Ahimera N, Driever G F, Michailides T J
University of California-Davis, Kearney Agricultural Center, Parlier 93648.
Plant Dis. 2003 Jul;87(7):846-853. doi: 10.1094/PDIS.2003.87.7.846.
Experiments were conducted between 1999 and 2001 to monitor the presence of propagules of Botryosphaeria dothidea and frequencies of latent infections on pistachio leaves and fruit clusters and to determine their relationships to panicle and shoot blight severity in commercial orchards. Numbers of B. dothidea propagules recovered from washing leaves and fruit clusters varied among the growing seasons and sampling dates. Lower numbers of B. dothidea propagules were obtained in 1999 and 2001 than in 2000. For the orchard in Glenn County, up to 75 propagules per leaf and 21 propagules per fruit cluster were recorded in 1999, compared with 365 and 248 propagules per leaf and fruit cluster, respectively, in 2000. Although more propagules were detected per leaf, the infection levels were higher on fruit clusters, suggesting that pistachio fruit is more susceptible to B. dothidea infection than leaves. Latent infections were detected as soon as leaves or fruit clusters started to expand and more infections were obtained in 2000 than 1999 or 2001. Significant (P < 0.05) relationships between propagules on leaves or frequency of infections on leaves (independent variables) and propagules on fruit clusters or frequency of infected fruit clusters (dependent variables) with r values ≥ 0.50 provide support for the role of latent infection in panicle and shoot blight later in the season. Propagules on leaves and fruit clusters were not significantly correlated to disease severity, but frequencies of latent infection on leaves and fruit clusters were positively correlated (P ≥ 0.05) with leaf and fruit disease severity under field conditions with r ranging between 0.25 and 0.42. Quantitative relationships between latent infections and disease severity may be incorporated in a prediction model for disease development or be used to develop a risk assessment method to guide growers in their effort to control panicle and shoot blight of pistachio.
1999年至2001年间开展了多项实验，以监测葡萄座腔菌的繁殖体在开心果叶片和果穗上的存在情况及潜伏感染频率，并确定它们与商业果园中穗枯病和枝枯病严重程度的关系。从冲洗叶片和果穗中回收的葡萄座腔菌繁殖体数量在不同生长季节和采样日期有所不同。1999年和2001年获得的葡萄座腔菌繁殖体数量低于2000年。对于格伦县的果园，1999年每片叶子记录到多达75个繁殖体，每个果穗记录到21个繁殖体，而2000年每片叶子和每个果穗分别记录到365个和248个繁殖体。尽管每片叶子检测到的繁殖体更多，但果穗上的感染水平更高，这表明开心果果实比叶片更容易受到葡萄座腔菌的感染。一旦叶片或果穗开始展开就检测到潜伏感染，2000年获得的感染比1999年或2001年更多。叶片上的繁殖体或叶片感染频率（自变量）与果穗上的繁殖体或感染果穗频率（因变量）之间存在显著（P < 0.05）关系，r值≥ 0.50，这为潜伏感染在季节后期穗枯病和枝枯病中的作用提供了支持。叶片和果穗上的繁殖体与病害严重程度没有显著相关性，但在田间条件下，叶片和果穗上的潜伏感染频率与叶片和果实病害严重程度呈正相关（P ≥ 0.05），r值在0.25至0.42之间。潜伏感染与病害严重程度之间的定量关系可纳入病害发展预测模型，或用于开发风险评估方法，以指导种植者努力控制开心果穗枯病和枝枯病。
