First Report of <i>Colletotrichum fructicola</i> Causing Fruit Rot in <i>Psidium guajava</i> in China

Guava (Psidium guajava) is a tropical fruit crop native to the Americas and is widely cultivated in tropical and subtropical regions, including several provinces in China such as Guangdong, Guangxi, Sichuan, and Yunnan. In October 2025, a severe postharvest fruit anthracnose was found in Yulin City (22°37' N, 110°9' E), Guangxi, China, with a disease incidence ranging from 33% to 68%. The fruits exhibited typical anthracnose symptoms: initially, brown, irregular, water-soaked lesions developed on the surface, which later expanded into concentric rings with abundant black acervuli. In severe cases, lesions produced prominent salmon-pink conidial masses. A total of 37 symptomatic fruits were randomly collected from six commercial orchards. Using single-spore isolation (Choi et al. 1999), eight isolates were obtained and exhibited similar morphological characteristics. On PDA, colonies were circular, white, cottony, with yellowish-brown discoloration after 5 days. Conidia were hyaline, aseptate, cylindrical to oval, measuring 7.37 to 19.42 × 3.39 to 5.44 µm (n = 50). The appressoria were brown to dark brown, nearly ovoid to cylindrical, and slightly irregular, measuring 6.42 to 12.65 μm × 5.23 to 8.48 μm (n=50). Morphological characteristics were consistent with those described for the C. gloeosporioides species complex (Weir et al. 2012). For molecular identification, ITS (White et al. 1990), TUB2 (Glass and Donaldson 1995), GAPDH (Templeton et al. 1992), CHS-1, ACT, HIS3 (Carbone and Kohn 1999), GS, APN2, APN2/MAT-IGS, and GAP2-IGS (Vieira et al. 2020) genes were amplified via PCR using previously described primers, and the sequences were deposited in GenBank (ITS: PX760247, PX760248; ACT: PX761360, PX761361; CHS-1: PX761362, PX761363; GAPDH: PX761364, PX761365; HIS3: PX761366, PX761367; TUB2: PX761368, PX761369; GS: PX761370, PX761371; APN2/MAT-IGS: PX761372, PX761373; APN2: PX761374, PX761375; GAP2-IGS: PX761376, PX761377). Multilocus phylogenetic trees were constructed with both Maximum Likelihood (ML) and Maximum Parsimony (MP) methods. The two representative isolates clustered robustly within the C. fructicola reference (ICMP 18581), with strong bootstrap support (ML/MP: 96%/100%), and were clearly distinguished from other species. Pathogenicity tests were performed using isolate FSLTJ01. Conidia were collected and resuspended in sterilized distilled water (1×106 conidia/mL). Three surface-disinfected, healthy guava fruits were used per replicate, and three independent replicates were performed. In each replicate, fruits were inoculated with 30 µL of the conidial suspension, while the control fruits were inoculated with 30 μL of sterile water. Inoculated fruits were initially kept in a humid chamber at 25°C and 80% relaive humidity for 24 h in darkness, and then transferred to normal laboratory conditions (25°C, 12 h photoperiod) for an additional 4 days. Typical anthracnose symptoms, identical to those observed in the field, developed at all inoculation sites within 5 days, progressing to fruit rot. No symptoms were observed on control fruits. The re-isolated strains had the same morphological characteristics and sequences as the original isolates, and no isolates were obtained from the control. Thus, the Koch’s postulates were fulfilled. Colletotrichum fructicola has been previously reported as a causal agent of guava anthracnose in Brazil (Soares et al. 2024). To our knowledge, this is the first report of C. fructicola causing fruit anthracnose on guava in China. This report provides evidence to raise awareness among growers about anthracnose disease of P. guajava in order to develop effective disease control strategies.