Reaction of squash and butternut squash genotypes to Phytophthora capsici

ABSTRACT Phytophthora capsici causes significant losses in squash (Cucurbita moschata) and butternut squash (Cucurbita maxima), including root and crown rot, leaf blight and fruit rot, which can result in up to 100% loss in production. The objective of this study was to evaluate the reaction of squash and butternut squash genotypes to P. capsici. Initially an experiment was conducted to evaluate the aggressiveness of isolates of P. capsici from different regions. Later two experiments were carried out in a greenhouse with 16 genotypes of C. moschata and seven of C. maxima in different years, using the most aggressive isolates, PCA 40 and PCA 43 identified as the most aggressive in a preliminary test. As control we used the hybrid cultivar Jabras and the pepper cultivar Cascadura Ikeda (susceptibility patterns to the pathogen). The genotypes were sown in pots of four liters containing autoclaved soil. Fourteen days later, plants were inoculated by depositing 3.0 mL of the suspension of 2.0x104 zoospores/mL in the soil, near to plant stem. The disease incidence was evaluated 8 days after inoculation. The experiments were conducted in a randomized block design with five replicates of four plants. The genotypes showed different levels of disease resistance, TX 10350, PHYT-043, CNPH-3001-1 and MAM-2523-1 stood out because they showed greater degree of resistance to P. capsici in both trials. However, none of the genotypes showed complete resistance. The results indicate the promising use of these genotypes to obtain resistant lines, aiming to obtain hybrid cultivars resistant to Phytophthora root rot.

摘要 辣椒疫霉（Phytophthora capsici）可对中国南瓜（Cucurbita moschata）与胡桃南瓜（Cucurbita maxima）造成显著经济损失，引发根冠腐病、叶枯病及果腐病，可造成高达100%的产量损失。本研究旨在评估两类南瓜基因型对辣椒疫霉的抗病反应。首先开展试验以评估不同地区辣椒疫霉菌株的致病力。随后于不同年份在温室中开展两项试验，共纳入16份中国南瓜基因型与7份胡桃南瓜基因型，并采用初步试验中筛选出的致病力最强的菌株PCA 40与PCA 43。本试验以杂交品种Jabras以及对该病原菌具典型感病性的辣椒品种Cascadura Ikeda作为对照。供试基因型播种于装有高压灭菌土壤的4升盆钵中。接种14天后，于植株茎基附近土壤中施加3.0 mL浓度为2.0×10⁴个/mL的游动孢子悬浮液进行接种。接种8天后调查病害发病率。试验采用随机区组设计，每处理设置5次重复，每次重复包含4株植株。结果显示，不同基因型的抗病水平存在显著差异，其中TX 10350、PHYT-043、CNPH-3001-1及MAM-2523-1在两项试验中均表现出对辣椒疫霉的较高抗性。但所有供试基因型均未表现出完全抗病性。本研究结果表明，上述优异基因型可用于培育抗病株系，以期获得抗辣椒疫霉根腐病的杂交品种。