First Report of Colletotrichum fructicola Causing Anthracnose on Indian Jujube (Ziziphus mauritiana) in Taiwan.

Abstract

Ziziphus mauritiana Lamarck known as Indian jujube is one of the most popular and delicious fruit crops in Taiwan. This crop is mainly planted in southern Taiwan and their fruit are harvested for providing fresh fruit. In March 2015, an anthracnose-like disease was observed on Indian jujube fruit (cv. Candied date) planted in an orchard in Yanchao District (22°46'33" N, 120°21'37" E) in Kaohsiung City. The disease was quickly distributed around the orchard after rain and caused great loss (around 40% of fruit infected). The diseased fruit would completely rot and lose its market value. Symptoms could be observed on all the developmental stages of fruit. On ripe fruit, symptoms were round, brown, water-soaked lesions covered with salmon-colored spore masses. Four fungal isolates from diseased fruit in the same orchard were collected by single spore isolation with hand-made glass needle. They were grown on potato dextrose agar (PDA) at 24 to 28°C with diffused light. All four strains produced white to gray, aerial, and cottony mycelia scattered with abundant salmon-colored conidial mass on the center of the colony on PDA. The conidia were hyaline, single celled, round cylindrical on both ends, thin walled, and the contents guttulate. The sizes of conidia were 15.2 (17.5 to 13.0) × 5.0 (5.5 to 4.5) μm (length/width ratio = 3.03, n = 40). DNA was isolated from JC1 and used for amplification of partial sequences of the internal transcribed spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), actin (ACT), β-tubulin 2 (TUB2), chitin synthase 1 (CHS-1), manganese-superoxide dismutase (SOD2) and the intergenic region of apn2 and MAT1-2-1 gene (ApMat) genes (Silva et al. 2012; Weir et al. 2012). A BLAST search against the NCBI database revealed that JC1 gene sequences [GenBank accession nos. MT197188 (ITS), MT199871 (GAPDH), MT199872 (ACT), MT199870 (TUB2), MT815918 (CHS-1), MT815919 (SOD2) and MT221653 (ApMat)] displayed 100.0, 100.0, 99.1, 100.0, 99.7, 99.5 and 99.8% nucleotide identity to the respective gene sequences of Colletotrichum fructicola ICMP 18581 (JX010165, JX010033, FJ907426, JX010405, JX009866, JX010327, and JQ807838). Conidial suspension (1 × 106 conidia/mL) was prepared from JC1 isolate of C. fructicola and inoculated by spraying onto detached, ripe, healthy, non-wounded and surface-disinfected jujube fruit (cv. Candied date, n = 4). Four control fruit were sprayed with sterile water. Fruit were kept in a moist chamber (greater than 90% relative humidity, 24 to 28°C) for 24 h and maintained in the lab for additional 5 days. The inoculated fruit initially showed small light-colored spots in 5 to 7 days, which eventually developed into brown, sunken, water-soaked lesions 8 to10 days after inoculation, similar to the symptoms in the orchard. C. fructicola was re-isolated from symptomatic fruit showing similar morphological characteristics to those collected from the field, thus fulfilling Koch's postulates. No symptom was observed on fruit treated with water and no pathogen was re-isolated. The experiment was performed twice. The JC1 isolate of C. fructicola with the identification number BCRC FU31437 has been deposited at Taiwan Bioresource Collection and Research Center. This pathogen has been found in many plant species in various countries (Weir et al. 2012). To our knowledge, this is the first report of C. fructicola causing Indian jujube fruit anthracnose in Taiwan and worldwide.