O'Neal E S, Davis D D
Department of Plant Pathology and Environmental Microbiology, The Pennsylvania State University, University Park 16802.
Plant Dis. 2015 Aug;99(8):1070-1077. doi: 10.1094/PDIS-07-14-0722-RE. Epub 2015 Jun 17.
Verticillium nonalfalfae, causal agent of Verticillium wilt, is being considered as a biocontrol for the highly invasive Ailanthus altissima in Pennsylvania. This soilborne fungus is extremely virulent on Ailanthus and rapidly transmitted from diseased to healthy trees within Ailanthus stands. The rapid transmission of the fungus could be facilitated by root grafts, but neither root graft formation in Ailanthus nor Verticillium transmission by root grafts in trees has been reported. Here, V. nonalfalfae transmission between diseased and healthy Ailanthus trees via intraspecific root grafts and clonal growth is evaluated. Using air-spade excavation, dye translocation, and root graft inoculations, functional root grafts were detected between Ailanthus trees and transmission of V. nonalfalfae across root grafts demonstrated. Inoculation of one Ailanthus parent stem resulted in 187 root sprouts showing Verticillium wilt symptoms 12 months after inoculation. This study revealed that clonal growth and root grafts, normally advantageous growth habits, leave Ailanthus stands vulnerable to widespread V. nonalfalfae infection. This study also broadens the understanding of the Ailanthus-Verticillium pathosystem, growth strategies of invasive Ailanthus, and epidemiology of Verticillium wilt within trees.
黄萎病菌（Verticillium nonalfalfae）是黄萎病的致病因子，正被考虑用于宾夕法尼亚州对极具侵入性的臭椿（Ailanthus altissima）进行生物防治。这种土壤传播的真菌对臭椿具有极强的毒性，且能在臭椿林内从患病树木迅速传播至健康树木。真菌的快速传播可能借助根嫁接得以促进，但此前尚未有关于臭椿根嫁接形成以及根嫁接在树木间传播黄萎病菌的报道。在此，对患病和健康臭椿树之间通过种内根嫁接和克隆生长进行黄萎病菌传播的情况进行了评估。通过空气挖掘、染料转运和根嫁接接种，检测到臭椿树之间存在功能性根嫁接，并证实了黄萎病菌可通过根嫁接进行传播。对接种一棵臭椿亲本茎干后，12个月内有187个根蘖出现黄萎病症状。这项研究表明，克隆生长和根嫁接这两种通常具有优势的生长习性，会使臭椿林易受黄萎病菌广泛感染。该研究还拓宽了对臭椿 - 黄萎病菌病理系统、入侵性臭椿的生长策略以及树木内黄萎病流行病学的认识。
