Resistance of watermelon germplasm to the peanut root-knot nematode

Thies, J.A.; Levi, A.

Resistance of watermelon germplasm to the peanut root-knot nematode

2003

Thies, J.A. | Levi, A.

Root-knot nematodes Meloidogyne arenaria (Neal) Chitwood, Meloidogyne incognita (Kofoid & White) Chitwood, and Meloidogyne javanica (Treub) Chitwood are serious pests of watermelon Citrullus lanatus (Thunb.) Matsum. & Nakai var. lanatus in the southern United States and worldwide. Watermelon cultivars with resistance to any of these nematode pests are not available. Therefore, we evaluated all accessions of Citrullus colocynthis (L.) Schrad.(21) and Citrullus lanatus (Thunb.) Matsum. & Nakai var. citroides (L.H. Bailey) Mansf.(88), and about 10% of C. lanatus var. lanatus (156) accessions from the U.S. Plant Introduction (PI) Citrullus germplasm collection for resistance to M. arenaria race 1 in greenhouse tests. Only one C. lanatus var. lanatus accession exhibited very low resistance root gall index (GI) = 4.9 and 155 C. lanatus var. lanatus accessions were susceptible (GI ranged from 5.0 to 9.0, where 1 = no galls and 9 = greater than or equal to 81% root system covered with galls). All C. colocynthis accessions were highly susceptible (GI range = 8.5 to 9.0). However, 20 of 88 C. lanatus var. citroides accessions were moderately resistant with a GI range of 3.1 to 4.0; overall GI range for the C. lanatus var. citroides accessions was 3.1 to 9.0. Resistance to M. arenaria race 1 identified in the C. lanatus var. citroides accessions was confirmed on a subset of accessions in a replicated greenhouse test. The results of our evaluations demonstrated that there is significant genetic variability within the U.S. PI Citrullus germplasm collection for resistance to M. arenaria race 1 and also identified C. lanatus var. citroides accessions as potential sources of resistance.

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