Isolation and pathogenicity evaluation of Phytophthora colocasiae causing leaf blight disease in taro (Colocasia esculenta L. Schott) in some Northern provinces, Vietnam

The study aimed to isolate and purify the pathogenic fungal strains isolated from blight disease taro leaves in some provinces of Northern Vietnam, from which to select the pathogenic strains belonging to Phytophthora colocasiae species, and to determine their toxicity on taro plants. From leaf tissue showing leaf blight collected from taro fields in 6 places in Bac Giang, Bac Ninh, Hanoi, and Hoa Binh provinces, 6 strains of the fungus were isolated. Based on the morphological characteristics as well as ITS rDNA sequences, it was confirmed that two of the six strains were Phytophthora colocasiae and named BN1 and SB, respectively. The sporangium of strain BN1 was ovoid and strain SB was a semi-papillary spherical shape. Both fungal strains grew well on CGA and PGA media and had equivalent toxicity through in vitro infection testing on 3 taro gene sources.