Characteristics of the common bean, Phaseolus vulgaris, associated with resistance to the leafhopper Empoasca kraemeri

Abstract

SUMMARYExperiments were conducted using the common bean, Phaseolus vulgaris, and its most important pest in Latin America, Empoasca kraemeri, in order to assess the value of insect counts and various plant characteristics as selection criteria in a plant breeding programme. The combination of insect counts with measurements of damage symptoms should make it possible to distinguish tolerance from the resistance mechanisms of antibiosis and non‐preference. By this means, and by a knowledge of the plant characteristics associated with resistance, different forms of resistance may be combined in the progeny of crosses.In a comparison of two contrasting genotypes the more severely damaged genotype was the more heavily infested at early stages of plant growth, but had the lower level of infestation at later stages. The association of high early counts with high subsequent damage was not confirmed in an experiment on six genotypes, but the association of high damage with low late counts was partially confirmed. These results indicate that the level of early infestation of E. kraemeri is not consistently reflected in the subsequent levels of damage which P. vulgaris genotypes display. This suggests that these two criteria represent distinct forms of resistance which can be combined in hybrid progeny.Resistance was also associated with late maturity, indeterminate growth habit, purple flowers and black or beige seeds. However, consumer preferences and the requirements of agricultural systems place constraints upon the use of these relationships in resistance breeding.