| A survey on diseases of ten kinds of precious trees in guangxi were done, and study on the biological characteristics of Corynespora cassiicola and Curvularia lunata, the pathogens of Tectona grandis leaf spots. The results were as follows:1. Seventeen new diseases were foundTwenty-eight diseases were identified after a survey on diseases of ten kinds of precious trees in guangxi, among which seventeen new diseases were found, they were Erythrophleum fordii brown spot (Alternaria arborescen), Erythrophleum fordii Phomopsis brown spot(Phomopsis sp.), and Erythrophleum fordii algal spot (Cephaleuros virescens), Bischofia javanica red spot (Pestalotiopsis microspora), and Bischofia javanica gray mold (Botrytis cinerea), Castanopsis hystrix red spot (Pilidella granati), Castanopsis hystrix brown spot (Pestalotiopsis pauciseta), and Castanopsis hystrix anthracnose (Colletotrichum gloeosporioides), Michelia macclurei black spot (Alternaria alternata), Podocarpus macrophyllus leaf tip blight(Pestalotiopsis virgatula), and Podocarpus macrophyllus leaf blight (Alternaria alternata), Phoebe bournei brown spot (Pestalotiopsis gracilis), Podocarpus nagi leaf tip blight (Pestalotiopsis longisetula), and Podocarpus nagi leaf blotch (Alternaria tenuissima), Tectona grandis anthracnose (Colletotrichum gloeosporioides), Tectona grandis Curvularia leaf spot (Curvularia lunata), and Tectona grandis Corynespora leaf spot (Corynespora cassiicola).2. Biological characteristics of pathogens of Tectona grandis Curvularia leaf spot and Tectona grandis Corynespora leaf spot (Corynespora cassiicola).The examination results of the biological characteristics of the pathogen of Tectona grandis Curvularia leaf spot were as the following:The range of temperature for mycelia growth of C. lunata was 10℃-40℃ and the optimum temperature was 27.5℃-30℃; for the sporulation, the range of temperature was 15℃-35℃ and the optimum temperature was 35℃; for the conidial germination, the range of temperature was 10℃-45℃ and the optimum temperature was 35℃. Whether lighting or not had little effect on the mycelia growth of C. lunata, but the effect on its sporulation was obvious, that was 24h darkness in a day could promote the sporulation of C. lunata, but 12h alternating light and darkness was not suitable for its sporulation. The range of pH for the mycelia growth of C. lunata was 2-12, the optimum pH was 5-10 and the range of pH for the conidial germination of C. lunata was 5-7, the optimum pH was 5. The lethal temperature for the mycelia was 54℃ in 20min, and the lethal temperature for the conidial was 49℃ in 20min. PDA medium and PSA medium were suitable for the mycelia growth and sporulation of C. lunata, respectively, but Czapek medium was not both conducive to the mycelia growth and sporulation. Maltose and potassium nitrate were the optimum carbon source and nitrogen source. The suppressive effect of Prochloraz on C. lunata was significant, but the suppressive effect carbendazim-thiram-Xin Junan of on C. lunata was worst.The examination results of the biological characteristics of the pathogen of Tectona grandis Corynespora leaf spot as the following:For the mycelia growth and the sporulation of C. cassiicola, the range of temperature respectively were 5℃-40℃ and 10℃-35℃, and the optimum temperature were both 27.5℃. For the conidial germination, the range of temperature was 5℃-42.5℃ and the optimum temperature was 30℃. For the mycelia growth and the sporulation of C. cassiicola,24h darkness could promote the mycelia growth and the sporulation of C. cassiicola, but 12h alternating light and darkness suppressed its mycelia growth and sporulation. The range of pH for the mycelia growth of C. cassiicola was 5-11, the optimum pH was 10. The range of pH for the conidial germination of C. cassiicola was 4-10, the optimum pH was7. The lethal temperature for the mycelia and the conidial were both of 50℃ in 20 min. PDA medium was both suitable for the mycelia growth and sporulation of C. cassiicola, but PSA medium and COA medium were not conducive to the mycelia growth and sporulation, respectively. Dextrose and ammonium nitrate were the optimum carbon source and nitrogen source for the mycelia growth of C. cassiicola, but ammonium sulfate and lactose were worst carbon source and nitrogen source, respectively. The suppressive effect of carbendazim on C. cassiicola was significant, but the suppressive effect of dithane Zn-78 on C. cassiicola was worst. |
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