Submitted to: Journal of Nematology
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2012
Publication Date: N/A
Interpretive Summary: N/A
Technical Abstract: Root-knot nematodes (RKN) are an important re-emerging pest of melon (Cucumis melo), due largely to the loss of methyl bromide as a pre-plant soil fumigant. Melon is highly susceptible to southern RKN, Meloidogyne incognita, which causes severe root galling and reduced melon fruit yields. Cucurbit rootstocks have been used to control soilborne diseases, such as Fusarium wilt in grafted melon in Asia since the 1920s. During the last decade, grafting melon on resistant rootstocks has been considered a potential alternative to methyl bromide for managing soilborne diseases and pests on this crop in the U.S. We evaluated the response of commercial and wild-type cucurbit rootstocks representing different cucurbit species to M. incognita in greenhouse and field tests. Greenhouse test. In a greenhouse evaluation of 23 commercial cucurbit rootstocks and Plant Introductions (PIs) that can be used for grafting melon, PIs of African horned cucumber, Cucumis metulifer, exhibited the least (P<0.05) root galling among four cucurbit rootstock taxa with root gall indices (GI) ranging from 2.6 to 3.3, using a 1.0 to 5.0 scale where 1=0% to 3% root system galled and 5=80% to 100% root system galled. The Cucumis melo commercial melon rootstocks ‘Dinero’ and WR-15006 were highly susceptible with GI= 4.9 and 4.7, respectively. Likewise, three commercial Cucurbita moschata rootstocks and one PI (BS1, TZ 148, AQ, and PI 53009, respectively) were also susceptible with GI ranging from 4.5 to 4.7. Twelve Cucurbita maxima x C. moschata commercial squash hybrid rootstocks had GI ranging from 4.2 for ‘Carnivor’ to 5.0 for Jing Xin No.3. The standard Cucurbita maxima x C. moschata hybrid ‘Strong Tosa’ also was highly susceptible with GI=4.9. Field test, Charleston, SC. The scion ‘Athena’ melon (C. melo) was grafted on eight different cucurbit rootstocks and evaluated in a field that was highly infested with M. incognita. Rootstocks of Benincasa hispida, Cucurbita maxima x C. moschata, Cucurbita argyrosperma, C. melo, C. maxima, and Cucurbita ficifolia were all highly susceptible to RKN with numbers of M. incognita eggs per gram fresh root ranging from 659 for B. hispida to 6,793 for C. argyrosperma. Cucumis metulifer exhibited moderate resistance and supported 323 eggs per gram fresh root. Thus, C. metulifer was the only cucurbit rootstock evaluated in our tests that exhibited resistance to M. incognita. Currently, we are evaluating all of the C. metulifer PIs in the USDA Plant Introduction collection in order to identify the most resistant and vigorous accessions for use in developing RKN-resistant rootstocks for melon.