Tomato genotype resistance to whitefly mediated by allelochemicals and Mi gene.

Allelochemicals and Mi, nematode-resistant gene, are found in wild tomato species and can provide resistance to insect pests. The aim of this study was to check the resistance of tomato (Solanum lycopersicum L.) genotypes with different foliar allelochemical contents (acylsugar and/or zingiberene) associated with and not associated with the Mi gene against the whitefly (Bemisia tabaci biotype B). Fifteen tomato genotypes were tested for resistance against whitefly (Santa Clara, TOM-695, TOM-556, TOM-584, TOM-684, TOM-687, TOM-688, TOM-759, TOM-760, ZGB-703, ZGB-704, TOM-778, TOM-779, TOM-780, and PI-127826). Genotypes with high acylsugar (AS) (TOM-687 and TOM-688) as well as those with high zingiberene (ZGB) contents (ZGB-703 and ZGB-704) had lower oviposition and a lower number of nymphs when compared with genotypes with low AS and ZGB contents and without the Mi gene (Santa Clara, TOM-695, TOM-556, and TOM-584). The genotypes carrying the Mi gene, associated with low allelochemical contents, were less preferred for whitefly oviposition compared with susceptible genotypes with low AS and ZGB contents and without the Mi gene. When both the AS and ZGB allelochemicals were present in the same genotypes (TOM-778, TOM-779, and TOM-780), they showed a synergistic effect; the number of whitefly eggs and nymphs decreased in genotypes with high AS and ZGB compared with genotypes that had only one of these allelochemicals. However, the number of whitefly eggs and nymphs of genotypes with high AS and ZGB contents, individually or combined, was less than for genotypes carrying the Mi gene. These results indicate that allelochemicals are more effective than the Mi gene to provide resistance to whitefly. [ABSTRACT FROM AUTHOR]