Inheritance of resistance to Meloidogyne spp. in common bean and the genetic basis of its sensitivity to temperature.

Bean lines PI 165426, PI 165435, and Alabama no. 1, possessing resistance to Meloidogyne incognita, and bean lines A315 and A445, possessing gene Me1, were tested against several Meloidogyne incognita and M. javanica isolates. Resistance in bean line PI 165426, PI 165435, and Alabama no. 1 was found to be complementary to resistance conferred by gene Me1. Resistance in PI 165426 was found to be dominant and conditioned by one dominant and one recessive gene at 26 °C. We propose Me2me3 as the genotype symbol for this resistance. Resistance in lines PI 165435 and Alabama no. 1 was found to be recessive. Since Alabama no. 1 and PI 165435 were resistant at 26 °C but susceptible at 29 °C, and segregation of F2 progeny derived from crosses involving PI 165426 was 13∶3 at 26 °C and 1∶2∶1 at 28 °C, we concluded that the temperature at which transition from resistance to susceptibility occurs was determined by whether the resistance gene is dominant or recessive. Furthermore, the 1∶2∶1 segregation of F2 plants and an intermediate resistance reaction of F1 plants of crosses involving PI 165426 indicated that allelic dosage of the dominant gene also influenced the transition temperature.