Date of Award

1985

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Abstract

Cotton, Gossypium hirsutum L., is a valuable cash crop in Louisiana that is grown primarily for its fiber. The reniform nematode, Rotylenchulus reniformis Linford and Oliveira, is a major pest of cotton in Louisiana, where it was first identified in 1941 and has now been found in 39 of 64 parishes. Nematicides and crop rotation are conventional methods of reniform nematode control, but resistant cultivars offer the most economical and practical method of control. The primary objective of this study was to examine and evaluate new and previously reported sources of reniform nematode resistance in cotton, which could eventually be incorporated into a breeding program. Genotypes were evaluated in the greenhouse and resistance based on reniform nematode egg production per gram of root. La. 434-1031-4 was resistant to reniform nematode whenever tested. Several race stocks and day-neutral converted race stocks expressed resistance. These were TR 19, converted TR 19, TR 26, converted TR 26, converted TR 75, converted TR 78, TR 176, converted TR 176, and Texas 110. Gossypium longicalyx L., which had been reported as having immunity, expressed immunity or near-immunity in these tests. Data from triploids and hexaploids (G. longicalyx x G. hirsutum Acala) suggest strong dominance for the immunity or near-immunity factor(s). G. longicalyx could be used as a resistant parent, once limiting factors in inter-specific hybridization are solved. A field test to determine relative resistance was conducted in 1985. Four of the more resistant genotypes with good agronomic properties, chosen from greenhouse tests, were compared to 'Deltapine 41' for reniform nematode egg production, green plant weight, white flower production, plant height, reniform nematode population, and boll number. The four genotypes (Auburn 80-180, Auburn 634, La. 434-1031-810909, and La. 434-1031-810910) were resistant based on field evaluations. Auburn 80-180 and Auburn 634, two advanced breeding lines with resistance to root-knot nematode, Meloidogyne incognita acrita (Kofoid and White) Chitwood, La. 434-1031-810909, La. 434-1031-810910, and La. 434-1031-4 would make good resistant parents in a breeding program.

Pages

108

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