. Host plant resistance would provide an economical and environmentally friendly alternative for managing root-knotnematodes in watermelon.
There are several reports describing the reactions of cultivated watermelon to root-knotnematodes. Seventy
presence was associated with higher levels of RKN resistance, and both QTL combined accounted for ≈6% of the observed variation in the number of EM.
Association of AFLP markers with QTL z for root-knotnematode (RKN) resistance in
bean and snap bean crops, little effort has been deployed toward obtaining resistant cultivars.
Some studies demonstrate the existence of genetic variability for root-knotnematoderesistance among bean accessions ( Mullin et al., 1991 ; Omwega and
pepper genotypes used in these studies were the bell pepper cultivars, ‘Charleston Belle’ ( NN ), ‘Keystone Resistant Giant’ ( nn ), ‘Carolina Wonder’ ( NN ), and ‘Yolo Wonder B’ ( nn ) that differ in resistance to root-knotnematodes controlled by the N
of Meloidogyne incognita on Cucumis melo var. texanus J. Nematol. 45 58 65 Fassuliotis, G. 1967 Species of Cucumis resistant to the root-knotnematode, Meloidogyne incognita acrita Plant Dis. Rpt. 51 720 723 Fassuliotis, G. 1970 Resistance of
107(6)A3’ to five Meloidogyne species in comparison with M. incognita- susceptible cultivar California Wonder after 30 d from inoculation. Although the ‘UFRJ107(6)A3’ line has shown resistance to four root-knotnematode species M. incognita , M
The southern root-knot nematode, Meloidogyne incognita [(Kofoid & White) Chitwood], causes serious economic losses to melon (Cucumis melo L.) production in the United States. The present study was conducted to determine if separable differences in nematode resistance of Cucumis melo could be found at some inoculum level. Five C. melo lines were compared with Cucumis metuliferus Naud. (C701A), a highly resistant species, for root necrosis, galling, egg mass production, and reproduction when inoculated at 0, 500, 1000, 2000, or 5000 nematode eggs per plant. Using these criteria, melon line C880 inoculated with 1000 eggs per plant was highly susceptible, while PI140471, PI 183311, and the cultivars Chilton, Georgia 47, Gulf Coast, Planters Jumbo, and Southland were less susceptible. In greenhouse tests with an inoculum level of 1000 eggs per plant, low levels of resistance were evident. A thorough screening of the available germplasm against M. incognita may identify higher levels of root-knot nematode resistance for incorporation into improved melon cultivars.
Five peach rootstock selections show immunity to root-knot nematode disease caused by Meloidogyne incognita (Kofoid and White) Chitwood and M. javanica (Treub) Chitwood. These are the first peach rootstocks which remain free from galls when exposed to both these root-knot nematode species. They are derived from a 1949 cross in Chico, California, of Prunus davidiana Franch with a Chinese Peach.
Resistance to the species M. incognita and M. javanica depends on different genes. Resistance to the former was inherited as a monofactorial dominant. Resistance to M. javanica appeared dependent on 2 or more dominant genes in both ‘Okinawa’ and P. davidiana, but P. davidiana progenies were completely free from visible galls.
A third type of root-knot nematode was discovered in Florida in 1966. It reproduces readily on ‘Okinawa’, ‘Nemaguard’ and the other lines which have been selected for resistance or immunity to M. incognita and M. javanica.
The grape Vitis champinii Planchon is one source of nematode resistance in grape rootstocks. Several selections valued for their resistance to the root-knot nematode (Meloidogyne incognita), a serious pest of grape production, are used as rootstocks and in rootstock variety development. However, V. champinii-based rootstock varieties are faulted for their excess vigor and susceptibility to other root pests. Root-knot nematode populations with the ability to damage important V. champinii-based rootstocks have been identified and may become more common. Other V. champinii accessions might be sources of nematode resistance genes with different specificities or might have more suitable horticultural characteristics than V. champinii varieties in commercial use. Nine V. champinii accessions from the National Clonal Germplasm Repository, Davis, Calif., and a V. champinii rootstock variety were screened for resistance to M. incognita. Resistance was assessed by counting eggs produced per root system. Eight of ten V. champinii accessions did not support nematode reproduction. Susceptible accessions supported lower nematode reproduction than susceptible V. vinifera control varieties. Progeny testing from crosses of resistant and susceptible accessions suggests that a dominant and a recessive gene may condition root-knot nematode resistance.