State Key Laboratory of Tree Genetics and Breeding (SKLTGB), Chinese Academy of Forestry (CAF), Haidian District 100091, Beijing, China.
Nanjing Forestry University (NJFU), Nanjing 210037, JiangSu Province, China.
Plant Dis. 2020 Feb;104(2):493-509. doi: 10.1094/PDIS-05-19-1009-RE. Epub 2019 Nov 30.
(Myrtaceae, Myrtales) trees are widely cultivated for commercial purposes worldwide. Calonectria leaf blight is one of the most prominent diseases associated with trees grown in plantations in Asia and South America. Recently, symptoms of leaf blight, shoot blight, tree death, and seedling rot caused by species have been observed in commercial plantations and nurseries in Leizhou Peninsula, which is one of the most densely -planted areas in southern China. Disease samples were collected from 10 species and a number of , , and hybrid genotypes that were planted on plantations at 13 sites and one experimental nursery. A total of 773 isolates of were obtained from 683 plantation trees and nursery seedlings. Fifty-five representative isolates from all the surveyed sites and species/genotypes were selected for molecular identification. These 55 isolates were identified by DNA sequence analyses based on the calmodulin (), histone H3 (), translation elongation factor 1-alpha (), and β-tubulin () gene regions, as well as a combination of morphological characteristics. The results indicated that these 55 isolates present one single species, . Determined by sequences of , , , and gene regions, only two genotypes were identified among the 55 representative isolates; 54 of these isolates share the same genotype, suggesting that the genetic diversity of collected during this study was relatively low. A growth study indicated that is a high-temperature species. The mating test results suggested that is heterothallic or lacks the ability to recombine to produce fertile progeny. Inoculation results showed that causes leaf blight and stem rot, resulting in tree death of the two widely planted genotypes in southern China, and that the two genotypes differ significantly in their susceptibility to infection by . A selection program to develop planting stocks with high levels of resistance to Calonectria leaf blight in China during the long-term should be urgently initiated.[Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
桃金娘科（Myrtaceae）、桃金娘目（Myrtales）的树木在世界范围内广泛种植，用于商业目的。节菱孢叶枯病是与亚洲和南美洲种植园中种植的树木相关的最突出的疾病之一。最近，在中国南方种植最密集的地区之一的雷州半岛的商业种植园和苗圃中，观察到了由节菱孢属（Calonectria）引起的叶枯病、梢枯病、树木死亡和幼苗腐烂的症状。从 10 个种和一些榕属（Ficus）、蒲桃属（Syzygium）和杂交基因型的商业种植园中采集了病样，这些基因型种植在 13 个地点和一个实验苗圃中。从 683 株种植园中树木和苗圃幼苗中总共获得了 773 株节菱孢菌（Calonectria）分离株。从所有调查地点和种/基因型中选择了 55 个代表分离株进行分子鉴定。这些 55 个分离株通过基于钙调蛋白（calmodulin）（）、组蛋白 H3（histone H3）（）、翻译延伸因子 1-α（translation elongation factor 1-alpha）（）和β-微管蛋白（β-tubulin）（）基因区域的 DNA 序列分析，以及形态特征的组合来鉴定。结果表明，这些 55 个分离株呈现出一个单一的种，即节菱孢榕专化型（Calonectria ficus-nectria）。通过 calmodulin（）、histone H3（）、translation elongation factor 1-alpha（）和 β-tubulin（）基因区域的序列确定，在 55 个代表分离株中仅鉴定出两种基因型；其中 54 个分离株具有相同的基因型，表明在本研究中收集的节菱孢菌的遗传多样性相对较低。生长研究表明，节菱孢榕专化型是一种高温物种。交配试验结果表明，节菱孢榕专化型是异宗配合的，或者缺乏重组产生可育后代的能力。接种结果表明，节菱孢榕专化型引起叶枯病和茎腐病，导致中国南方两种广泛种植的榕属基因型树木死亡，并且这两种基因型对感染节菱孢榕专化型的敏感性有显著差异。在中国，应该紧急启动一个长期的项目，选择具有高水平抗节菱孢叶枯病的桃金娘科种植材料。
