Alternative methods of interpreting measurements of resistance to the leafhopper Empoasca kraemeri Ross and Moore in the common bean, Phaseolus vulgaris L.

Abstract

Phaseolus vulgaris, common bean, Empoasca kraemeri, leafhopper, components of resistance, resistance to insects . SUMMARY Appropriate definitions of, and methods of measuring, resistance are sought using Phaseolus vulgaris, a major source of protein in Latin America, and its most important pest, Empoasca kraemeri . The concepts of general vigour and narrow-sense resistance are defined : these two components make up broad-sense resistance . The validity of these definitions, which depend on the inclusion of tolerance as a resistance mechanism, is discussed . In order to distinguish the components, 38 genotypes of P . vulgaris were grown with and without insecticidal proctection, in three replications in a split-plot design, with three planting dates . Seed yield per plant, and a visual score of damage symptoms or vigour, were measured . Three methods of estimating narrow sense resistance are considered : 1) the genotype x insecticide interaction effect in a split-plots analysis, 2) the yield of each genotype unprotected (Y") divided by its yield protected (Yp), and 3) the deviation of each genotype from a regression of Y" on Yp . The third method overcomes some objections to the first two, and can be applied to damage and vigour scores as well as to yields . The 38 genotypes differed in narrow-sense resistance according to all three methods, and it appears that in practice Methods 2 and 3 were both valid . They also differed in general vigour . Breeders working with many pests and crops have found that low damage and high yield in the presence of the pest are effective selection criteria. The work reported here supports this view .

The inheritance of resistance to Empoasca kraemeri Ross & Moore in the common bean, Phaseolus vulgaris L.

“…Data were collected from three experiments described in an earlier paper (GALWEY & EVANS, 1982). Data were collected from three experiments described in an earlier paper (GALWEY & EVANS, 1982).…”

“…In each of these experiments, numerical scores based on visual assessment of E. kraemeri damage symptoms in the unprotected sub-plots, and of general vigour in the protected sub-plots and measurements of seed yield per plant, were taken using methods described in an earlier paper (GALWEY & EVANS, 1982). In each of these experiments, numerical scores based on visual assessment of E. kraemeri damage symptoms in the unprotected sub-plots, and of general vigour in the protected sub-plots and measurements of seed yield per plant, were taken using methods described in an earlier paper (GALWEY & EVANS, 1982).…”

“…P. vulgaris genotypes have been found to differ both in their general vigour and in their narrow-sense resistance to E. kraemeri (GALWEY & EVANS, 1982). This means that the genetically determined component of the variation in damage does have a detectable effect on the final seed yield.…”

“…Common bean genotypes differ both in their general vigour and in a more specific response to E. kraemeri which has been called 'narrow sense resistance' (GALWEY & EVANS, 1982). Common bean genotypes differ both in their general vigour and in a more specific response to E. kraemeri which has been called 'narrow sense resistance' (GALWEY & EVANS, 1982).…”

Quantitative trait loci for leafhopper (Empoasca fabae and Empoasca kraemeri) resistance and seed weight in the common bean

“…Resistance to E. kraemeri has been shown to be quantitatively inherited (CIAT 1978) with low heritability (Galwey and Evans 1982). Kornegay and Cardona (1990) reported that selections in the F 4 and F 5 generations generally produced lines with greater unprotected yields than did selections in the F 2 or F 3 generations.…”