Evaluating strawberry resistance and the early transcriptional responses of cinnamyl alcohol dehydrogenase genes to three pathogens
Strawberry is susceptible to destructive pathogens including Colletotrichum siamense ( Cs ), Fusarium oxysporum f.sp. fragariae ( Fof ) and Xanthomonas fragariae ( Xf ). There lacks a system including pathogens, uniform grading scales and candidate genes for assessing strawberry broad-spectrum resistance. The main objectives of current work are to verify representative microbial strains and identify Cinnamyl Alcohol Dehydrogenase ( CAD ) genes in strawberry basal defenses to three leading pathogens. Pathogenic strains were selected and used to study the resistance of three strawberry varieties. Common scales were applied for grading disease severity. Quantitative RT-PCR was performed to study the dynamic transcriptional profiles of CAD s in early responses to three pathogens in all varieties. Pathogenic Cs , Fof and Xf isolates from strawberry crown parts were used for non-wound spraying inoculation on whole plants. F. vesca ‘Hawaii4’ was most susceptible to Fof and Xf . The cultivar ‘Benihoppe’ was most susceptible to Cs . Cultivar ‘Shenyi’ was less susceptible than ‘Benihoppe’, exhibiting a broad-spectrum resistance to Cs and Xf . ELI3 -like CAD s were down-regulated in ‘Hawaii4’ just 5 min post Cs inoculation but subsequently up-regulated at 30 min. Upon inoculation with Cs and Fof , six CADs displayed largely similar transcription profiles in ‘Shenyi’, while more CAD members were provoked in susceptible ‘Benihoppe’. The early expression profiles of strawberry CAD s were largely host-genotype specific, but not pathogen-specific. Representative strains of C. siamense , F. oxysporum f.sp. fragariae and X. fragariae were verified and successfully used to assess strawberry broad-spectrum resistance integrated with a common set of grading scales for disease severity. Transcriptional responses of CAD s in strawberry leaves occurred as early as 5 min post Cs inoculation. Several CAD s including CAD4 , − 9 , − 11 and − 12 might function as early markers of strawberry basal resistance to broad-spectrum pathogens.