Location: Crop Genetics Research Unit
Title: Genetics of resistance to Rotylenchulus reniformis in Gossypium arboreum PI 529728 Authors
Submitted to: Journal of Nematology
Publication Type: Abstract Only
Publication Acceptance Date: July 14, 2013
Publication Date: N/A
Technical Abstract: Reniform nematode (Rotylenchulus reniformis) is a serious pathogen of cotton (Gossypium hirsutum) in the United States and management of the nematode has been difficult due to the lack of resistant upland cotton varieties. The moderately resistant G. arboreum germplasm line PI 529728 was identified as a potential new source of R. reniformis resistance. The inheritance of resistance was investigated for PI 529728 through the development of segregating populations for resistance screening. PI 529728 was crossed with the highly susceptible G. arboreum germplasm line PI 529729 to develop BC1F1 (PI 529728//PI 529729/PI 529728) and F2 (PI 529729/PI 529728) populations. The populations were screened for nematode resistance in a plant growth room under controlled environmental conditions. The 10 F1, 69 BC1F1, and 333 F2 plants were individually inoculated with 1,000 vermiform nematodes and the number of swollen females on the root systems was determined 28 days after inoculation. The F1 plants were susceptible indicating resistance was a recessive trait. The two populations showed quantitative variation in the number of swollen females per gram of root (FGR). When compared to the resistant parent PI 529728, 30 BC1F1 plants showed fewer FGR (mean 30, range 2-46). Assuming a 1:1 segregation ratio for the backcross population, classifying these plants as resistant would indicate a single recessive gene is conferring resistance (chi-square=1.17, P=0.2786). Assuming a single recessive gene model, 83 F2 plants would be predicted as resistant, which would indicate plants with 11 or fewer FGR would be classified as resistant. This value would be approximately a 45% reduction in FGR as compared to the mean of the susceptible control PI 529251. Ninety plants had 11 or fewer FGR, which would fit the single recessive gene model (chi-square=0.73, P=0.3930). This is the first report of a recessive gene conferring a useful level of R. reniformis resistance in G. arboreum, suggesting genetic diversity for resistance in the germplasm collection. Additionally, highly resistant plants were observed in the populations suggesting transgressive segregation for resistance. This information will aid in the introgression of R. reniformis resistance from PI 529728 into upland cotton for the development of resistant varieties.