Date Published: January 20, 2017
Publisher: Public Library of Science
Author(s): Yuan Yuan, Hongjie Feng, Lingfei Wang, Zhifang Li, Yongqiang Shi, LiHong Zhao, Zili Feng, Heqin Zhu, Vijai Gupta.
Verticillium wilt is a soil-borne disease, and severely limits the development of cotton production. To investigate the role of endophytic fungi on Verticillium wilt, CEF-818 (Penicillium simplicissimum), CEF-714 (Leptosphaeria sp.), CEF-642 (Talaromyces flavus.) and CEF-193 (Acremonium sp.) isolated from cotton roots were used to assess their effects against cotton wilt disease caused by a defoliating V. dahliae strain Vd080. In the greenhouse, all treatments significantly reduced disease incidence and disease index, with the control efficacy ranging from 26% (CEF-642) to 67% (CEF-818) at 25 days (d) after inoculation. In the disease nursery, compared to controls (with disease incidence of 33.8% and disease index of 31), CEF-818, CEF-193, CEF-714 and CEF-642 provided a protection effect of 69.5%, 69.2%, 54.6% and 45.7%, respectively. Especially, CEF-818 and CEF-714 still provided well protection against Verticillium wilt with 46.9% and 56.6% or 14.3% and 33.7% at the first peak of the disease in heavily infected field, respectively (in early July). These results indicated that these endophytes not only delayed but also reduced wilt symptoms on cotton. In the harvest, the available cotton bolls of plant treated with CEF-818 and CEF-714 increased to 13.1, and 12.2, respectively. And the seed cotton yield significantly increased after seed bacterization with CEF-818 (3442.04 kg/ha) compared to untreated control (3207.51 kg/ha) by 7.3%. Furtherly, CEF-818 and CET-714 treatment increased transcript levels for PAL, PPO, POD, which leads to the increase of cotton defense reactions. Our results indicate that seed treatment of cotton plants with CEF-818 and CET-714 can help in the biocontrol of V. dahliae and improve seed cotton yield in cotton fields. This study provided a better understanding of cotton-endophyte interactions which will aid in developing effective biocontrol agents for Verticillium wilt of cotton in futhre.
Verticillium wilt, caused by a soil-inhabiting fungus V. dahliae Kleb., is the most overwhelming or distressing disease of cotton, which can cause severe yield and quality losses . Moreover, this disease has progressively increased in many regions and has become a serious obstacle to cotton production in China . However, lack of upland cotton germplasm immune or highly resistant to the defoliating pathotype, only little progress has been made towards introduction of disease-resistant breeding [3–4]. In addition, there are no effective fungicides currently available for controlling the disease . Use of biological control agents to control Verticillium wilt on cotton is a promising eco-friendly strategy . Over the last two decades, rhizosphere bacteria, such as Pseudomonas spp. and Serratia plymutica, have been shown to be effective antagonists of Verticillium wilt [7–8]. Recent studies have indicated that endophytes colonize the internal tissues of plants and can improve plant growth and plant health [9–11].
In a previous study, 642 endophytic fungi were obtained from 12 Verticillium-wilt-resistant cotton varieties, which were divided into 27 genera based on morphology and ITS (internal transcribed spacer region) phylogenetic analysis. Thirty-nine isolates exhibited potential fungi stasis against the pathogen at varying degrees. Among them, CEF-818, CEF-714, CEF-642 and CEF-193 were and identified as Penicillium simplicissimum, Leptosphaeria sp., Talaromyces flavus. and Acremonium sp. respectively. . T. flavus was reported as an antagonist for control of Verticillium wilt in cotton, eggplant, potato and tomato [29–32]. Isolates in Acremonium spp. have been used as biocontrol fungi in management of root knot nematode disease [33–38]. There are some reports on P. simplicissimum and Leptosphaeria sp. as bioagents. For example, Arabidopsis thaliana grown in soil amended with barley grain inocula of P. simplicissimum GP17-2 or receiving root treatment with its culture filtrate exhibited clear resistance to Pseudomonas syringae pv . In this study, we further explored their potential for biological control against cotton Verticillium wilt disease.