U.S. Vegetable Laboratory, USDA, ARS, Charleston, SC 29414.
ORISE participant at U.S. Vegetable Laboratory, USDA, ARS, Charleston, SC 29414.
Plant Dis. 2018 Jul;102(7):1290-1298. doi: 10.1094/PDIS-09-17-1384-RE. Epub 2018 Apr 26.
Powdery mildew (PM) is a major foliar disease causing serious economic losses of cucurbit crops grown in the United States. The pathogen Podosphaera xanthii, which causes PM, is known to infect seedlings, stems, foliage, petioles, and fruit of cucurbit crops. In recent years, grafting watermelon on resistant rootstocks for managing soilborne diseases has been gaining popularity in the U.S.A. However, grafting for managing foliar diseases has not yet received adequate attention. Three greenhouse experiments were conducted during the summer months of 2012, 2013, and 2014 to determine if PM-resistant rootstocks could impart resistance to a susceptible watermelon scion. Susceptible watermelon scion 'Mickey Lee' seedlings were grafted onto 25 watermelon (Citrullus lanatus, C. amarus, C. mucosospermus) and four bottle gourd (Lagenaria siceraria) rootstocks. Grafted plants were inoculated with a 2 × 10 conidia ml suspension of P. xanthii conidia and disease severity was rated 14 days after inoculation. Mickey Lee grafted on six PM-resistant watermelon rootstocks had significantly (P ≤ 0.05) lower PM severity on cotyledons, 2nd true leaf, and upper leaves (rating for 3rd to 7th or 8th true leaf) compared with Mickey Lee grafted on susceptible watermelon USVL677-PMS or bottle gourd USVL848-PMS rootstocks. However, some of the resistant watermelon rootstocks did not impart significant resistance to the scion. The resistant bottle gourd rootstocks USVL482-PMR and USVL351-PMR provided significantly greater levels of resistance, compared with many of the resistant watermelon rootstocks. Grafting watermelon on resistant rootstocks may help mitigate the effects of PM on susceptible scion seedlings.
白粉病（PM）是一种主要的叶部病害，会给美国种植的葫芦科作物造成严重的经济损失。引起 PM 的病原菌 Podosphaera xanthii 已知会感染葫芦科作物的幼苗、茎、叶片、叶柄和果实。近年来，在美国，嫁接抗病砧木来防治土传病害的方法越来越受欢迎。然而，嫁接防治叶部病害还没有得到足够的重视。2012 年、2013 年和 2014 年的夏季，进行了 3 个温室试验，以确定 PM 抗性砧木是否可以赋予感病西瓜接穗抗性。将感病西瓜接穗‘Mickey Lee’幼苗嫁接到 25 个西瓜（Citrullus lanatus、C. amarus、C. mucosospermus）和 4 个葫芦（Lagenaria siceraria）砧木上。嫁接植株用 2×10 个分生孢子 ml P. xanthii 分生孢子悬浮液接种，接种后 14 天评估病情严重程度。与嫁接在易感西瓜 USVL677-PMS 或葫芦 USVL848-PMS 砧木上的接穗相比，嫁接在 6 个 PM 抗性西瓜砧木上的 Mickey Lee 幼苗的子叶、第 2 真叶和上部叶片（第 3 至第 7 或第 8 真叶的评级）上的 PM 严重程度显著（P ≤ 0.05）降低。然而，一些抗性西瓜砧木并没有赋予接穗显著的抗性。与许多抗性西瓜砧木相比，抗性葫芦砧木 USVL482-PMR 和 USVL351-PMR 提供了更高水平的抗性。嫁接抗病砧木可能有助于减轻 PM 对感病接穗幼苗的影响。
