Field studies were conducted on an Hidalgo sandy clay loan soil at Weslaco, TX to evaluate 15 upland cotton cultivars in the presence on the reinform nematode (Rotylenchulus reniformis) and to ascertain the effects of the reniform nematode on plant growth, lint yield, and fiber quality. The experimental plots were located in an area with a known history of reniform nematode occurrence. Experimental design was a 2x15 factorial in a split-plot arrangement, with four replications. The Telone II-treated (control) and non treated areas were considered whole plots and cultivars as subplots. Telone seedbeds (8 inch depth) for the treated plots 10 weeks prior to planting in order to eliminate or significantly reduce the reniform nematode population. Nematode population were determined on March 28 and August 9, 1991. Initial sampling indicated that the untreated and Telone ii-treated plots had populations of 34 and 2 nematodes/100 cc of soil in the untreated plots, while the control plots had an average of 18 nematodes/100 cc soil sample.

Cultivars were observed to differ for growth rate, lint yield, and fiber quality in both the reniform infested and control plots. In the untreated plots, slower growth rates and lower lint yields were detected for cultivars Stoneville 453, B9-D344, B9-AC2086, LA4-4, LA909, LA910, Lankart 57, and C120. The fastest growth rates occurred for C110 and C32, while the highest yields obtained in the reniform infested plots were achieved by C120xDPL20, a F₁ hybrid, and C21S781-2. In the Telonetreated pots, Stoneville 453, B9-D344, and B9-AC2086 had the slowest growth rates and produced the lowest yields.

Treatment means were also observed to be significantly different for the following measurements: 1) number of true leaves at 30 and 48 days after planting (DAP), 2) plant height at 30 DAP, 3) terminal growth rate, and 4) lint yield. All of the above measurements were significantly reduced in the reniform infested plots. When lint yields of each cultivar were compared between treatments, it was observed that yield reductions caused be the reniform nematode were lowest for LA1032 (13%), C21S781-2 (27%), C32 (28%), and LA910 (29%). The greatest yield reductions occurred for LA4-4 (51%), Lankart 57 (47%), Stoneville 453 (46%, and LA887 (43%). Fiber quality measurements were not generally affected by reniform nematodes, however, micronaire was observed to be significantly reduced in the untreated plots. In addition, the reniform infestation appeared to retard seed development, as evidenced by a lower seed index and higher percentage of immature seed in the untreated plots.

In this study, reniform nematodes, a parasitic pest of cotton was observed to reduce plant growth and growth rate, lint yield, micronaire value and seed index. The 15 cultivars evaluated were also observed to differ in growth and yield response to the reniform nematode. Identifying cultivars which show tolerance or the ability to escape or minimize the delterious effects of the reniform nematode should provide useful information genetic improvement programs.