Evaluation of Resistance Mechanism of some navy bean genotypes to two-spotted spider mite (Tetranychus urticae)

In order to evaluate the resistance mechanism of Navy Bean (Phaseolus vulgaris L.) to two-spotted spider mite (Tetranychus urticae Koch), an experiment was conducted in greenhouse conditions during 2009-2010. Efficient mechanism of resistance including antibiosis, antixenosis and tolerance of 50 genotypes of navy bean was evaluated using standard greenhouse tests. All experiments followed a complete randomized design (CRD) with 3 replications and 50 treatments (Genotypes). Analysis of variance and mean values comparison using the Duncan procedure showed that there was significant difference between three mechanisms of resistance in 50 genotypes at 5 % level. The most response of antibiosis was seen in genotype numbers 41188, 41103, 41117, 41190, 41109, 41111, 41161, 41178, 41106, 41127, 41133 and 41151. Genotype numbers 41188, 41121, 41158, 41113, 11867 and 41101 were the most tolerate genotypes. 16 genotypes showed the most response of antixenosis. To appraise the Plant Resistance Index (PRI) used the reverse product of values of resistance mechanisms and genotype numbers 41151 and 41134 showed the highest and lowest values, respectively. Our results show that genotype numbers 41151, 41121 and 41188 have the most potential of resistance to this pest with antibiosis and antixenosis as the principal mechanisms of resistance.