Diversity in Rotylenchulus reniformis reproduction biology impacts cotton growth and development

Reniform nematode (Rotylenchulus reniformis) is a predominant plant-parasitic nematode of upland cotton despite several decades of resistance breeding efforts. Substantial variability in reniform nematode has been reported, which could have impacted the resistance breeding efforts. The objectives of the current study were to i) determine the diversity in reniform nematode reproduction biology, and ii) understand how this diversity impacts cotton growth and development. Greenhouse studies involving nine geographic isolates representative of nine states in the US Cotton Belt (TN, AL, MS, TX, LA, AR, FL, SC, and GA) and two cotton cultivars (susceptible DP 2317 and resistant DP 2141) plus non-inoculated control suggested the diversity in reproduction biology (reproduction and virulence) exists among the nematodes. The AR isolate reproduced the most and displayed the greatest virulence, while the AL isolate reproduced the least and was the least virulent. The reproduction and virulence of other nematode isolates were intermediate. The nematode reproduction was 85% lower in the resistant cultivar relative to the susceptible cultivar. Additionally, nematode inoculation significantly impacted plant height, vigor, chlorophyll content, photosynthesis, and transpiration compared to the non-inoculated plants. Each isolate differed in its ability to impact cotton growth and development. Results from the current study suggested that reniform nematode resistance breeding programs in cotton must account for the diversity in reniform nematode reproduction biology for durable resistance.