No abstract

Antixenosis and antibiosis in the resistance of common beans (Phaseolus vulgaris L.) to the melon thrips, Thrips palmi Karny, were investigated under laboratory and field conditions. Experiments were conducted for four moderately resistant genotypes ('Brunca', BH-130, EMP 486, and FEB 115) in comparison with one susceptible genotype (APN 18). Multiple-choice tests recorded most thrips on EMP 486 and least on FEB 115. Dual-choice tests conducted in both laboratory and field confirmed the antixenotic effect of FEB 115 and the attractant effect of EMP 486 on thrips. These results demonstrate the significance of antixenosis in the resistance of common beans to T. palmi. Life-table studies showed significant differences in egg duration, immature and adult survivorship, female body length and longevity, daily oviposition rate, and total fecundity among the bean genotypes. The intrinsic rate of natural increase (r(m)) and its associated population parameters varied significantly with the bean genotype on which T. palmi cohorts were reared. Based on mean r(m) values, the five bean genotypes can be divided into two groups, with BH-130 and 'Brunca' being less favorable for the population growth of thrips than EMP 486 and FEB 115; the latter were comparable to the susceptible genotype APN 18. These life-table results indicate the role of antibiosis in enhancing the resistance of common beans to T. palmi.

Host plant resistance in common bean (Phaseolus vulgaris L.) is a promising component in an integrated cropping system for managing thrips (Thrips palmi Karny) infestation. This study was conducted to identify quantitative trait loci (QTLs) for resistance to thrips in common bean, using F5:7 recombinant inbred lines (RILs) as a mapping population. The RILs, derived by single seed descent (SSD) of the cross of two Mesoamerican bean lines, BAT 881 and G 21212, were found to show transgressive segregation for thrips resistance in the field. Correlations between damage and reproductive adaptation (RA) scores were significant within and between seasons. The QTLs for both traits were located based on single interval mapping (IM) and joint interval mapping (JIM) analysis using a genetic map constructed with microsatellite and random amplified polymorphic DNA (RAPD) markers. Eight of eleven resulting linkage groups (LGs) were shown to be homologous to chromosomes of the integrated linkage map of common bean. A major QTL for thrips resistance located on LG b06 explained up to 26.8% of variance for resistance in a single season and was named Tpr6.1. The JIM across several seasons revealed various QTLs on LGs b02, b03, b06, and b08, some of which were located at regions of genes encoding for disease resistance. The identification and mapping of thrips‐resistance genes is expected to facilitate the development of resistant bean cultivars by using molecular marker‐assisted selection.

Resistance in beans, Phaseolus vulgaris L., to the melon thrips Thrips palmi Karny was studied under field conditions at two sites in Colombia. Genotypes were rated for resistance on the basis of visual damage scores, bean production ratings (a visual estimate of pod and seed set), and grain yields. Of 1,138 genotypes tested, only 60 (5.3%) were rated as resistant. Repeated testing allowed us to identify potential sources of resistance in five germplasm accessions (G 02402, G 02852, G 03177, G 03569, and G 04055), one commercial variety ('Brunca'), six elite breeding lines (A 216, DOR 714, EMP 486, FEB 115, FEB 161, and FEB 162), 41 recombinant inbred lines derived from the BAT 881 x G 21212 cross, and seven recombinant inbred lines derived from a cross between DOR 364 and BAT 477. Resistance was not associated with maturity, growth habit, pubescence, and seed color or seed size. In general, correlations between visual damage scores and bean production ratings and between damage scores and yield were high and significant meaning that selection on damage rating is useful to identify genotypes that may have tolerance as a mechanism of resistance. The continuous distribution of damage scores of 139 recombinant inbred lines suggested that the inheritance of resistance to the melon thrips might be quantitative. Overall, resistance levels in beans can be considered as moderate, because none of the genotypes tested received damage scores of <3 on a 1-9 scale and none was ever rated as highly resistant in terms of bean production ratings.