Antifungal effects of three medicinal crops on Phytophthora nicotianae / 中国中药杂志

Tobacco black shank is one of the most harmful soil-borne diseases infected by Phytophthora parasitica. In order to probe the control method to this disease, in this study, the mycelial growth rate method was employed to investigate the antifungal effects of extracts from stem-leaf and root, root exudates, and their combination of Scrophularia ningpoensis, Chuanmingshen violaceum and Pinellia ternata The results showed that: ①Stem-leaf and root extracts of S. ningpoensis, C. violaceum and P. ternata exhibited different antifungal activities, and the inhibition increased with the increase of extract concentration. The antifungal effect of S. ningpoensis extracts at 0.5 g•mL⁻¹ was the strongest than other medicinal plants, the inhibition rate of steam-leaf and root extracts reached 74.88%, 69.27%, respectively. The inhibitory effect of C. violaceum and P. ternata was relatively lower, however, there is a significant gain effect after combination of steam-leaf and root extracts of C. violaceum. ②The root exudates of S. ningpoensis, C. violaceum and P. ternata showed fungistasis to Phytophthora nicotianae, and fungistasis was enhanced with the increase of root exudate concentration. The antifungal effect in the order of C. violaceum > S. ningpoensis > P. ternata. ③The antifungal activity of combination of extract and root exudate from S. ningpoensis was similar with the effect of C. violaceum, they were both stronger than P. ternata, and the antifungal activity for three combination were located between the antifungal activity of their extracts and root exudates. S. ningpoensis and C. violaceum can be potentially applied to prevent and control the tobacco black shank.

Efficacy of Chaetomium Species as Biological Control Agents against Phytophthora nicotianae Root Rot in Citrus

Thailand is one of the largest citrus producers in Southeast Asia. Pathogenic infection by Phytophthora, however, has become one of major impediments to production. This study identified a pathogenic oomycete isolated from rotted roots of pomelo (Citrus maxima) in Thailand as Phytophthora nicotianae by the internal transcribed spacer ribosomal DNA sequence analysis. Then, we examined the in vitro and in vivo effects of Chaetomium globosum, Chaetomium lucknowense, Chaetomium cupreum and their crude extracts as biological control agents in controlling this P. nicotianae strain. Represent as antagonists in biculture test, the tested Chaetomium species inhibited mycelial growth by 50~56% and parasitized the hyphae, resulting in degradation of P. nicotianae mycelia after 30 days. The crude extracts of these Chaetomium species exhibited antifungal activities against mycelial growth of P. nicotianae, with effective doses of 2.6~101.4 microg/mL. Under greenhouse conditions, application of spores and methanol extracts of these Chaetomium species to pomelo seedlings inoculated with P. nicotianae reduced root rot by 66~71% and increased plant weight by 72~85% compared to that in the control. The method of application of antagonistic spores to control the disease was simple and economical, and it may thus be applicable for large-scale, highly effective biological control of this pathogen.

Stem Blight Control of Schizonepeta tenuifolia Caused by Phytophthora nicotianae Using Trichoderma spp / 中草药·英文版

Objective To control stem blight disease of Schizonepeta tenuifolia caused by Phytophthora nicotianae.Methods The antagonist effect of 13 Trichoderma strains(including T.viride and T.hamianum)was evaluated upon mycelia growth of P.nicotianae.Trichoderma strains with high antagonistic activities against the pathogen were used to control stem blight of S.tenuifolia in the field.Results Of 13 Trichoderma strains tested,T.viride strain M3 showed maximum mycelia growth inhibition(83.2%)to the pathogen,followed by T.viride strain Tv04-2(78.2%)and then T.harziamum strain ThB(65.0%),in vitro.Fungal cell wall degrading enzymes,protease,and β-1,3-glueanase were analyzed qualitatively and quantitatively in further study.T.viride strains M3,Tv04-2,and T.harzianum strain ThB efficiently against P.nicotianae were used to control stem blight of S.tenuifolia in the field,and T.viride strain M3 showed the best biocontrol potential.Conclusion Trichoderma spp.can be used as alternatives of pesticides to control stem blight,one of the serious soilhome diseases of S.tenuifolia caused by P.nicotianae.However,though T.viride strains Tv04-2 aad T.harzianum strain ThB are also highly against P.nicotianae in vitro,the controlling efficacy of them on stem blight disease is not as excellent as T.viride strains M3 in the field.