can reduce cotton yield, and drought can affect fiber quality, but it not known what effect the nematodes have on fiber quality. To determine whether nematode parasitism affects fiber quality and whether the combined effects of nematode and drought stress on yield are additive (independent effects) or synergistic, we conducted a study in a field infested with M. incognita. A split-plot design was used in which the main plot factor was one of three irrigation treatments (drought, moderate water stress, and water-replete) and the sub-plot factor was one of two nematicide levels (1,3-dichloropropene at 0 or 56 l/ha). Surface drip tape irrigation was used for the three irrigation treatments. We prevented water stress in main plots designated as water-replete by irrigating twice weekly or as required. Drought plots received no irrigation, and the middle water stress treatment received half the water applied to the water-replete treatment. The severity of root galling was greater in non-fumigated plots and the severity increased as the level of water stress increased, but the degree of water stress did not influence the effect of fumigation. Cotton fiber length, weight of seed, and weight of lint produced were reduced in non-fumigated plots and decreased as the level of drought stress increased, but the degree of water stress did not influence the effect of fumigation. Fiber length and micronaire are two principal measures of fiber quality. Micronaire is a complex index that is affected by fiber wall thickness, and significant price reductions are applied to cotton with micronaire outside of specified ranges. Micronaire was increased by moderate to severe drought stress, but micronaire was not affected by fumigation. Therefore, we conclude that parasitism of cotton by M. incognita can affect fiber quality by reducing fiber length, and the detrimental effects of nematode parasitism and drought stress are additive rather than synergistic.