Endophytic Diaporthe citrichinensis as a new source to alleviate post-harvest fungal infections in apple (Malus x domestica Borkh.)

After harvesting, Apple is susceptible to being attacked by various fungal pathogens, rendering it unconsumable and further reducing its commercial value. To mitigate these losses, biocontrol strategies utilizing endophytic fungi are gaining momentum as effective alternatives to synthetic fungicides. In the present study, 155 endophytic fungi were isolated from various parts of Malus x domestica Borkh., sourced from Mandi (Himachal Pradesh) and Pulwama (Jammu & Kashmir). The isolates were subjected to screening for antifungal activity against the primary post-harvest pathogens of apple including, Alternaria alternata, Aspergillus niger, Botrytis cinerea, Penicillium expansum, Rhizopus sp., and Venturia inaequalis. In the dual-confrontation test, the isolates 03MDLP P3–3 and 01MDLM P1–6 exhibited the highest percentage inhibition against all target phytopathogens. The potent cultures were further scrutinized using sandwich assay, wherein 03MDLP P3–3 exhibited complete growth inhibition against all phytopathogenic fungi, indicating its antifungal efficacy, likely attributed to its capacity to release volatile organic compounds. Using morphological and molecular techniques, 03MDLP P3–3 was identified as Diaporthe citrichinensis. This study marks the first report of isolating D. citrichinensis as an endophyte from apples. Furthermore, a pathogenicity test was conducted on the potent isolate, revealing no harmful effects when introduced to apple fruits according to the Koch's postulate. The effect of D. citrichinensis was also examined under in vivo conditions against the major post-harvest fungal pathogens of apple fruits, revealing that no lesion development was noted on the test fruits inoculated with spore suspension of pathogens in the presence of D. citrichinensis. The present study offers a promising avenue for utilizing D. citrichinensis as a biocontrol agent to combat post-harvest fungal diseases in apple production.