Four New Chromone Derivatives from Colletotrichum gloeosporioides

Four previously unreported chromones, 5‐hydroxy‐2‐(hydroxymethyl)‐8‐methoxy‐4H‐chromen‐4‐one ( 1 ), (5R,7S)‐5,7‐dihydroxy‐2‐propyl‐5,6,7,8‐tetrahydro‐4H‐chromen‐4‐one ( 2 ), (5R,7S)‐5,7‐dihydroxy‐2‐methyl‐5,6,7,8‐tetrahydro‐4H‐chromen‐4‐one ( 3 ), and (5R,7S)‐5,7‐dihydroxy‐2‐[(E)‐prop‐1‐en‐1‐yl]‐5,6,7,8‐tetrahydro‐4H‐chromen‐4‐one ( 4 ), as well as one known analogue 5‐hydroxy‐2‐methyl‐4H‐chromen‐4‐one ( 5 ) were isolated from the fermentation broth of the endophytic fungus Colletotrichum gloeosporioides derived from the mangrove Ceriops tagal. Their structures were elucidated based on extensive spectroscopic analyses. The absolute configurations of 2 – 4 were determined by comparison the experimental and calculated electronic circular dichroism (ECD) spectra. Compound 2 showed cytotoxic activity against A549 cell line with the IC₅₀ value of 0.094 mm .     

Physiological characterisation of Colletotrichum gloeosporioides,the incitant of anthracnose disease of noni in India

Ten isolates of Colletotrichum gloeosporioides were collected from different noni growing areas of Tamil Nadu, Karnataka and Kerala in India and their pathogenicity was proved under glass house conditions. Effect of different pH levels, temperature, light intensity and media were tested against the growth of C. gloeosporioides under in vitro. The results indicated that the growth of C. gloeosporioides was maximum in pH range of 6.50–7.00 and temperature range of 25–30°C. Exposure of the fungus to alternate cycles of 12 h light and 12 h darkness resulted in the maximum mycelial growth of C. gloeosporioides compared to the 24 h exposure to continuous light and 24 h exposure to continuous dark. Among the different media tested, host leaf extract medium supported significantly the maximum growth of all the 10 isolates of C. gloeosporioides followed by potato dextrose agar. Further, the strains were found to vary morphologically between the isolates under the study.     

Assessment of potential antagonists for anthracnose (Colletotrichum gloeosporioides) disease of mango (Mangifera indica L.) in North Western Ethiopia (Pawe)

Mango (Mangifera indica L.) is considered as one of the most popular fruits among millions of people in the tropical area and increasingly in the developed countries. Anthracnose, caused by the fungus Colletotrichum gloeosporioides, is the most important pre- and post-harvest disease of mango. The objective of this research was to evaluate the prevalence of different promising antagonistic Trichoderma and Bacillus spp. on phyloplane of mango in Ethiopia and to evaluate their antagonistic potential against the pathogen. A total of 19 mango fields were surveyed and anthracnose affected all fields. Culture studies on potato dextrose agar for evaluation of antibiosis activity of Trichoderma spp. and Bacillus spp. revealed that they have inhibitory and lytic effect on C. gloeosporioides, which is an indication of their potential biocontrol agent for management of mango anthracnose as an alternative to chemical control. Significant differences (p?<?0.05) were observed among Bacillus isolates in causing lysis of pathogen mycelium, when inoculated on actively growing colony of C. gloeosporioides. Maximum reduction in growth rate of pathogen was observed with Bacillus spp. (B50), which restricted the growth to 2.7?mm compared to 8.3?mm in the control with 67.5% efficacies. There were similar effects (p?<?0.05) among Trichoderma spp. in formation of inhibition zones and lysis by varying degrees up to 59.7% efficacies in reducing linear growth of the pathogen in dual culture.     

不同油茶无性系炭疽病抗性及主要生理指标分析

为选育对炭疽病高抗的油茶(Camellia oleifera)良种,以5个闽西当地的油茶无性系为材料,采用病情指数法进行调查,评价其炭疽病抗性,并测定各无性系叶片的过氧化物酶(POD)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)活性及可溶性蛋白含量等指标,分析油茶炭疽病抗性与其主要生理指标的相关性。结果表明,参试的5个油茶无性系中,高抗无性系1个(新罗2号)、中抗无性系3个(河田2号、红山1号、漳平2号)、低感无性系1个(武平2号);不同无性系之间的POD、SOD、CAT活性及可溶性蛋白含量差异均达极显著水平(P<0.01)。相关性分析显示,POD活性、SOD活性、可溶性蛋白含量与油茶炭疽病的感病指数成负相关,CAT活性与感病指数的相关性未达显著水平。综上所述,不同油茶无性系对炭疽病的抗性各不相同,且其主要生理指标与抗性有一定的相关性,其中新罗2号无性系对炭疽病抗性强,主要生理指标也相对较高。该结果为油茶抗炭疽病良种选育及抗病机理研究提供依据。     

New report of Colletotrichum gloeosporioides causing anthracnose of Pisonia alba in India

Anthracnose was observed on Pisonia alba plants as irregular, black, necrotic spots that often coalesce to form large necrotic area on leaves. A fungus, consistentlyisolated from symptomatic leaves was identified as C. gloeosporioides on the basis of morphological and cultural characteristics. The fungus produced white mycelia, which became dark grey with later formation of numerous salmon pink coloured spore masses. The conidia were hyaline, unicellular, aseptate and oval to cylindrical with rounded ends and were 10–20 μm long and 3–5 μm wide. Pathogenicity tests conducted on healthy detached leaves of Pisonia plants showed typical anthracnose symptoms afterfour to seven days. This is the first report of anthracnose of Pisonia alba.     

The distinctive population structure of Colletotrichum species associated with olive anthracnose in the Algarve region of Portugal reflects a host–pathogen diversity hot spot

Anthracnose ( Colletotrichum spp.) is an important disease of olive fruits. Diversity and biogeographic relationships of the olive anthracnose pathogens in the Algarve (Portugal) were investigated, along with host association patterns and disease levels during 2004–2007, to test the hypothesis that this region is a host–pathogen diversity hot spot. Diverse Colletotrichum acutatum and Colletotrichum gloeosporioides populations were identified based on rRNA-internal transcribed spacer and partial β-tubulin 2 gene sequences of 95 isolates. Spatial and temporal variations in the occurrence of the eight genetic entities of the pathogens were linked to olive biogeography. Disease occurrence patterns suggest that C. acutatum populations are more stable pathogens, while C. gloeosporioides populations appear to be more influenced by favourable conditions. Three unique C. acutatum populations were identified, but none of the eight populations were dominant, with the most frequent type representing only 27%. Thus, the population structure of olive anthracnose pathogens in the Algarve is distinct from other parts of Portugal and other world locations, where only one or two genetic entities are dominant. This pattern and level of genetic diversity in a restricted area, where oleaster (wild olive tree), ancient landraces and modern cultivars of olive occur in close proximity, suggests the Algarve as a centre of diversity of the anthracnose pathogens and corroborates recent work suggesting western Mediterranean as an important centre of olive diversity and domestication.     

Integrated control of Colletotrichum gloeosporioides on mango fruit in Taiwan by the combination of Bacillus subtilis and fruit bagging

Anthracnose disease caused by Colletotrichum gloeosporioides in Jingkwang mango grown in Taiwan was significantly reduced by the integration of fruit bagging with either B. subtilis strain LB5 or fungicides. The combined treatments were most effective in reducing early infection during the 2004 season, leading to 56.4 and 58.3% reduction, respectively, while in 2003 reduction accounted for 51 and 52.3%, respectively. Post-harvest application of B. subtilis strain LB5 cell suspensions on fruits already treated by bagging, bagging+LB5 and baggingfungicides in the field reduced anthracnose incidence significantly at all tested concentrations. These results indicate that biocontrol efficacy of B. subtilis LB5 may be due to the prevention of early fruit infection, thereby reducing significantly anthracnose incidence in ripening fruits to much lower levels than those obtained by using a conventional single post-harvest treatment.     

Role of Antifungal Gallotannins,Resorcinols and Chitinases in the Constitutive Defence of Immature Mango (Mangifera indica L.) against Colletotrichum gloeosporioides

Conidia of Colletotrichum gloeosporioides germinate and form infection hyphae on inoculated, immature mango but remain quiescent until fruit ripening. Antifungal resorcinols have previously been implicated for quiescence of C. gloesoporioides and Alternaria alternata on mango. This study revealed the presence of a mixture of several gallotannins with glycosidic linkages, including 1,2,3,4,6‐penta‐O‐galloyl‐β‐D‐glucopyranose, with significant antifungal activity in the unripe mango fruit peel. Gallotannin antifungal activity was greater in a cultivar resistant (295.8 mm² inhibition) to anthracnose than in a susceptible (148.4 mm² inhibition) cultivar. In both, the activity decreased with ripening but the decrease was 10% less in the resistant cultivar. Three recorcinols, 5‐pentadecylresorcinol, 5‐(12‐cis‐heptadecenyl)resorcinol, AR 21 and another resorcinol derivative were present in the unripe fruit peel and all declined during ripening, more significantly the 5‐(12‐cis‐heptadecenyl)resorcinol and AR 21. Mango latex, when drained out, separates into an oily and aqueous phase. The aqueous phase showed significant chitinase activity and the ability to digest conidia of C. gloeosporioides. The oily phase has previously been reported to contain resorcinols. Draining fruits of latex soon after harvest resulted in greater incidence and severity of anthracnose at ripe stage. Chitinase activity was less in the peel of fruits from which latex was drained. The evidence suggests that the resistance of unripe mango to C. gloeosporioides is because of an elaborate constitutive defence system comprising antifungal resorcinols, gallotannins and chitinases.     

中国柱花草炭疽病原菌遗传多态性的RAPD分析

在对中国柱花草炭疽病进行广泛调查和病原采样收集的基础上,利用RAPD分子标记技术对43个代表性菌株进行了基因组DNA分析,并与276份国外菌株进行了综合聚类分析。 结果表明所用8个引物的扩增片段位于0.3～2.8kb之间, 菌株间呈现显著的DNA多态性。以柱花草起源中心——南美的柱花草炭疽菌分类为基础,中国柱花草炭疽菌可划分成3大类型即Ⅱ、Ⅲ、Ⅵ类。中国菌株与来自柱花草起源中心——南美的菌株相比之下,其生物多样性和遗传变异性则相对简单。就中国菌株而言海南菌株与广西、广东菌株相比多样性较丰富, 中国柱花草胶孢炭疽菌正在出现种内遗传分化。 从聚类结果看,通常来自于同一个地理区域或同一个寄主基因型的菌株聚成一类, 即同一RAPD聚类组内的菌株通常来自于同一寄主基因型或同一地理区域。说明来自不同寄主基因型或物种的炭疽菌在遗传基因上具有专化性,而地理上隔离的国家或地区的柱花草炭疽病原菌各自具有相对独立的进化途径。     

Effect of Cuticular Wax Layers of Green and Red Pepper Fruits on Infection by Colletotrichum gloeosporioides

Colletotrichum gloeosporioides isolate KG13 caused necrotic, sunken anthracnose symptoms on unwounded, wax-removed, and wounded green pepper fruits and on wounded red fruits 7 days after inoculation. Hypersensitive reactions with small brownish discolorations, on some occasions, were found on unwounded red fruits. The isolate produced whitish symptoms with brown margins, but not the typical anthracnose on red fruits wax-removed by chloroform treatment. Generally, wax-removed red fruits, but not green ones, produced larger lesions and more conidia than untreated controls. Wounded pepper fruits had larger lesions than those with other treatments. More germinated conidia, appressoria, and infection hyphae were found on wax-removed fruits than on controls; however, differences between green and red fruits were not found. Cuticular wax layers of fruits were dissolved partially by chloroform and the outer epidermal cells were disrupted slightly. Anthracnose development was negatively related with fruit developmental stage. Well-developed fruits had more cuticular wax than less developed fruits. These results suggest that the cuticular wax layers of pepper fruits may play a significant role in fruit infection by C. gloeosporioides isolate KG13, and mainly determine the incompatibility of red fruits to the isolate. Biochemical differences may also play a role.