Antixenosis and antibiosis of some melon (Cucumis melo) genotypes to the two-spotted spider mite (Tetranychus urticae) and a possible mechanism for resistance.

摘要

The existence of antixenotic resistance to the two-spotted spider mite [Tetranychus urticae Koch (Acari: Tetranychidae)] was investigated in 36 melon (Cucumis melo L.) genotypes using choice tests. The results revealed significant genetic diversity for this trait, and resistant ('Dastanbu 1', "Darunghermez', 'Zard-Jalali', and 'Kharboze') and susceptible ('Garmsari', 'Zard-khareji', 'Bargney', and 'Sabz') genotypes were identified. These four resistant and four susceptible genotypes were used in follow-up experiments in order to assess their mechanisms of antibiosis and related enzyme activities. Antibiosis data against T. urticae were collected by assessing the fecundity of mated female mites on melon leaf discs in the laboratory. The number of eggs laid by each female per day showed significant differences between genotypes. The lowest numbers of eggs were laid on 'Darunghermez' and 'Dastanbu 1', while the highest numbers of eggs were laid on 'Garmsari' and 'Zard-khareji'. The activities of both peroxidase and polyphenol oxidase increased in response to infestation by T. urticae in the resistant genotypes ('Dastanbu 1' and 'Darunghermez'). The resistant melon genotypes identified in this study may provide new sources of resistance against T. urticae in breeding programmes.