Tomato hairless on stems mutant affects trichome development

Trichomes are hair-like structures derived from plant epidermal cells. Trichomes exist in most plant species and are categorized as either glandular or non-glandular. Glandular trichomes function as chemical protection against herbivores, while non-glandular trichomes serve as physical barriers to various biotic and environmental stresses. Here, we describe a novel recessive mutation named hairless on stems ( host ) which was identified based on the absence of trichomes on stems. host plants exhibited lower density of trichomes on leaves, stems, and hypocotyls, compared with the wild-type (WT) plants. Types I, III, and V trichomes, especially, were not developed at all on the stems of the host plants. In addition to trichome initiation, the length of Type I trichomes was shorter in the host plants than in the WT plants. The growth of host plants under greenhouse conditions showed that the mutant has shorter stems and fewer leaves than the WT plants. Genetic mapping of the host locus using the map-based cloning approach positioned the locus within 4.4 cM interval flanked by markers, Solyc09g074280 and Solyc09g075360, on chromosome 9. The identification of the Host gene will provide a clue for understanding multicellular trichome development in tomato and the Host gene can be used as a useful genetic resource to develop insect-resistant tomato.