Effect of postharvest salicylic acid treatment on fungal decay and some postharvest quality factors of kiwi fruit

The effect of salicylic acid (SA) treatment at different concentrations on fungal decay and some quality factors of kiwi fruit (Actinidia deliciosa var. Hayward) in postharvest conditions were studied. Results experiment showed that SA at all applied concentrations inhibited grey mould growth. The SA application significantly decreased weight loss percentage and increased life storage fruits. Also, SA positively affected on postharvest quality factors including total soluble solids (TSS), titratable acidity (TA), antioxidant, ascorbic acid and pH value. It was observed that treated fruits with SA at concentration 5?mM had the highest TSS, TA, ascorbic acid and antioxidant content and it had the lowest decay and acidity. Thus, these results showed that SA has strong impact on postharvest decay and fruit quality of kiwi fruit.     

番茄灰霉病内生拮抗细菌的分离筛选初报

采用常规法对番茄植株进行内生细菌的分离 ,结果表明 ,不同品种不同生长时期 ,内生细菌的数量有所不同 ;同一品种不同生长时期不同部位 ,内生细菌的数量也存在变化。在所分离的 96个菌株中 ,有 7个菌株对番茄灰霉病有拮抗性 ,其中菌株x 9和x 1 5的拮抗效果较为明显 ,对番茄灰霉病防病效果达到 40 %和2 5 %。此 7个菌株对番茄植株无致病性 ,且对番茄苗无明显促生长作用。     

不同寄主来源的灰葡萄孢对番茄的致病力分化研究

从安徽合肥、蚌埠、长丰、和县等市、县的番茄、辣椒、草莓、葡萄等发病寄主上分离鉴定获得18个灰葡萄孢Botrytis cinerea菌株,采用菌丝块创伤接种法,分别测定了上述不同寄主来源的灰葡萄孢菌对番茄果实和叶片的致病力.结果表明,所有供试菌株接种番茄果实后均引起发病,但不同菌株所致病斑的平均直径有显著差异,显示灰葡萄孢菌株间对番茄果实的致病力存在明显分化.按照在番茄果实上所致病斑的平均直径大小可将供试菌株致病力划分为较强、中等和较弱3种类型.总体来说,来自番茄的菌株对番茄果实的致病力较强,来自草莓、葡萄和辣椒的菌株对番茄果实的致病力较弱,但来自相同寄主的菌株间致病力也存在差异,菌株致病力差异与菌株地域来源无明显相关.供试灰葡萄孢菌株接种番茄叶片后,除CF1外,均可引起番茄叶片发病,但不同菌株所致番茄叶片病斑的平均直径也有显著差异;供试菌株对番茄叶片的致病力差异与菌株的寄主和地域来源无显著相关.     

不同寄主来源的灰葡萄孢对番茄的致病力分化研究

Eighteen isolates of Botrytis cinerea were obtained from the diseased plant tissue collected in Hefei, Bengbu, Changfeng and Hexian in Anhui province, by means of tissue isolating method. The pathogenicity of the isolates of B. cinerea from different hosts to the fruits and leaves of tomato were investigated by applying wound inoculation with mycelial blocks. The results showed that all of the tested isolates caused grey mould on tomato fruits, but there was significant difference in the average diameters of the lesions caused by different isolates, suggesting that there was significant differentiation in pathogenicity of B. cinerea strains to tomato fruits among isolates. According to the average diameters of the lesions on tomato fruits, the pathogenicity of the all isolates was classified into three categories: strong, intermediate and weak. In general, the isolates from tomato were more strongly pathogenic to tomato fruits than the isolates from strawberry, grape and capsicum. However, there was difference in pathogenicity among the different isolates from the same host, and the pathogenicity difference was not obviously related to the localities of isolates. After inoculating of tomato leaves, all of the tested isolates except CF3 caused grey mould on tomato leaves, but there was significant difference in the average diameters of the lesions caused by different isolates; and the difference in pathogenicity to tomato leaves was not obviously related to the host and locality of isolates.     

Freezing and freeze-drying of the bacterium Rahnella aquatilis BNM 0523: study of protecting agents, rehydration media and freezing temperatures

Aims: The aim of the present study was to evaluate and compare freezing and freeze‐drying treatments for conserving Rahnella aquatilis (BNM 0523) with the goal to achieve an adequate commercial formulation of this biocontrol agent. Methods and Results: The effect of several protective agents, rehydration media and freezing temperatures on the viability and functional activity of the R. aquatilis was investigated. The storage stability at 3 months and 4 years was determined by checking the viability of the cells and their biocontrol capability against Botrytis cinerea by measuring the percentage of reduction of disease severity on apple. The best results were obtained by the freeze‐drying of the cells using a mixture of skimmed nonfat milk 10%, yeast extract 0·5% and glucose 1% as the protecting and rehydrating medium, and a quickly freezing (?70°C) before the freeze‐drying. In this case, the viability of the cells after 4 years was 98%, and their antagonistic ability showed a little decrease with respect fresh cells. Conclusions: The studies showed that R. aquatilis was resistant to freezing and freeze‐drying when it was used a mixture of cryoprotectants and that it was possible to obtain inoculums with high viability and good effectiveness for reduction of decay caused by B. cinerea. Significance and Impact of the study: This study is probably the first report about the resistance of R. aquatilis to freezing and freeze‐drying treatments and shows that these operations could be useful for obtaining a commercial formulation of this biocontrol agent.     

Control of postharvest decay on cherry tomatoes by marine yeast Rhodosporidium paludigenum and calcium chloride

Aims: In this study, the potential of calcium chloride (CaCl₂) application to improve the efficacy of the marine antagonist Rhodosporidium paludigenum in controlling postharvest diseases of cherry tomatoes was assessed. Methods and Results: CaCl₂ alone was found not to have any direct influence on the population growth of R. paludigenum in NYDB cultures or in cherry tomato wounds. However, the combined treatments with 1 × 10⁸ cells ml^?1R. paludigenum and CaCl₂ at the concentration from 0·5 to 2% showed high activities to reduce black rot caused by Alternaria alternata in cherry tomato wounds, significantly higher than those of R. paludigenum or CaCl₂ alone. Meanwhile, 0·5% CaCl₂ in combination with 1 × 10⁸ cells ml^?1R. paludigenum greatly inhibited the natural decay of cherry tomatoes in 21 days’ storage at 25°C. Conclusions: The combination of R. paludigenum and CaCl₂ enhances the inhibition of black rot and natural decay of postharvest cherry tomatoes. The results from this study provide a new way to improve the efficiency of R. paludigenum in maintaining the quality of postharvest fruits and vegetables. Significance and Impact of the Study: The marine yeast R. paludigenum combined with CaCl₂ has greatly potential use as an alternative to chemical fungicides in inhibiting postharvest decay on cherry tomatoes.     

Biological control of grey mould in strawberry fruits by halophilic bacteria

Aims:  Grey mould caused by Botrytis cinerea is an economically important disease of strawberries in Tunisia and worldwide. The aim of this study was to select effective halophilic bacteria from hypersaline ecosystems and evaluate the abilities of antifungal bacteria to secrete extracellular hydrolytic enzymes, anti- Botrytis metabolites and volatiles.
Methods and Results:  Grey mould was reduced in strawberry fruits treated with halophilic antagonists and artificially inoculated with B. cinerea . Thirty strains (20·2%) were active against the pathogen and reduced the percentage of fruits infected after 3 days of storage at 20°C, from 50% to 91·66%. The antagonists were characterized by phenotypic tests and 16S rDNA sequencing. They were identified as belonging to one of the species: Virgibacillus marismortui , B. subtilis , B. pumilus , B. licheniformis , Terribacillus halophilus , Halomonas elongata , Planococcus rifietoensis , Staphylococcus equorum and Staphylococcus sp. The effective isolates were tested for antifungal secondary metabolites.
Conclusions:  Moderately halophilic bacteria may be useful in biological control against this pathogen during postharvest storage of strawberries.
Significance and Impact of the study:  The use of such bacteria may constitute an important alternative to synthetic fungicides. These moderate halophiles can be exploited in commercial production and application of the effective strains under storage and greenhouse conditions.