First Report of Fusarium tricinctum Causing Stem and Root Rot on Lanzhou Lily (Lilium davidii var. unicolor) in China.

Abstract

Lanzhou lily (Lilium davidii var. unicolor Cotton) is an important bulb edible crop which mostly distributes in middle area of Gansu Province in China (2). Recently, plants of Lanzhou lily developed symptoms of severe wilting. In early autumn of 2012 to 2013, a survey of Lanzhou lily disease was carried out in Yuanjiawan, Caoyuan, Xiguoyuan, and Hutan villages of Lanzhou City and Xuding and Guanshan villages of Linxia Prefecture. Disease symptoms included stem and root rot, vessels showed a brown to dark brown discoloration, plus a progressive yellowing and wilting of leaves from the base. Small pieces of symptomatic leaves, stems, and roots were surface disinfected with 75% ethanol for 30 s, 3% sodium hypochlorite for 5 min, and then washed three times in sterile distilled water. The tissues were placed on Martin Agar at 25°C for 7 days. Three isolates were consistently isolated from diseased tissues and all isolates with morphology similar to Fusarium spp. Isolates were transferred to potato dextrose agar (PDA) and carnation leaf agar (CLA) and incubated at 25°C in darkness. These isolates grew rapidly on PDA and formed abundant dense aerial mycelium, initially white, that became deep pink with age and formed red pigments in the medium. On CLA, macroconidia with 3 to 5 septa were abundant, relatively slender, and curved to lunate. Microconidia were abundant, oval and 0 to 1 septa. Chlamydospores were globose with a smooth outer wall in chains. The rDNA internal transcribed spacer (ITS) region comprising ITS1, ITS2, and 5.8S rDNA was amplified using primers ITS-1 and ITS-4 (3) and sequenced. On the basis of a comparison of 563 bp, all the three isolates had the identical sequence (GenBank Accession No. KF728675). BLASTn analysis of the sequence showed 100% match with the ITS sequences of those F. tricinctum sequences in GenBank (Accession Nos. FJ233196, AY188923, and JF776663). Pathogenicity test was performed by transplanting 2-month-old tissue culture seedlings to plastic pots in a sterile mixture of vermiculite and torf substrate at 1:3 (v/v). Seedlings were inoculated with 6 ml of the conidial suspension (104 conidia/ml) on the roots of plant in each pot, three plants per pot, and three replicates for each treatment. Seedlings treated with sterile water served as controls. The seedlings were placed in a plant growth chamber maintained at 22 ± 3°C, relative humidity >70%, 16 h light per day, and irrigated with sterile water. After 4 weeks, inoculated plants exhibited wilting foliage that with symptoms similar to those observed in the field, while the control plants remained healthy. F. tricinctum was re-isolated from all inoculated plants. The disease has been reported previously in ornamental lily in China (1). However, to the best of our knowledge, this is the first report of F. tricinctum causing wilt on edible Lanzhou lily in China and the disease must be taken into consideration of current disease management. This work supported by NSFC No. 31370447 and Hundred Talents Program of CAS "Molecular mechanism of biological control on plant diseases."