Histological changes in Gossypium hirsutum associated with reduced reproduction of Rotylenchulus reniformis

The reniform nematode (Rotylenchulus reniformis) is an important parasite of upland cotton (Gossypium hirsutum). Parasitism involves the formation of syncytia to provide nutrition for the female. Events that occur at the feeding site may determine the degree of susceptibility of cotton plants to reniform nematode. The objective of this work was to describe histological modifications associated with reduced reproduction of Rotylenchulus reniformis in upland cotton roots. 'Deltapine 50' cotton and a selection from this line with a moderate level of resistance were inoculated with reniform nematode in the greenhouse, and observations on roots were made 3, 6, 9, 12, and 15 days after inoculation. No differences in penetration behavior or in the formation and characteristics of syncytia were observed. Reduced reproduction was correlated with an earlier degeneration and collapse of the syncytial cells, and occasionally, with lack of hypertrophy of the pericycle cells involved. These two mechanisms accounted for 40% to 60% reduction of reproduction of reniform nematode in the plants examined.