Unraveling Psa resistance in kiwifruit: insights from A. chinensis and A. arguta gene expression

Kiwifruit (Actinidia spp.) cultivation has been severely impacted by bacterial canker caused by Pseudomonas syringae pv. actinidiae (Psa), especially in susceptible species like A. chinensis. This study investigates the molecular responses to Psa infection in two genotypes, the susceptible ‘Soreli’ (A. chinensis var. chinensis) and potentially resistant ‘Cornell’ (A. arguta). Canes were inoculated with Psa and kept under controlled conditions for six weeks, with disease severity assessed through lesion length and infection percentage. RNA sequencing (RNA-seq) was performed on sub-cortical tissues to identify differentially expressed genes (DEGs) linked to resistance and susceptibility. Module-specific analyses revealed that Modules 1 and 2 were enriched for DEGs distinguishing the two genotypes, possibly reflecting intrinsic genetic differences. Module 3, however, was enriched for DEGs in both genotypes under Psa infection, indicating its involvement in the plant’s response to the bacteria. QTL analysis identified three QTLs associated with resistance in A. arguta and one linked to susceptibility in A. chinensis. Notably, QTLs on chromosomes 4, 17, and 28 were associated with resistance mechanisms, while a QTL on chromosome 9 was linked to susceptibility, involving genes related to redox signaling and cuticular wax biosynthesis. These findings provide valuable insights into the genetic basis of Psa resistance and susceptibility in kiwifruit, offering potential targets for future breeding efforts.