Direct defense of common bean accessions against two-spotted spider mite (Tetranychus urticae Koch.) attack

To find the direct defense of seedling resistance of common beans, by resistant mechanisms, morphological and physiological attributes of ten cultivars (Naz, Dorsa, Akhtar,KS41128, 65-062-107, 65-071-98, 65-071-306, 65-071-410, 65-071-400, and 65-071-405) were evaluated against two-spotted spider mite in 2017 at Bu-Ali Sina university, Hamedan, Iran. Among four kinds of resistant mechanisms such as antixenosis, antibiosis, tolerant tests and PRI index, both antixenosis and tolerance mechanisms determined to be the most accurate tests in the evaluating of common bean resistance against TSSM attack. Germination delay, development and fast growth, early maturity, erected posture, small cotyledon area, the more leaf thickness along with the dark-colored demonstrated were the escape mechanisms of common beans tolerant genotypes against TSSM attack. Some epidermal traits such as the first defense barrier on common bean like hook-shaped and high density of trichome especially on abaxial epidermis by having trapping behavior showed high relation with tolerant genotypes. In fact, in tolerant beans, related-traits to trichome on leaves entrapped the body parts of TSSM such as leg tarsi, mouthpart and ovipositor and prevented to move, feed and reproduction of mites and therefore, these features decreased damage to leaf area of Phaseolus vulgaris as well. The 65-071-98, 65-062-107 genotypes and NAZ, were certainly categorized as the most tolerant cultivars while Akhtar and 65-071-400 were introduced as the most susceptible accessions of common beans, respectively.