The Role of Trichomes Type and Density in The Resistance Mechanism of Some Tomato Varieties to Tomato Leafminer Tuta Absoluta (Meyrick) (Lepidoptera: Gelechiidae)

Tomato leafminer Tuta absoluta is one of the most devastating pests of tomato (Solanum lycopersicum) worldwide. This study compared the distribution of the Tuta absoluta infesting three commercial Lycopersicon lycopersicum tomato varieties (Early girl, Roma and Rutgers) and two closely related Lycopersicon spp. presumed to be resistant (LA 716 and PI 134417) in response to leaflets trichomes. The number of Tuta absoluta mines blotches, larvae and damaged leaf area% were determined for individual leaflets on every half branch of five plants per variety. ÷In addition, the density of non-glandular and glandular trichomes were assessed in the same leaflet samples. T. absoluta infestations were only found on Early girl< Roma and Rutgers. Tuta absoluta mines, larvae, and damaged leaf area% were absent from the younger branches except Roma variety, appeared in the middle and increased toward the oldest branches indicating a positive relationship with leaflet and branch age. Obviously, the densities of both non-glandular and glandular trichomes were greatly higher in younger branches and gradually decreased in the mature or fully developed branches and oldest branches or senescing leaflets. No non-glandular trichomes were found on LA 716, but it had the greatest number of glandular trichomes than other tomato varieties. High negative correlation was found between number of mines, larvae and damaged leaf area and number of non-glandular and glandular trichomes. These results showed that commercial varieties have potential vulnerabilities to T. absoluta not present in closely related species suggesting plant attributes that could be exploited in breeding programs.