Identification of Pathogenic Fusarium spp. Responsible for Root Rot of Angelica sinensis and Characterization of Their Biological Enemies in Dingxi, China.

Root rot is a serious disease in plantations of Angelica sinensis, severely reducing yield and quality and threatening sustainable production. Fusarium isolates (n = 32) were obtained from field samples of root rot tissue, leaves, and infected soil. Isolates were identified by comparison of the sequences of their internal transcribed spacer region and translation elongation factor 1-α to sequences of known species in the National Center for Biotechnology Information database. These Fusarium isolates include Fusarium tricinctum (43.75%), F. equiseti (31.25%), F. solani (9.37%), F. oxysporum (6.25%), F. acuminatum (6.25%), and F. incarnatum (3.12%). For pathogenicity testing under greenhouse conditions, seven isolates were selected based on a phylogenetic analysis, including four strains of F. tricinctum and one strain each of F. solani, F. oxysporum, and F. acuminatum. The seven isolates were all pathogenic but differed in their ability to infect: The four F. tricinctum strains were capable of causing root rot in A. sinensis at 100% incidence and were highly aggressive. Furthermore, the symptoms of root rot induced by those seven isolates were consistent with typical root rot cases in the field, but their disease severity varied. Observed histopathological preparations of F. tricinctum-infected seedlings and tissue slide results showed that this fungal species can penetrate epidermal cells and colonize the cortical cells where it induces necrosis and severe plasmolysis. Plate confrontation experiments showed that isolated rhizosphere bacteria inhibited the Fusarium pathogens that cause root rot in A. sinensis. Our results provide timely information about the use of biocontrol agents for suppression of root rot disease.

Allelochemicals from the Rhizosphere Soil of Potato (Solanum tuberosum L.) and Their Interactions with the Soilborne Pathogens.

To reveal the allelopathic effects of potato, seven compounds were isolated from the rhizosphere soil: 7-methoxycoumarin (1), palmitic acid (2), caffeic acid (3), chlorogenic acid (4), quercetin dehydrate (5), quercitrin (6), and rutin (7). Bioassays showed that compounds 1, 2, 4, and 6 had inhibitory effects on the growth of L. sativa and tissue culture seedlings of potato. The existence of the allelochemicals was confirmed by HPLC, and their contents were quantified with a total concentration of 9.02 µg/g in the rhizosphere soil of replanted potato. Approaches on the interactions of the allelochemicals and pathogens of potato including A. solani, B. cinerea, F. solani, F. oxysporum, C. coccodes, and V. dahlia revealed that compound 1 had inhibitory effects but compounds 2-4 promoted the colony growth of the pathogens. These findings demonstrated that the autotoxic allelopathy and enhancement of the pathogens caused by the accumulation of the allelochemicals in the continuously cropped soil should be one of the main reasons for the replant problems of potato.

[Effects of plastic film mulching on soil quality, growth of Angelica sinensis, and weed occurrence in cold and humid areas]. / è¦†è†œå¯¹é«˜å¯’é˜´æ¹¿åŒºå½“å½’åœŸå£¤è´¨é‡ã€æ¤æ ªç”Ÿé•¿å’Œæ‚è‰å‘ç”Ÿçš„å½±å“.

We analyzed the growth dynamic and bolting rate of Angelica sinensis, soil quality and enzyme activities and weed density and control effect in a field experiment under different mulching patterns, to provide theoretical basis for the application of plastic film in genuine producing area of A. sinensis. The planting patterns were conducted as hole seeding under ridging with plastic-film mulching (LS), trenching and slant planting under film-side cultivation (MC) and trenching and slant planting in open field (LD). Our results showed that, 1) compared with LD, soil organic matter content in top layer under the treatments of LS and MC was increased by 4.4% and 14.3%, respectively, with that under MC being statistically significant. Soil bulk density was significantly decreased by 11.6% and 8.5%, while pH was significantly decreased by 4.6% and 1.7%. The activities of soil sucrase, phosphatase and urease were significantly increased by the two mulching methods, but that of catalase was inhibited to a certain extent. 2) Mulching film improved the speed of returning green after transplanting, the early bolting rate, and the individual medicinal quality of A. sinensis. MC showed the fastest, the most uniform, and the highest greening rate. LS bolting rate was the highest, and the fresh mass of MC and LS was significantly increased by 20.4% and 58.4%, respectively. 3) Weed density under the treatment of MC and LS was significantly reduced by 34.0% and 25.8%. Compared with LS, MC significantly increased the control effect of plant and fresh mass by 21.7% and 63.4%, respectively. In conclusion, film cultivation methods could improve the environment for root growth, reduce weed density, improve weed control effect, and promote growth process and substance accumulation, but could promote the bolting of A. sinensis in early phase.