Correlation analysis between continuous cropping obstacle of Gastrodia elata and Ilyonectria fungi and relieving strategy / 中国中药杂志

The continuous cropping obstacle of Gastrodia elata is outstanding, but its mechanism is still unclear. In this study, microbial changes in soils after G. elata planting were investigated to explore the mechanism correlated with continuous cropping obstacle. The changes of species and abundance of fungi and bacteria in soils planted with G. elata after 1, 2, and 3 years were compared. The pathogenic fungi that might cause continuous cropping diseases of G. elata were isolated. Finally, the prevention and control measures of soil-borne fungal diseases of G. elata were investigated with the rotation planting pattern of "G. elata-Phallus impudicus". The results showed that G. elata planting resulted in the decrease in bacterial and fungal community stability and the increase in harmful fungus species and abundance in soils. This change was most obvious in the second year after G. elata planting, and the soil microbial community structure could not return to the normal level even if it was left idle for another two years. After G. elata planting in soils, the most significant change was observed in Ilyonectria cyclaminicola. The richness of the Ilyonectria fungus in soils was significantly positively correlated with the incidence of G. elata diseases. When I. cyclaminicola was inoculated in the sterile soil, the rot rate of G. elata was also significantly increased. After planting one crop of G. elata and one to three crops of P. impudicus, the fungus community structure in soils gradually recovered, and the abundance of I. cyclaminicola decreased year by year. Furthermore, the disease rate of G. elata decreased. The results showed that the cultivation of G. elata made the Ilyonectria fungi the dominant flora in soils, and I. cyclaminicola served as the main pathogen of continuous cropping diseases of G. elata, which could be reduced by rotation planting with P. impudicus.

Resistance of different ecotypes of Gastrodia elata to tuber rot / 中国中药杂志

Tuber rot has become a serious problem in the large-scale cultivation of Gastrodia elata. In this study, we compared the resistance of different ecotypes of G. elata to tuber rot by field experiments on the basis of the investigation of G. elata diseases. The histological observation and transcriptome analysis were conducted to reveal the resistance differences and the underlying mechanisms among different ecotypes. In the field, G. elata f. glauca had the highest incidence of tuber rot, followed by G. elata f. viridis, and G. elata f. elata and G. elata f. glauca×G. elata f. elata showed the lowest incidence. Tuber rot showcased obvious plant source specificity and mainly occurred in the buds and bottom of G. elata plants. After infection, the pathogen spread hyphae in host cortex cells, which can change the endophytic fungal community structure in the cortex and parenchyma of G. elata. G. elata f. glauca had thinner lytic layer and more sugar lumps in the parenchyma than G. elata f. elata. The transcription of genes involved in immune defense, enzyme synthesis, polysaccharide synthesis, carbohydrate transport and metabolism, hydroxylase activity, and aromatic compound synthesis had significant differences between G. elata f. glauca and G. elata f. elata. These findings suggested that the differences in resis-tance to tuber rot among different ecotypes of G. elata may be related to the varied gene expression patterns and secondary metabolites. This study provides basic data for the prevention and control of tuber rot and the improvement of planting technology for G. elata.

Investigation, analysis and identification of disease of Gastrodia elata f. glauca / 中国中药杂志

Fungal disease is an important factor restricting the healthy development of Gastrodia elata industry. The control of fungal disease in G. elata is an important issue in production. This paper makes a detailed investigation on the current situation of G. elata disease in China through statistics on the failure rate, rotten pit rate and occurrence rate of G. elata disease in the main producing areas of China. It was found that G. elata disease was mainly infected from the top bud and junction, causing the occurrence rate of disease was 6%-17%, and the yield decreased by 10%-30%. The 23 dominant fungi were isolated from 18 typical G. elata disease samples. Through identification of colony morphology, mycelium morphology, spore morphology and genetic characteristics, they were finally identified as 13 species, belonging to 7 families and 7 genera. Trichoderma harzianum, Ilyonectria sp. and Ilyonectria destructans are the most frequently separated. Their isolation frequency were 22.22%,16.67%,16.67% respectively. Ilyonectria sp. and I. destructans were the first time isolated from G. elata disease samples. They may be the main pathogens causing soil-borne diseases of G. elata. T. harzianum has certain potential as Gastrodia biocontrol bacteria. This study can provide a theoretical basis for the research and development of control technology of Gastrodia fungi disease.

Effect of Gastrodiae elata-Phallus impudicus sequential planting pattern on soil microbial community structure / 中国中药杂志

Gastrodia elata is a heterotrophic plant that needed to be symbiotic with Armillaria. The obstacle of continuous cropping in G. elata is serious during the G. elata cultivation, and the mechanism of obstacle in G. elata continuous cropping had not been solved. The planting of G. elata-Phallus impudicus is a new sequential planting pattern adopted in Guizhou province, but the effect of the cultivation on soil microbial community structure is still unclear. In this study, we collected four soil samples for the research including the soil without planted G. elata as control(CK), rhizosphere soil samples tightly adhering to the G. elata surface(GE), rhizosphere soil samples tightly adhering to Armillaria which was symbiotic with G. elata(AGE), the rhizosphere soil of P. impudicus planting after G. elata cultivation(PI). In order to explore the mechanism, the research study on the soil of G. elata-P. impudicus by using ITS and 16 S rDNA high-throughput sequencing technologies to detect soil microbial community structure including fungi and bacteria in the soil of CK, AGE, GE and PI. OTU clustering and PCA analysis of soil samples showed that the soil microbial diversity was relatively similar in AGE and GE. And the soil microbial in PI and CK clustered together. The results showed that AGE and GE had similar soil microbial diversity, as well as PI and CK. Compared with CK, the soil microbial diversity and abundance in AGE and GE were significantly increased. But the microbial diversity and abundance decreased in PI compared with AGE and GE. The annotation indicated that the abundance of Basidiomycota, Acidobacteria and Chloroflexi decreased, and that of Ascomycota, Zygomycota and Proteobacteria increased in AGE and GE compared with CK. In contrast to AGE and GE, PI was the opposite. The abundance of Basidiomycota, Acidobacteria and Chloroflexi increased in PI compared with AGE and GE. The abundance of microorganisms in the soil of PI and CK was similar. In addition, the co-culture of Armillaria and P. impudicus indicated that P. impudicus had obvious antagonistic effects on the growth of Armillaria. Therefore, it is speculated that the mechanism of G. elata-P. impudicus planting pattern related to the change of soil microbial. And we supposed that P. impudicus might inhibit the growth of Armillaria and change the soil microbial community structure and the abundance of soil microbial. And the soil microbial community structure was restored to a state close to that of uncultivated G. elata. Thus, the structure of soil microbial community planting G. elata could be restored by P. impudicus planting.

Identification of four Armillaria strains and their effects on quality and yield of Gastrodia elata f. glauca / 中国中药杂志

In order to improve the quality and yield of Gastrodia elata f. glauca,determine the suitable Armillaria strains for the accompanying experiment in Xiaocaoba,Yiliang,four Armillaria strains were selected. They were used for G. elata cultivation,and the gene sequence,r DNA-ITS,β-tubulin and EF1-α of four Armillaria strains,were compared and analyzed. The yield was mesured in November which was based on previous laboratory research. The tubers were washed and steamed,then dried and powdered. The content of gastrodin and p-hydroxybenzyl alcohol was determined by UPLC,the polysaccharide was determined by phenol-concentrated sulfuric acid method. The results showed that the strains M1,M2,M3 and M4 were Armillaria gallica group but there were differences in the yield and active ingredient content when they were cultivated with the same G. elata. The yield of G. elata( Jian Ma) was the lowest when cultivated with Armillaria strain M3,but it was not the same when used M1,0. 981 kg·m-2,the highest yield in the four stains.The content of gastrodin was 0. 581%,the total content of gastrodin and p-hydroxybenzyl alcohol was 0. 595%,when accompanied with M1 strains. It was higher than other strains. The content of G. elata polysaccharide was 2. 132%,which was similar to the content of M3 strain,higher than that of M2 and M4 strain. Selecting phylogenesis of Armillaria strians,the content of active ingredient,and the yield as indicators,it was concluded concerned that the M1 strain was the best of four strains. The results will provide a theoretical basis and guidance for higher yield and quality in cultivation of G. elata in Yiliang.