Genetics of reniform nematode resistance in Gossypium arboreum germplasm line PI 529728

Authors: Erpelding, John; Stetina, Salliana - Sally

Submitted to: Journal of Plant Breeding and Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2013
Publication Date: 7/1/2013
Citation: Erpelding, J.E., Stetina, S.R. 2013. Genetics of reniform nematode resistance in Gossypium aboreum germplasm line PI 529728. Journal of Cotton Science. 1:48-53.

Interpretive Summary: Reniform nematode is a microscopic round worm that lives in the soil and feeds on plant roots. No commercial upland cotton varieties are resistant to reniform nematode and yield losses in the U.S. are estimated at $100 million annually. Resistance to the nematode has been found in related cotton species, such as the diploid cotton species Gossypium arboreum. However, this species has 26 chromosomes compared to the 52 chromosomes found in commercial cotton, and this difference in chromosome number requires specialized breeding methods in order to transfer resistance to commercial cotton varieties. Understanding the number of genes and how they function can increase the success in transferring resistance to upland cotton and the development of resistant breeding lines for cotton improvement. The Gossypium arboreum germplasm line PI 529728 was identified as resistant to the nematode and was crossed with highly susceptible line PI 529729 to determine the number of genes responsible for the resistance. Evaluation of the resulting offspring indicated that resistance was controlled by a single recessive gene, and less than 25% of the offspring were resistant. Additionally, some of the offspring showed higher levels of resistance than the resistant parent PI 529728, which will be useful in the development of resistant varieties. This resistance is being transferred to upland cotton, and results of this study suggest a larger number of plants should be evaluated to successfully identify upland cotton breeding lines with the new source of reniform nematode resistance.

Technical Abstract: Reniform nematode (Rotylenchulus reniformis) has emerged as a serious pathogen of cotton in the United States and management of the nematode has been difficult due to the lack of resistant upland cotton (Gossypium hirsutum) varieties. However, resistance has been frequently observed in diploid cotton species; although, transferring the resistance to tetraploid cotton is hindered by differences in chromosome number and chromosome pairing incompatibility of the different genomes. The 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 and F2 populations. The populations were screened for nematode resistance in a plant growth room under controlled environmental conditions. The 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 approximately 28 days after inoculation. The two populations showed quantitative variation in the number of swollen females per gram of root. Plants supporting 40% or less of the infections that developed on the susceptible control genotype G. hirsutum ‘Deltapine 16’ were considered resistant. Based on this classification of susceptibility and resistance, it was predicted that a single recessive gene was conferring resistance observed in PI 529728. This information will aid in the introgression of R. reniformis resistance from PI 529728 into upland cotton for the development of resistant varieties.