Clemson University, Coastal Research and Education Center, Charleston, SC 29414.
Plant Dis. 2018 Jul;102(7):1365-1375. doi: 10.1094/PDIS-12-17-1953-RE. Epub 2018 May 7.
At least 24 species of cucurbits from 13 genera are known to be susceptible to gummy stem blight, caused by three species of Stagonosporopsis. Cankers that are formed on crowns and stems play an important role in the disease cycle and the survival of the pathogen. Fourteen cucurbit species of unknown susceptibility representing 12 genera, four taxonomic tribes, and four geographic origins were inoculated with Stagonosporopsis citrulli in Charleston, SC, in spring 2015, spring 2016, and fall 2016 to evaluate their level of susceptibility to gummy stem blight and the ability of the pathogen to reproduce on crown cankers. An additional species, Cucumis melo, was included as a reference due to its known high susceptibility. Data sets of area under the disease progress curve (AUDPC) for foliar severity and crown cankers, final percentage of diseased leaf area, final percentage of plants with cankers, final percentage of plants with fruiting bodies, and rates of increase in canker incidence were analyzed to evaluate susceptibility. Results were similar for datasets of AUDPC and final ratings but there were more differences for AUDPC. In all experiments, Apodanthera sagittifolia, Ecballium elaterium, and Kedrostis leloja were at least as susceptible to foliar blight as the reference C. melo. K. leloja was as susceptible to crown cankers as C. melo in all experiments and A. sagittifolia and E. elaterium were among the species most susceptible to crown cankers in two experiments. Coccinia grandis was highly resistant to gummy stem blight and had a few cankers only in fall 2016. Sicana odorifera and Zehneria pallidinervia also consistently grouped with the most resistant species. Incidence of crown cankers on Cucumis melo and K. leloja increased at the fastest rate of all species in all experiments and had, along with E. elaterium, the highest incidence of crowns with fruiting bodies. In general, the most susceptible species also were most suitable for reproduction of the pathogen and had the fastest disease progression. The tribes Benincaseae and Cucurbiteae had consistently lower levels of foliar blight than Bryonieae and Coniandreae. The tribe Benincaseae had a consistently lower AUDPC for canker incidence than Bryonieae and Coniandreae. The species originating from Europe (E. elaterium) was consistently most susceptible to both symptoms, while African species grouped with the least susceptible species in all experiments. To the best of our knowledge, this is the first report of susceptibility to gummy stem blight of 14 species and the first report of susceptibility of the cucurbit tribes Coniandreae and Gomphogyneae. This expands the host range of Stagonosporopsis citrulli to 37 species representing 21 genera and seven tribes in the family Cucurbitaceae. This study demonstrates the importance of crown cankers as reproductive sites for S. citrulli.
至少有 24 种葫芦科植物的 13 属被认为易患由三种尾孢菌引起的细菌性疫病。冠部和茎部形成的溃疡在疾病循环和病原体存活中起着重要作用。2015 年春季、2016 年春季和 2016 年秋季，在南卡罗来纳州查尔斯顿用尾孢菌接种了 14 种未知敏感性的葫芦科植物，代表 12 个属、4 个分类部落和 4 个地理起源，以评估它们对细菌性疫病的敏感性和病原体在冠部溃疡上繁殖的能力。由于其已知的高敏感性，添加了一个物种，甜瓜。对叶片严重程度和冠部溃疡的疾病进展曲线下面积 (AUDPC)、最终叶片面积发病率、最终患病植物比例、最终带菌植物比例和溃疡发病率的增加率进行了分析，以评估其敏感性。AUDPC 和最终评分的数据集结果相似，但 AUDPC 的差异更大。在所有实验中，箭叶橙、瓜尔豆和非洲核果木的叶片枯萎病的敏感性至少与对照甜瓜一样高。在所有实验中，K. leloja 对冠部溃疡的敏感性与甜瓜一样，在两个实验中，箭叶橙和瓜尔豆是最易患冠部溃疡的物种之一。苦瓜对细菌性疫病高度抗性，仅在 2016 年秋季有少数溃疡。蛇瓜和长梗山柑也一直与最抗的物种归为一类。在所有实验中，甜瓜和 K. leloja 上的溃疡发病率以最快的速度增加，并且与瓜尔豆一起，具有最高的带菌体发病率。一般来说，最敏感的物种也最适合病原体的繁殖，并且疾病进展最快。Benincaseae 和 Cucurbiteae 族的叶片枯萎病发病率始终低于 Bryonieae 和 Coniandreae 族。Benincaseae 族的溃疡发病率 AUDPC 始终低于 Bryonieae 和 Coniandreae 族。起源于欧洲的物种（瓜尔豆）对这两种症状都始终最为敏感，而非洲物种在所有实验中都与最不敏感的物种归为一类。据我们所知，这是对 14 种细菌性疫病敏感性的首次报道，也是对 Coniandreae 和 Gomphogyneae 葫芦科的首次报道。这将尾孢菌的宿主范围扩大到 37 种，代表葫芦科的 21 个属和 7 个部落。本研究表明，冠部溃疡是尾孢菌的重要繁殖场所。
