Plant Biology Division, The Samuel Roberts Noble Foundation Inc., 2510 Sam Noble Parkway, Ardmore, OK 73401, USA.
Mol Plant Pathol. 2010 May;11(3):325-34. doi: 10.1111/j.1364-3703.2010.00616.x.
Phymatotrichum (cotton or Texas) root rot is caused by the soil-borne fungus Phymatotrichopsis omnivora (Duggar) Hennebert. The broad host range of the fungus includes numerous crop plants, such as alfalfa and cotton. Together with an overview of existing knowledge, this review is aimed at discussing the recent molecular and genomic approaches that have been undertaken to better understand the disease development at the molecular level with the ultimate goal of developing resistant germplasm.
Phymatotrichopsis omnivora (Duggar) Hennebert [synonym Phymatotrichum omnivorum (Shear) Duggar] is an asexual fungus with no known sexual stage. Mitosporic botryoblastospores occasionally form on epigeous spore mats in nature, but perform no known function and do not contribute to the disease cycle. The fungus has been affiliated erroneously with the polypore basidiomycete Sistotrema brinkmannii (Bres.) J. Erikss. Recent phylogenetic studies have placed this fungus in the ascomycete order Pezizales. HOST RANGE AND DISEASE SYMPTOMS: The fungus infects most dicotyledonous field crops, causing significant losses to cotton, alfalfa, grape, fruit and nut trees and ornamental shrubs in the south-western USA, northern Mexico and possibly parts of central Asia. However, this fungus does not cause disease in monocotyledonous plants. Symptoms include an expanding tissue collapse (rot) of infected taproots. In above-ground tissues, the root rot results in vascular discoloration of the stem and rapid wilting of the leaves without abscission, and eventually the death of the plant. Characteristic mycelial strands of the pathogen are typically present on the root's surface, aiding diagnosis.
Confocal imaging of P. omnivora interactions with Medicago truncatula roots revealed that infecting hyphae do not form any specialized structures for penetration and mainly colonize cortical cells and eventually form a mycelial mantle covering the root's surfaces. Cell wall-degrading enzymes have been implicated in penetration and symptom development. Global gene expression profiling of infected M. truncatula revealed roles for jasmonic acid, ethylene and the flavonoid pathway during disease development. Phymatotrichopsis omnivora apparently evades induced host defences and may suppress the host's phytochemical defences at later stages of infection to favour pathogenesis.
No consistently effective control measures are known. The long-lived sclerotia and facultative saprotrophism of P. omnivora make crop rotation ineffective. Chemical fumigation methods are not cost-effective for most crops. Interestingly, no genetic resistance has been reported in any of the susceptible crop species.
棉花或得克萨斯州）根腐病是由土壤传播的真菌 Phymatotrichopsis omnivora（Duggar）Hennebert 引起的。该真菌的宿主范围广泛，包括许多作物，如苜蓿和棉花。本文综述了现有的知识，旨在讨论最近在分子和基因组方面所做的研究，这些研究旨在从分子水平上更好地了解疾病的发展，最终目标是开发抗性种质资源。
Phymatotrichopsis omnivora（Duggar）Hennebert[同义词 Phymatotrichum omnivorum（Shear）Duggar]是一种无性真菌，没有已知的有性阶段。Mitosporic botryoblastospores 偶尔在自然界的地上孢子垫上形成，但不具有已知的功能，也不会对疾病循环做出贡献。该真菌曾被错误地归为多孔菌担子菌 Sistotrema brinkmannii（Bres.）J. Erikss。最近的系统发育研究将该真菌置于子囊菌目 Pezizales 中。
该真菌感染大多数双子叶大田作物，在美国西南部、墨西哥北部和可能的中亚部分地区，造成棉花、苜蓿、葡萄、水果和坚果树以及观赏灌木的严重损失。然而，该真菌不会引起单子叶植物的疾病。症状包括受感染主根的组织（腐烂）扩张性崩溃。在地上组织中，根腐病导致茎的维管束变色和叶片迅速萎蔫而不脱落，最终植物死亡。病原体的特征菌丝体通常存在于根的表面，有助于诊断。
对 Phymatotrichopsis omnivora 与 Medicago truncatula 根相互作用的共焦成像显示，感染的菌丝不会形成任何专门的穿透结构，主要定植于皮层细胞，最终形成覆盖根部表面的菌丝套。细胞壁降解酶与穿透和症状发展有关。受感染 M. truncatula 的全基因表达谱显示，茉莉酸、乙烯和类黄酮途径在疾病发展过程中发挥作用。Phymatotrichopsis omnivora 显然逃避了诱导的宿主防御，并且可能在感染后期抑制宿主的植物化学防御，以有利于发病。
目前还没有一致有效的控制措施。P. omnivora 的长寿性菌核和兼性腐生使轮作无效。化学熏蒸方法对大多数作物来说都不具有成本效益。有趣的是，在任何易感作物中都没有报道过遗传抗性。
