Occurrence of the Stem End Rot Disease in Pomelo, Citrus maxima Caused by Lasiodiplodia Species in Ben Tre Province, Vietnam

The study was conducted to isolate and select the fungal isolates causing stem end rot of pomelo fruit and characterized by strong growth. Pomelos showing signs of stem end rot or stem wilt were collected. Sixteen fungal isolates were isolated from fruit samples collected from two districts Binh Dai and Mo Cay Bac of the Ben Tre province, Vietnam. The experiment with 16 fungal isolates was completely randomized, with 3 replicates, each replicate being a Petri dish. Nine fast growing fungal isolates were selected, with the diameter of fungal colonies ranging from 8.60 to 9.00 cm, 48 h after inoculation. These nine isolates when inoculated to Pomelo fruits caused pomelo fruit rot symptoms and their pathogenicity was confirmed following Koch’s postulates. The range of infection diameter on pomelo fruits was 0.85-3.00 cm. The three fungal isolates causing the earliest and the most severe pomelo fruit rot were identified as Lasiodiplodia pseudotheobromae PL-M01-A4-B and PL-B01-A7-B, and L. theobromae PL-M01-A6-B by sequencing the ITS region, with 100% similarity. Keywords: Fruit rot, Lasiodiplodia pseudotheobromae, Lasiodiplodia theobromae, pomelo, pathogenic factor, stem end rot.