Newsletter 140C

Abstract

Breeding programs for nematode resistance in common bean require the identification and characterization of resistance sources among genotypes against local nematode populations. The reactions of 24 genotypes of dry and snap beans from Iran and CIAT (International Center for Tropical Agriculture, Colombia) were investigated against the Iranian population of Meloidogyne javanica and M. incognita race 2 under greenhouse conditions. To this objective, two independent experiments for each nematode species (inoculum = 5000 Juvenile 2 and eggs/plant) were carried out. Individual plants were harvested to determine the two most reliable values of nematode resistance indices viz. resistance index (RI) that was calculated using combined values of galling and egg mass production indices, and the percent reduction of reproduction index that was generated using nematode reproduction factor. Among the genotypes, Alabama # 1 showed resistance to both nematode species with RI = 14.5 and 11.5 for M. javanica and M. incognita race 2, respectively. In contrast, all the other 23 genotypes were susceptible and/or highly susceptible to M. javanica (RI = 132.75–162) and M. incognita race 2 (RI = 113–162) in two experiments, respectively. Several genotypes including Carioca, Enxofre, Mulatinho Comun, and Rio Doce, previously reported as resistant or moderately resistant to different M. incognita populations, resulted highly susceptible to both nematode populations from Iran. This study showed different responses of bean genotypes to distinct geographical populations/strains of root-knot nematodes.