Coastal Research and Education Center, Clemson University, Charleston, SC 29414-5329.
Plant Dis. 2017 Nov;101(11):1895-1902. doi: 10.1094/PDIS-03-17-0451-RE. Epub 2017 Aug 30.
Gummy stem blight can develop in greenhouses on cucurbit seedlings grown as scions and rootstocks for grafting. When diseased seedlings are cut during grafting, Stagonosporopsis spp., the fungal pathogens causing gummy stem blight, may be transferred to healthy seedlings. The objective of this study was to evaluate efficacy of disinfectant treatments to prevent or reduce transmission during cutting and grafting. A blade contaminated with mycelium and spores from a culture of S. citrulli transferred the pathogen to 72%, 73%, and 55% of the second, third, and fourth seedlings, respectively, cut in sequence when 100% of the first seedlings cut were infected. Kleengro (didecyl dimethyl ammonium chloride), Physan 20 (dimethyl benzyl ammonium chloride), and Virkon S (potassium peroxymonosulfate) were ineffective when sprayed onto watermelon seedlings before or after cutting hypocotyls with a contaminated blade. Dipping a contaminated blade in 0.3% sodium hypochlorite, 0.4% Physan 20, or 70% or 95% ethanol before cutting watermelon hypocotyls significantly (P = 0.01) reduced incidence of gummy stem blight compared with water but did not prevent transmission. Soaking a contaminated blade for 3 s in 95% ethanol, 30 s in 0.8% sodium hypochlorite, or flaming the blade after dipping in 95% ethanol, prevented transmission. In a grafting experiment, both the watermelon scion and the interspecific hybrid squash rootstock were cut with contaminated or contaminated and treated blades before grafting. Sterilizing a contaminated blade by flaming significantly (P = 0.01) reduced incidence of gummy stem when compared with a 1-s dip in ethanol, a 1-s dip in Physan 20, or water. Disease incidences in these treatments were 11%, 45%, 100%, and 100%, respectively. Using heat, ethanol, or sodium hypochlorite to disinfest cutting tools may reduce transmission of S. citrulli during cucurbit grafting.
苦瓜蔓枯病可在温室中发生，主要侵害作为接穗和砧木的葫芦科幼苗。在嫁接过程中，如果接穗和砧木的幼苗受到感染，那么在切割时，导致苦瓜蔓枯病的病原菌 Stagonosporopsis spp. 可能会转移到健康的幼苗上。本研究的目的是评估消毒剂处理的效果，以防止或减少切割和嫁接过程中的传播。当用受 S. citrulli 培养物的菌丝体和孢子污染的刀片连续切割第二、第三和第四株幼苗时，分别有 72%、73%和 55%的幼苗被感染，而第一株幼苗的 100%都被感染。在切割西瓜幼苗的下胚轴之前或之后，用 Kleengro（双十二烷基二甲基氯化铵）、Physan 20（二甲基苄基氯化铵）和 Virkon S（过氧单硫酸钾）喷雾处理不能有效预防或减少蔓枯病的发生。在切割西瓜下胚轴之前，用 0.3%次氯酸钠、0.4% Physan 20 或 70%或 95%乙醇浸泡受污染的刀片，可以显著降低（P = 0.01）蔓枯病的发病率，但不能防止传播。将受污染的刀片浸泡在 95%乙醇中 3 秒，在 0.8%次氯酸钠中浸泡 30 秒，或在浸泡在 95%乙醇后燃烧刀片，可防止传播。在嫁接实验中，用受污染或受污染和经处理的刀片切割西瓜接穗和种间杂交南瓜砧木，然后进行嫁接。用火焰灼烧受污染的刀片消毒，与乙醇浸泡 1 秒、Physan 20 浸泡 1 秒或水浸泡相比，显著降低了苦瓜蔓枯病的发病率（P = 0.01）。这些处理的发病率分别为 11%、45%、100%和 100%。使用热、乙醇或次氯酸钠来消毒切割工具可能会减少苦瓜嫁接过程中 S. citrulli 的传播。
