First report of anthracnose on Ophiopogon jaburan caused by Colletotrichum liriopes in China.

Abstract

Ophiopogon jaburan (Liliaceae), named white lilyturf, is widely cultivated as an ornamental plant in south China. During 2017-2019, leaf spots on O. jaburan were observed all year in Zhanjiang, Guangdong, China (N21°9'3"; E110°17'47"). Almost all plants were infected and the disease incidence on affected leaves was about 80% in the field. Initially, spots were brown, round or oval, and gradually enlarged to irregular shapes. The color of the spots changed from rusty-brown to grayish-white with rusty-brown borders. Subsequently, the spots expanded until the leaves withered and died. Infected tissues were surface-sterilized with 75% ethanol for 30s followed by 1% NaClO solution for 1 min, then rinsed thrice with sterile water, before placed on potato dextrose agar (PDA) containing 50mg/L ampicillin, and incubated in darkness at 25℃ with 90% relative humidity. Colonies growing on PDA were cushion-like, pale greenish grey to grayish black on the front side and clearly dark gray on the reverse. Colony diameter was av. 86.0 mm (n = 15) grown in the dark at 25 ℃ for 10 days. Conidia with oil droplets were colorless, hyaline, smooth-walled, aseptate, slightly curved, and tapered gradually to each end, 12.3-28.9 × 2.2-6.6 μm (av. 20.9×4.2μm, n=200). Setae were brown to dark brown, 2-4 septate, with the base slightly inflated, and measured 40.0-130.3 × 2.2-5μm (av. 84.3 × 3.3μm, n=23). On PDA, scattered or loosely clustered appressoria were elliptical or irregular, smooth-walled, aseptate, and dark brown. To confirm the identification, partial regions of the internal transcribed spacer (White et al. 1990), beta-tubulin (Aveskamp et al. 2009) and actin (Carbone et al 1999) were amplified and sequenced (MW989743, MZ014461 and MZ014462). The blast results showed these sequences had >99.59% homology with sequences of Colletotrichum liriopes holotype strain CBS 119444 (NR_111449, GU228098 and GU227902). Maximum likelihood analysis and Bayesian inference were performed from concatenated sequences using RAxML v.1.0.0 and MrBayes v.3.2.1 software respectively. Several C. liriopes strains clustered in the same clade. Based on morphological-molecular characteristics, the fungus was identified as C. liriopes (Damm et al 2009; Chen et al. 2019). To confirm pathogenicity, healthy leaves were surface disinfected with 75% ethanol and rinsed thrice with sterile water. On ten leaves, three sites were wounded by pricking with needles, and inoculated 20 μL of 106 conidia/ml suspension or mycelium in contact with blade surface using 6-mm mycelial plugs. Similarly, the inoculation was done for three unwounded sites each leaf. Sterile water and medium plugs (without fungus) served as controls. All leaves were incubated on sterile wet filter paper at 25-28℃ with 90% relative humidity. After 7 days, all the inoculated leaves showed symptoms similar to those of field diseases, whereas control leaves remained healthy. The fungus with morphological-molecular features identical to the original isolate was reisolated from the disease lesions. C. liriopes causes anthracnose on Bletilla ochracea, Eria coronaria, Hemerocallis fulva, Pleione bulbocodioides (Jayawardena et al 2016) and Liriope sp. (Yang et al 2020; Chen et al 2019) in China. This is the first report of C. liriopes causing anthracnose on O. jaburan in China. Anthracnose could greatly affect ornamental value of O. jaburan, and this work can alert gardeners to prevent and control of the disease.