Heat Stability of Resistance to Meloidogyne incognita in Scotch Bonnet Peppers ( Capsicum chinenseJacq.)

Abstract

Stability of resistance to Meloidogyne incognita (Kofoid & White) Chitwood was determined in pepper (Capsicum chinense Jacq. and C. annuum L.) at 24, 28, and 32ºC. Reactions of the C. annuum cultivars Charleston Belle and Keystone Resistant Giant and the C. chinense cultigens PA-426 and PA-350 to M. incognita were compared. Charleston Belle is homozygous for the N gene that confers resistance to M. incognita in C. annuum, and Keystone Resistant Giant is the susceptible recurrent parent of Charleston Belle. PA-426 is homozygous for a single dominant resistance gene that is allelic to the N gene, and PA-350 is susceptible. Root galling, egg-mass production, numbers of eggs per g fresh root, and reproductive factor of M. incognita increased for all pepper genotypes as temperature increased. Severity of root galling and nematode reproduction were less for PA-426 and Charleston Belle compared to PA-350 and Keystone Resistant Giant at all temperatures. However, both PA-426 and Charleston Belle exhibited a partial loss of resistance at the higher temperatures. For example, at 32ºC, the numbers of M. incognita eggs per g fresh root and the reproductive index for PA-426 and Charleston Belle were in the susceptible range. Nevertheless, the gall index for both cultivars was still within the resistant range. Both PA-350 and Keystone Resistant Giant exhibited highly susceptible reactions at 28 and 32ºC. Although the resistances of PA-426 and Charleston Belle were somewhat compromised at high temperatures, cultivars possessing these resistances will still be useful for managing M. incognita under high soil temperatures.