Nematropica (2011) 41, 68-74

R.B. Sikkens, D.B. Weaver, K.S. Lawrence, S.R. Moore and E. van Santen (2011)
LONREN upland cotton germplasm response to Rotylenchulus reniformis inoculum level
Nematropica 41 (1), 68-74
Abstract: Rotylenchulus reniformis (reniform nematode) can be a yield-limiting factor for upland cotton. Resistance to this nematode was discovered in a wild cotton relative, transferred to an upland background and released as the germplasm LONREN. The LONREN source of resistance to reniform nematode in upland cotton was evaluated for reaction to increasing levels of inoculum on root and shoot growth and nematode reproduction compared to susceptible genotypes. Genotypes tested were LONREN-1 and LONREN-2 (resistant); Fibermax 966 and Deltapine 555BR (susceptible); and one susceptible and one resistant F2:4 line from the cross LONREN-1 × Fibermax 966. Inoculum levels of 0, 500, 1000, 5000, 10,000, or 50,000 juveniles and vermiform of R. reniformis were used. Plant height and vigor ratings were collected weekly. Root and shoot fresh and dry mass, and nematode numbers were collected 60 days after inoculation. Based on inoculation rate, a reproduction factor (Rf) was calculated as the ratio Pf/Pi, where Pf = final nematode population and Pi = initial inoculum level. Root dry mass of genotypes with the LONREN resistance source was reduced at high inoculation density compared to low inoculum levels. An opposite trend was observed for root dry mass of reniform nematode susceptible genotypes, where root dry mass increased at higher inoculum levels. Shoot dry mass for all genotypes was largely unaffected except at the highest inoculum level. Shoot to root dry mass ratios for the LONREN resistance source genotypes were found to trend higher with increased inoculum levels, whereas the same ratios decreased in case of the susceptible genotypes. Examination of the roots of LONREN resistant source genotypes showed signs of necrosis. We conclude that the LONREN resistance source exhibits a type of hypersensitive response to reniform nematode. This reaction, while inhibiting reniform nematode reproduction, appears to be a factor in seedling stunting at higher nematode density levels.
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Database assignments for author(s): David B. Weaver, Kathy S. Lawrence

Research topic(s) for pests/diseases/weeds:
resistance/tolerance/defence of host

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Rotylenchulus reniformis	Cotton (Gossypium)