RESPONSE OF FIVE RESISTANT COTTON GENOTYPES TO ISOLATES OF ROTYLENCHULUS RENIFORMIS COLLECTED FROM RENIFORM NEMATODE INFESTED FIELDS OF LOUISIANA
Reniform nematode (Rotylenchulus reniformis) is a significant cotton (Gossypium spp.) parasite in the southern United States, causing an estimated 4% yield loss. Variation in reproduction and pathogenicity across reniform nematode isolates collected from Louisiana on susceptible cotton has been reported. This greenhouse study was conducted to determine the response of five cotton genotypes that varied in resistance to the reniform nematode to five isolates of R. reniformis collected from Louisiana cotton fields. Across cotton genotypes, the Evan and Avoyelles reniform nematode isolates had higher reproduction (33,793 and 27,800 juveniles/250 g of soil, respectively) than the LA, Old Crop Rotation, and Oak Tree Cut isolates. Across reniform nematode isolates, the mean number of juveniles on G. arboreum (A2-190) and LONREN-2 (5,573 and 6,013 juveniles, respectively) was significantly lower than on Delta Pearl, TX-110, BARBREN-713 and LONREN-1 genotypes. There was a significant interaction between the cotton genotypes and reniform nematode isolates. However, all isolates exhibited the highest reproduction on the susceptible cultivar Delta Pearl, and less reproduction on all genotypes that had previously shown attributes of reniform nematode resistance. The LONREN-1, LONREN-2, and A2-190 genotypes displayed a hypersensitive reaction, characterized by reduced plant height, against the Evan and Avoyelles isolates that was greater than with the other isolates. This study demonstrates that there is variability in reproduction and pathogenicity among reniform nematode isolates in Louisiana. Based upon nematode reproduction, G. arboreum (A2-190) and LONREN-2 were the most resistant across all nematode isolates. With respect to pathogenicity, TX-110 and BARBREN-713 were the most tolerant to reniform nematodes and could be useful in developing cultivars that are both resistant and tolerant to the nematode.