Alternative Control of Alternaria Brown Spot in Tangerine

Alternaria brown spot is considered the main disease of tangerines in the State of Paraiba. The objective of work was to evaluate vegetal tinctures from bitter melon (Momordica charantia) and guava (Psidium guajava) leaves, as an alternative control for Alternaria brown spot in tangerine. The effects of vegetal tinctures were tested in leaves and fruits (detached) of tangerine “Dancy” inoculated with tangerine pathotype of Alternaria alternata. The effect of tinctures on mycelium growth and spore germination of the pathogen was tested. Tinctures at 20% concentration promoted reduction of disease severity. A reduction of 80% in the diameter of leaf lesions was observed for bitter melon tinctures and 75.3% for guava tinctures. In fruits, the reduction was 48.4% (bitter melon tinctures) and 43.3% (guava tinctures). Guava tinctures, starting at a concentration of 5%, inhibited 100% of mycelium growth of tangerine pathotype of A. alternata, while the use of bitter melon tinctures inhibited 100% of mycelium growth starting at a concentration of 10%. The greater sensitivity to tinctures observed when these were added to the culture medium when compared to inoculation in leaves and fruits may be explained due to the higher exposition of the pathogen to the active principle when the vegetal tinctures were added to the culture medium, than when tinctures were sprayed over the vegetal surface in fruits and leaves. The number of germinated spores decreases 76.7% and 82% when using tinctures from guava and bitter melon (20%). Tinctures from bitter melon and guava are potential tools for alternative management of the Alternaria brown spot in tangerine “Dancy”.

苹果早期落叶病广谱拮抗菌株的筛选、鉴定与抑制作用研究

采用平板对峙法、平皿叶片法,从苹果树根际土壤样品中分离筛选得到7株苹果早期落叶病广谱拮抗菌株,其中菌株BS24对苹果早期落叶病主要病害斑点落叶病和褐斑病的病原菌拮抗效果最佳,抑菌带宽度分别为9.5mm、9.2mm。综合菌株形态特征、生理生化特征及16S rDNA序列分析,将其鉴定为枯草芽孢杆菌(Bacillus subtilis)。试验表明菌株BS24无细胞培养滤液可显著抑制苹果早期落叶病主要病原菌的菌丝生长和孢子萌发。菌株抑菌谱较广,对苹果其他几种病害如灰斑病、圆斑病、轮斑病、腐烂病、轮纹病、炭疽病等的病原菌均有明显拮抗效果。菌株BS24具有良好的苹果早期落叶病生防应用的潜力。

苹果感染斑点落叶病菌后几种酶活性的变化

研究了苹果品种秦冠(高抗)和富士(高感)接种斑点落叶病菌(A lternaria a lternata f.sp.m a li)后叶片内5种酶活性的变化。结果表明,苹果接种斑点落叶病菌后超氧化物岐化酶(SOD)、过氧化氢酶(CAT)和多酚氧化酶(PPO)变化趋势相似,都是先升高后降低;苯丙氨酸解氨酶(PAL)、过氧化物酶(POD)活性变化差别较大,秦冠的POD活性峰值是富士的182%,PAL活性峰值是富士的478%,均达到极显著差异。初步认为PAL和POD在抗斑点落叶病中有很大的作用。

云南苹果新品种抗斑点落叶病鉴定与评价

苹果斑点落叶病是引起苹果树早期落叶的主要病害,也是目前在我国苹果产区普遍发生、危害最严重的病害之一,推广和使用抗病品种是控制该病害的有效措施和方法。本研究系统调查了分布在云南的7个苹果品种红富士、新嘎啦、皇家嘎啦、斯维塔、短枝富士、金世纪和玉华富士的田间自然发病率和病情指数,同时进行室内人工接种鉴定。结合两种方法,对7种苹果新品种对斑点落叶病的抗性进行了评价。田间调查结果显示,其余6个品种的抗性均高于现在的主栽品种红富士,适合于在云南推广。室内抗性鉴定结果显示,红富士品种对斑点落叶病的抗性程度是7,其他苹果品种均为5,抗性表现型红富士品种为S(感病),其余品种均为MR(中抗)。本研究为苹果品种的推广使用提供了依据。

苹果内生细菌动态分布及其对斑点落叶病的拮抗作用

采用常规分离法对不同生长季节苹果树的不同部位进行了内生细菌分离.结果表明,内生细菌的分离几率和数量不同.通过平板对峙培养和发酵液抑菌活性测定,在所分离的118个菌株中,筛选出7株对苹果斑点落叶病菌(Alternaria alternata f. sp. Mali)具有较强拮抗作用的菌株,其中菌株B86和B91的发酵滤液在活体上对苹果斑点落叶病的防治效果显著,分别为73.72%和75.32%.两菌株培养滤液对病菌分生孢子萌发具有抑制作用,并造成芽管畸形膨大,呈泡囊状,泡囊消解破裂;两菌株产生的抑菌物质具有热稳定性.表明B86和B91菌株具有一定的生防潜力.

苹果斑点落叶病菌对戊唑醇敏感基线建立及抗性突变体适合度

本研究测定了苹果斑点落叶病菌对戊唑醇的敏感性,并建立了敏感基线;在此基础上,室内筛选获得了9株抗戊唑醇突变体,对其适合度进行了测定,为指导戊唑醇防治苹果斑点落叶病提供理论依据。在山西省5个地市未使用过戊唑醇及同类药剂的果园中采集分离得到64株苹果斑点落叶病菌,敏感性测定结果表明,其EC50值在0.768 7~2.673 8μg·mL^(-1)之间,平均值为1.622 4±0.558 2μg·mL^(-1),呈连续性单峰曲线,可作为苹果斑点落叶病菌对戊唑醇的相对敏感基线。通过紫外线(UV)诱导获得低抗突变体6株,药剂驯化获得中抗突变体3株。2株中抗突变体抗药性可稳定遗传;低抗突变体在无药剂胁迫时,药剂敏感性上升。抗性突变体适合度测定结果显示,突变体菌丝生长速率、产孢量、孢子萌发率及分生孢子竞争力均低于敏感菌株。突变体在无药情况下致病力比敏感菌株弱。