Identification of Bletilla striata rust pathogen and resistance resources screening

Abstract

In order to identify the pathogen that caused rust of Bletilla striata in Guangxi Zhuang Autonomous Region and to screen resistance resources for B. striata, the rust pathogen was isolated from infected leaves of B. striata and identified using morphology and molecular methods. At the same time, the resistance of 23 B. striata from different regions was evaluated by artificial inoculation of pathogen. The results were as follows: (1) The urediopores of strain X2 isolated from diseased leaves in B. striata were golden yellow, oval, (21.43-30.95) μm × (13.10-19.05) μm. The teleutospores were golden yellow, obovate or clavate, (17.25-30) μm × (5.5-6.65) μm. (2) The length of ITS sequence of strain X2(OQ826009) was 689 bp, which were compared with other ITS sequences in the GenBank, and the similarity reached 95.86% compared with Coleosporium sp. (KY783686.1). But the phylogenetic tree showed that the sequence was clustered together with two sequences of Coleosporium bletiae (MN108161.1, OP363680.1). The strain X2 was identified as Coleosporium bletiae by combining morphology and molecular methods. (3) After 14 days of artificial inoculation with strain X2, the disease index of 23 Bletilla striata ranged from 0 to 70.7. And the resistance of strain X2 from 23 B. striata were divided into six different levels according to the disease index. Among them, one immune materials was identified for the disease index was 0. Four highly resistant materials were identified for the disease index was 1.7-4.7. Six disease-resistant materials were identified for the disease index was 5.6-9.4. Five medium-resistant materials were identified for the disease index was 12.7-18.3. Five susceptible materials were identified for the disease index was 32.0-49.1 and two highly susceptible materials were identified for the disease index was 62.2-70.7. In conclusion, five materials (one immune material and four highly resistant materials) of B. striata from different places (Honghe City in Yunnan Province, Gongcheng County and Baise City in Guangxi Zhuang Autonomous Region, Zunyi City in Guizhou Province and Yichang City in Hubei Province, respectively) can be promoted directly or applied as parent materials for creating excellent germplasm to resist the rust in B. striata for they express immune or highly resistance. This study provides the basis for further research on pathogenesis and control of rust in B. striata.

Keywords

• bletilla striata
• rust
• pathogen identification
• coleosporium sp.
• resistance resource