Use of nitrate non‐utilizing (nit) mutants to determine phenological stages at which Botrytis cinerea infects wine grapes causing botrytis bunch rot

Botrytis bunch rot (BBR), caused by Botrytis cinerea, degrades wine grapes during ripening, even though infection can occur as early as flowering. Effective BBR management requires knowledge of whether some stages of fruit development are more important than others in relation to infection and BBR severity at harvest. Bunches of Vitis vinifera ‘Sauvignon blanc’ and/or ‘Pinot noir’ were inoculated in two vineyard trials and one glasshouse trial with nitrate non‐utilizing (nit) mutant strains at three phenological stages: early flowering, pre‐bunch closure (PBC) and veraison. Isolates recovered from symptomless berries at veraison and from bunches with symptoms at harvest were screened to measure the incidence of the nit strains used in the inoculations. It was found that latent infections, which resulted in BBR at harvest, could become established at all three phenological stages and no single stage was associated with greater latent incidence or harvest severity than any other stage. It was concluded that a proportion of BBR at harvest resulted from the expression of latent infections that had accumulated throughout the season. However, the time between infection and BBR symptom expression in near‐ripe grape berries was sufficiently short for polycyclic secondary infection to also contribute to epidemic development.     

青贮饲料中霉菌毒素的产生及对反刍动物健康的影响

青贮饲料营养丰富,适口性好,易消化且能够长期保存,是反刍动物日粮中最重要的组成部分之一。青贮饲料在收获、发酵以及取用过程中都有可能受到霉菌毒素的污染,其中主要包括黄曲霉毒素B1、玉米赤霉烯酮、脱氧雪腐镰刀菌烯醇、赭曲霉毒素A、伏马菌素以及其他真菌次级代谢产物。反刍动物摄取发霉青贮饲料,会对其生产性能及健康产生严重影响。加强青贮饲料收获前、青贮过程及饲喂期的管理,对于减少反刍动物饲料中的霉菌毒素污染至关重要。此外,某些霉菌抑制剂或微生物接种剂也可降低毒素的污染水平。本文主要就青贮饲料生产过程中出现的各种霉菌、霉菌毒素以及其对反刍动物健康的影响进行了综述,旨在为控制青贮饲料制作和饲喂过程中霉菌毒素的污染,降低经济损失提供参考。     

香葱灰霉病病原鉴定及其生物学特性研究

为明确香葱灰霉病病原及其生物学特性,采用单孢分离法分离香葱灰霉病病原菌,依据病原菌形态特征及r DNA-ITS序列分析结果,鉴定香葱灰霉病病原为灰葡萄孢菌(Botrytis cinerea Pers.),同时对其生物学特性进行研究。结果表明:病原菌在供试的10种培养基上均能生长,最适宜培养基为PDA培养基;供试的9种碳源和11种氮源中,最利于病原菌菌丝生长的碳源为可溶性淀粉,氮源为酵母粉;在pH值为4.0~12.0条件下,病原菌都能生长,最适pH值为5.0~6.0;病原菌在4~30℃均能生长,适合病原菌菌丝生长的温度为15~25℃,25℃时病原菌菌丝不仅生长快且非常浓密,温度高于30℃菌丝停止生长;菌丝致死温度是52℃(10 min)。     

Molecular,morphological and pathogenic diversity of Sclerotinia sclerotiorum isolates from common bean (Phaseolus vulgaris) fields in Argentina

White mould, caused by Sclerotinia sclerotiorum, is one of the most threatening fungal diseases occurring across major bean production regions worldwide. In Argentina, under favourable weather conditions, up to 100% seed yield losses occur on susceptible common bean cultivars. The aim of this study was to characterize the diversity of S. sclerotiorum isolates from six dry bean fields in the main production area of Argentina by means of molecular, morphological (mycelium colour, number and pattern of sclerotia distribution) and pathogenic approaches. Among 116 isolates analysed, high genotypic and morphological variability was observed. A total of 52 mycelial compatibility groups (MCGs) and 59 URPs (universal rice primers) molecular haplotypes were found. All the MCGs were location specific, while only 12% of the URP haplotypes were shared among locations. The molecular analysis of variance revealed a significant differentiation among populations, with higher genetic variability within the populations analysed than among them. The aggressiveness of the isolates towards bean seedlings was assessed in the greenhouse. Most of the isolates were highly aggressive, while no variation among locations was observed. The information generated in the present study provides, for the first time, information on the variability of S. sclerotiorum associated with white mould in the main common bean production area in Argentina. In addition, the findings suggest the occurrence of both clonal and sexual reproduction in the populations analysed. This work contributes to the development of sustainable management strategies in bean production aimed to minimize yield losses due to white mould.     

番茄灰霉病在果实上的侵染部位及防治新技术

 通过发病规律及人工接种研究,明确了番茄灰霉病菌Botrytis cinerea初侵染番茄果实的主要部位为残留的花瓣处及柱头处,随后扩展到果蒂部、脐部,最后蔓延到果实的其它部位。据此,在国内外首次提出了一种防治番茄果实灰霉病的新方法,在番茄用2,4-D蘸花后7~15 d(幼果直径10~20 mm)摘除残留的花瓣及柱头,防效达80%以上,对番茄单果重无影响。     

贵州柑橘主栽种对炭疽病和煤污病的抗性鉴定

为了解贵州柑橘7个主栽种(椪柑、朱橘、沙田柚、温州蜜橘、南丰蜜桔、纽贺尔脐橙和默科特桔橙)对柑橘炭疽病和煤污病的抗病性,采用室内离体鉴定和田间调查的方法,对柑橘主栽种的炭疽病和煤污病的抗性进行了鉴定.结果表明,默科特桔橙对炭疽病和煤污病的抗性最强,而朱橘最易感这2种病.     

Hierarchical models for white mould in snap bean

Limitations on the acceptable proportion (incidence) of pods with white mould may lead to the rejection of entire fields of processing snap bean. The low tolerances (no more than 2% to 6% of pods with white mould) are difficult to estimate with sufficient precision in the field when time is limited. These constraints motivated this study of white mould across three spatial hierarchical levels: pods, plants and quadrats consisting of two adjacent plants within rows. Hierarchical relationships are required when designing formal rules for estimating the incidence of pods with white mould from units higher in the spatial hierarchy. Disease assessments were made on all pods from 38 within‐row transects of 40 plants each of the snap bean cultivar Hystyle. Using probability‐based principles, equations were derived and fitted to data on the incidence of white mould on pods (i_pod), plants (i_pad) and quadrats (i_q(2)), which led to a function directly linking i_pod to i_q(2). The variance of i_pod increased with i_q(2), but that may be of little consequence at the lower values of i_q(2) likely to be associated with i_pod values at processor‐set tolerances. For example, at i_q(2) = 0.1 there was a 92% probability that i_pod was less than 0.02. Assessing i_q(2) may be more efficient than directly estimating i_pod because i_q(2) was about an order of magnitude higher than i_pod. Results suggest it may be feasible to design sampling plans for estimating the proportion of pods with white mould from an assessment of the proportion of diseased quadrats.     

Microencapsulation of clove essential oil improves its antifungal activity against Penicillium digitatum in vitro and green mould on Navel oranges

?Relatively high levels of clove essential oil (CEO) necessary for in vivo inhibition of postharvest pathogens imply that its antifungal activity should be reinforced. Hence, this study aimed to determine whether microencapsulation technology enhances the antifungal activity of CEO against Penicillium digitatum, the causal agent of citrus green mould, in vitro and on Navel oranges. Microencapsulation of CEO resulted in a respective reduction of minimum inhibitory concentration and minimum fungicidal concentration from 500 μg/ml to 125 μg/ml and 250 μg/ml, indicating the enhancement of fungistatic and fungicidal activity with respect to that of the pure oil. CEO microcapsules had the best control of lesion diameter and decay development (0.79 mm, 8.64%) in Navel oranges after 5 days’ storage at 25°C, followed by pure oil treatment (4.2 mm, 55.56%). In the vapour phase, CEO microcapsules also exhibited the highest ability to control green mould of Navel oranges. Furthermore, CEO microcapsules showed stronger suppressive activity of spore germination and germ tube elongation of P. digitatum than pure oil. These results indicate that the antifungal activity of CEO was considerably enhanced when it was converted into a microcapsule.     

霉菌完整结构观察标本的研制

对最佳霉菌完整结构观察标本制作方法进行了研究。实验表明：最好的方法是载片培养法，最合适的培养基是土豆汁培养基，土豆培养基凝固剂的用量以1．5％为佳，最好的封片剂为加拿大树脂。