Automated imaging coupled with AI-powered analysis accelerates the assessment of plant resistance to Tetranychus urticae.

The two-spotted spider mite (TSSM), Tetranychus urticae, is among the most destructive piercing-sucking herbivores, infesting more than 1100 plant species, including numerous greenhouse and open-field crops of significant economic importance. Its prolific fecundity and short life cycle contribute to the development of resistance to pesticides. However, effective resistance loci in plants are still unknown. To advance research on plant-mite interactions and identify genes contributing to plant immunity against TSSM, efficient methods are required to screen large, genetically diverse populations. In this study, we propose an analytical pipeline utilizing high-resolution imaging of infested leaves and an artificial intelligence-based computer program, MITESPOTTER, for the precise analysis of plant susceptibility. Our system accurately identifies and quantifies eggs, feces and damaged areas on leaves without expert intervention. Evaluation of 14 TSSM-infested Arabidopsis thaliana ecotypes originating from diverse global locations revealed significant variations in symptom quantity and distribution across leaf surfaces. This analytical pipeline can be adapted to various pest and host species, facilitating diverse experiments with large specimen numbers, including screening mutagenized plant populations or phenotyping polymorphic plant populations for genetic association studies. We anticipate that such methods will expedite the identification of loci crucial for breeding TSSM-resistant plants.

Genes ScBx1 and ScIgl-Competitors or Cooperators?

Two genes, Bx1 and Igl, both encoding indole-3-glycerol phosphate lyase (IGL), are believed to control the conversion of indole-3-glycerol phosphate (IGP) to indole. The first of these has generally been supposed to be regulated developmentally, being expressed at early stages of plant development with the indole being used in the benzoxazinoid (BX) biosynthesis pathway. In contrast, it has been proposed that the second one is regulated by stresses and that the associated free indole is secreted as a volatile. However, our previous results contradicted this. In the present study, we show that the ScIgl gene takes over the role of ScBx1 at later developmental stages, between the 42nd and 70th days after germination. In the majority of plants with silenced ScBx1 expression, ScIgl was either expressed at a significantly higher level than ScBx1 or it was the only gene with detectable expression. Therefore, we postulate that the synthesis of indole used in BX biosynthesis in rye is controlled by both ScBx1 and ScIgl, which are both regulated developmentally and by stresses. In silico and in vivo analyses of the promoter sequences further confirmed our hypothesis that the roles and modes of regulation of the ScBx1 and ScIgl genes are similar.