A common bean truncated CRINKLY4 kinase controls gene-for-gene resistance to the fungus Colletotrichum lindemuthianum

Identifying the molecular basis of resistance is critical to promote chemical free cropping system. In plants, NLR constitute the largest family of disease resistance (R) genes but they can be rapidly overcome, prompting research of alternative source of resistance. Anthracnose, caused by the fungus Colletotrichum lindemuthianum, is one of the most important diseases of common bean. This study aimed to identify the molecular basis of Co-x, an anthracnose R-gene conferring total resistance to the extremely virulent C. lindemuthianum strain 100. To that end, we sequenced the Co-x 58kb target region in the resistant JaloEEP558 (Co-x) and identified KTR2/3, an additional gene encoding a truncated and chimeric CRINKLY4 kinase, located within a CRINKLY4 kinase cluster. KTR2/3 presence is strictly correlated with resistance to strain 100 in a diversity panel of common beans. Furthermore, KTR2/3 expression is upregulated 24 hours post-inoculation and its transient expression using Agrobacterium-transformation in susceptible genotype increases resistance to strain 100. Altogether, our results provide molecular evidence that Co-x encodes a truncated and chimeric CRINKLY4 kinase probably resulting from an unequal recombination event that occurred recently in the Andean domesticated gene pool. This atypical R-gene might act as a decoy involved in indirect recognition of a fungal effector.