|Dong, Weibo - UNIV OF GA|
|Brenneman, Timothy - UNIV OF GA|
|Mullinix, Benjamin - UNIV OF GA|
Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 20, 2007
Publication Date: August 1, 2007
Citation: Dong, W., Holbrook Jr, C.C., Timper, P., Brenneman, T.B., Mullinix, B.G. 2007. Effects of Inoculum Type, Inoculum Level, Inoculation Date, and Assessment Date on Evaluating Resistance to Meloidogyne arenaria in Peanut. J. of Nematology 39(2):169-175. Interpretive Summary: The peanut root-knot nematode causes significant losses to peanut production, and the development and use of resistant varieties is desirable. The purpose of this study was to develop a more rapid method for identifying peanut that are resistant to nematodes. Greenhouse trials were conducted to evaluate different nematode inoculation systems, and different resistance rating systems. Based on the results of these study, we propose a two-stage greenhouse screening to identify peanut genotypes with nematode resistance. A preliminary screen would first be used to eliminate susceptible genotypes based on the amount of root galling 14 days after inoculation with 8000 eggs. The selected genotypes should then be assessed for egg mass index or egg number per gram fresh root at 6 weeks after inoculation to verify the resistance.
Technical Abstract: Use of resistant cultivars is a desirable approach to manage peanut root-knot nematode (Meloidogyne arenaria), and reliable, efficient screening methods are needed. To optimize the resistance screening protocol, a series of greenhouse tests were done using seven genotypes with three levels of resistance to M. arenaria. The three resistance levels could be separated based on gall index as early as 2 weeks after inoculation (WAI) using 8000 eggs/plant, while 4 or more weeks were needed when 1000-6000 eggs/plant were used. High inoculum densities (over 8000 eggs/plant) were needed to separate the three resistance levels based on eggs/g root within 8 WAI. A gall index based on percentage of galled roots could separate the three resistance levels at lower inoculum levels and earlier harvest dates than other assessment methods. The use of eggs vs second-stage juveniles (J2) as inoculum provided similar results; however, it took 3-5 more days to collect J2 than to collect eggs from roots. Plant age affected gall index and nematode reproduction on peanut, especially on the susceptible genotypes AT201 and D098. The genotypes were separated into their correct resistance classes when inoculated 10 to 30 days after planting, but were not separated correctly when inoculated on day 40.