Abstract
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.
Highlights
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 [1]
Four endophytic fungi (CEF-818, CEF-714, CEF-642, and CEF-193) used in previous experimental were isolated from cotton roots, and were identified as Penicillium simplicissimum, Leptosphaeria sp, Talaromyces flavus and Acremonium sp via morphology and ITS phylogenetic analysis [23]
There are some reports on P. simplicissimum and Leptosphaeria sp. as bioagents
Summary
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 [1]. This disease has progressively increased in many regions and has become a serious obstacle to cotton production in China [2]. Use of biological control agents to control Verticillium wilt on cotton is a promising eco-friendly strategy [6]. 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 [9,10,11]
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