EFFECT OF PLANT EXTRACTS AND GROWTH SUBSTRATES ON CONTROLLING DAMPING-OFF IN PINUS TECUNUMANII SEEDLINGS

ABSTRACT Damping-off is considered one of the most limiting phytosanitary problems in conifer seedling production because it may cause massive damage or total plant death in short time periods. This pathology is caused by a complex of microorganisms, the most common of which are Fusarium spp. and Rhizoctonia spp. This study evaluated the effect of growth substrates and plant extracts at different concentrations on germination and incidence of disease in Pinus tecunumanii plants. The plants were inoculated with the damping-off pathogen Fusarium oxysporum and treatments were applied in a completely randomized design with a factorial arrangement of 4x2x3. This corresponded to four substrates (pine bark, rice hull, coconut husk and sandy soil (4:1)); two plant extracts (Matricaria chamomilla and Datura stramonium), and three concentrations of each extract (Control concentration: 0%, Concentration 1: 50 % and Concentration 2: Undiluted). Each treatment had three repetitions, with 25 plants per repetition. The growth substrates affected germination; the most effective of these were sandy soil (4:1) and pine bark, with 90% and 92% germination at day 20, respectively. No significant difference was observed between the germination obtained with these substrates and that obtained with coconut husk after day 19. Meanwhile, all of the extracts had a significant effect on controlling the disease when they were combined with the substrates, with the exception of coconut husk. With this last substrate the incidence of disease was lower than 4% without the application of plant extracts; this indicates that coconut husk discourages the development of the disease on its own.

摘要 猝倒病（Damping-off）被认为是针叶树苗木育苗中最具限制性的植物检疫性病害之一，因其可在短时间内造成大规模危害乃至植株完全死亡。该病害由复合病原微生物群落引发，其中最常见的致病菌为镰孢菌属（Fusarium spp.）与丝核菌属（Rhizoctonia spp.）。本研究评估了不同浓度栽培基质与植物提取物对特库马南洋松（Pinus tecunumanii）幼苗萌发率及病害发病率的影响。试验以猝倒病病原菌尖孢镰孢菌（Fusarium oxysporum）接种供试幼苗，采用完全随机析因设计，设置4×2×3的因子组合：4种栽培基质（松树皮、稻壳、椰壳及体积比4:1的沙壤土）、2种植物提取物（洋甘菊（Matricaria chamomilla）与曼陀罗（Datura stramonium）），以及每种提取物的3个浓度梯度（对照组：0%、浓度1组：50%稀释液、浓度2组：未稀释原液）。每组处理设置3次重复，每次重复包含25株幼苗。

试验结果表明，栽培基质对幼苗萌发率存在显著影响：其中表现最优的为体积比4:1的沙壤土与松树皮，在第20天的萌发率分别达90%与92%；在第19天后，该两种基质的萌发率与椰壳基质的萌发率无统计学显著差异。与此同时，除椰壳基质外，其余所有基质搭配植物提取物后，均对病害防控展现出显著效果。仅使用椰壳基质而不施加植物提取物时，病害发病率低于4%，这表明椰壳基质本身即可抑制病害的发生与发展。