Acylsugar and the role of trichomes in tomato genotypes resistance to Tetranychus urticae

Abstract

We evaluated the effect of tomato genotypes with a high content of acylsugar (AS) in the F2 generation on the behavior and biology of Tetranychus urticae, the two-spotted spider mite, the associated resistance mechanisms, and the role of trichomes in this resistance. Genotypes with a high AS content, and resistance to the spider mite (RVTA-2010pl#31 and RVTA-2010pl#94) were derived from interspecific crossing between wild accession LA-716 (Solanum pennellii, with high AS content), and cv. Redencao (S. lycopersicum, with low AS content). Free-choice and no-choice tests, and biological studies were conducted to determine the effect of genotype on the mite. The density and type of trichomes on both leaf surfaces and their correlations with AS and the assessed parameter were also determined. The results of the free-choice test demonstrated that the mites remaining on a plant and those laying eggs preferred the genotypes with low AS content to those with high AS content, thereby showing the non-preference resistance type. On the genotypes with high AS content, nymphs and adult females had a high mortality rate, adult females had a decreased oviposition rate, the duration of the egg incubation period increased, andviability of the egg and mite decresead. Thus, the mechanism of antibiosis was also associated in this resistance. A high density of type IV glandular trichomes was observed on the genotypes rich in AS. There was a significant positive relationship between AS content and density of type IV glandular trichomes. The density of glandular trichomes was positively correlated with mite mortality, and negatively correlated with attractiveness and oviposition.