Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/17/2001
Publication Date: 2/15/2002
Citation: Thies, J.A., Fery, R.L. 2002. Heat stability of resistance to southern root-knot nematode resistance in bell pepper genotypes homozygous and heterozygous for the N gene. Journal of the American Society for Horticultural Science. 127(3):371-375. Interpretive Summary: Southern root-knot nematodes (Meloidogyne incognita) are serious pests of bell peppers. Root-knot resistant, open-pollinated bell pepper cultivars such as 'Charleston Belle' have been developed by USDA, but none of the commercial bell pepper hybrid cultivars currently available to U.S. growers are resistant. The studies reported in this paper were conducted to determine if F1 hybrid bell pepper cultivars developed using only one resistant parent would be as resistant to root-knot nematodes as open- pollinated cultivars such as 'Charleston Belle'. We evaluated the resistant 'Charleston Belle' (CB), the susceptible 'Keystone Resistant Giant' (KRG), and their F1 hybrids [F1(CB X KRG) and F1 (KRG X CB)]at 75, 82, and 90 degrees F for resistance to M. incognita. In these studies, the F1 hybrids and the resistant parent ('Charleston Belle') exhibited high, moderate, and low resistance at 75, 82, and 90 degrees F, respectively. The resistant 'Charleston Belle' has substantial value for use as a parental line for development of root-knot resistant hybrid bell pepper cultivars. These hybrids should exhibit the same level of resistance as the resistant 'Charleston Belle' parent and should be useful for managing M. incognita in hot climates.
Technical Abstract: Expression of the N gene which confers resistance to Meloidogyne incognita in pepper, Capsicum annuum, is modified at high temperatures (28 and 32 C). However, expression of the N gene in the heterozygous (Nn) condition has not been documented at any temperature. Responses of two isogenic pepper lines (differing at the N resistance locus), and the F1 of the cross and its reciprocal were compared at 24, 28, and 32 C in a growth chamber experiment. Pepper lines used were: Charleston Belle (CB - NN), Keystone Resistant Giant #3 (KRG - nn), F1 (CB X KRG Nn), and F1 (KRG X CB - Nn). KRG was susceptible at all 3 temperatures. Response of Charleston Belle, F1 (CB X KRG - Nn), and F1 (KRG X CB - Nn) were similar; these lines exhibited high resistance at 24 C, but resistances were compromised at 28 C and 32 C. However, average root gall severity indices for the resistant lines were 67%, 61%, and 46% lower than for KRG at 24, 28, and 32 C, respectively. These results suggest that the NN and Nn conditions are expressed similarly at high temperatures and such cultivars may be useful for managing M. incognita in hot climates.