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Evaluation of foliar fungus?mediated interactions with below and aboveground enemies of the invasive plant Ageratina adenophora

ABSTRACT: Abstract Plant–fungal associations are frequently key drivers of plant invasion success. Foliar fungi can benefit their invasive hosts by enhancing growth promotion, disease resistance and environmental stress tolerance. However, the roles of foliar fungi may vary when a given invasive plant faces different stresses. In this study, we designed three independent experiments to evaluate the effects of a foliar fungus, Colletotrichum sp., on the growth performance of the invasive plant Ageratina adenophora under different soil conditions, as well as the responses of A. adenophora to the foliar fungal pathogen Diaporthe helianthi and to herbivory. We found that the soil type was the most influential factor for the growth of A. adenophora. The role of the foliar fungus Colletotrichum sp. varied in the different soil types but generally adversely affected leaf development in A. adenophora. Colletotrichum sp. may be a weak latent foliar pathogen that can enhance the pathogenicity of D. helianthi on leaves of A. adenophora and marginally reduce signs of herbivory by natural insects in the wild on A. adenophora seedlings. In general, the benefits of the foliar fungus Colletotrichum to the fitness of A. adenophora are not significant in the context of this experimental design. However, our data highlight the need to consider both aboveground and belowground biota in different soil habitats when evaluating the effects of foliar fungi. Soil type played the most important role in the growth of A. adenophora, and the role of the foliar fungus Colletotrichum sp. varied according to different habitats but in general adversely affected the growth of A. adenophora. The Colletotrichum sp. might be a weak latent pathogen and enhanced the pathogenicity of Diaporthe helianthi on leaves of A. adenophora. Colletotrichum sp. marginally reduced the feeding frequency of seedlings by natural enemies in the wild.

SUBMITTER: Fang K

PROVIDER: S-EPMC7790651 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature

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Project description:Ageratina adenophora originating from central America has flooded forests, pastures, and farmland in more than 40 tropical and subtropical countries, causing huge ecological disasters and economic losses. In this paper, we intended to use a complex inoculum composed of Pseudomonas putita and Clostridium thermocellum to in-situ compost A. adenophora debris and then to compare the phytotoxicity of extracts from uncomposted and composted A. adenophora (UCA and CA respectively) to barley seed germination and young seedling growth. A field experiment was finally conducted to reveal the effects of UCA and CA on barley nutrients uptake, yield, grain quality, soil enzyme activities, microbial biomass and biodiversity. In-situ composting sharply decreased 4,7-dimethyl-1-(propan-2-ylidene)-1,4,4a,8a-tetrahydronaphthalene- 2,6(1H,7H)-dione(DTD) and 6-hydroxy-5-isopropyl-3,8-dimethyl-4a,5,6,7,8,8a-hexahydronaphthal en-2(1 H)-one(HHO) from 2096.3 and 743.7 mg kg-1 in uncomposted A. adenophora to 194.4 and 68.19 mg kg-1 in composted A. adenophora. UCAE showed negative influences on seed germination performances (except lower rates on germination percentage). The mechanism may be the inhibition of bio-macromolecules hydrolysis (including proteins, starch, and phytin) in endosperms and their hydrolysates for forming new plants. CAE promoted seed germination and seedling growth, increased chlorophyll levels in leaves, and stimulated dehydrogenase and nitrate reductase activities in plants, while UCAE got opposite performance. Compared with chemical fertilizers, application of CA in combination with chemical fertilizers significantly improved plant nutrient uptake (nitrogen, phosphorus, and potassium), yield, grain quality, quantity of 16S rDNA sequences, richness and diversity of bacterial communities in contrast to UCA which behaved otherwise. Taken together, the use of the microbial agent to in-situ compost A. adenophora may be an effective approach for agricultural use of A. adenophora debris as a plant-friendly organic fertilizer, being undoubtedly worth advocating.

Project description:Plant-growth promoting rhizobacteria (PGPR) play a vital role in soil fertility and crop production. The rhizosphere of many crop plants has been well documented by screening PGPR for their plant-growth promoting (PGP) mechanisms. However, the rhizosphere of grass species that may act as potential habitats for novel PGPR remains relatively unexplored. Ageratina adenophora is a noxious weed that has invaded more than 40 tropical and subtropical countries in Asia, Oceania, Africa, and Europe. Its presence has led to changes in plant species composition, reducing their biodiversity and destroying ecosystem function. In this study, we screened 1,200 bacterial strains isolated from the rhizosphere soil of A. adenophora in three floristic regions in Yunnan Province, China. Samples were screened for their in vitro ability for N-fixation, production of the plant growth regulator indole-3-acetic acid (IAA), and the synthesis of 1-amino-cyclopropane-1-carboxylate (ACC) deaminase, which controls the levels of ethylene in developing plant roots. We found that 144 strains showed at least one of these PGP attributes. 16S rRNA gene sequencing showed that most (62.5%) of the samples were bacteria closely related to members of the genera Pseudomonas (27 strains), Providencia (20 strains), Chryseobacterium (14 strains), Ensifer (12 strains), Enterobacter (nine strains), and Hafnia (eight strains). Their abundance and biodiversity in the soil of individual floristic regions correlate positively with the invasion history of A. adenophora. From these PGP bacterial strains, KM_A34 (Pantoea agglomerans), KM_C04 (Enterobacter asburiae), and KM_A57 (Pseudomonas putida), which had the greatest in vitro ability of N-fixation, and IAA and ACC deaminase production, respectively, were selected. The strains were evaluated for their effect on the seed germination and growth of soybean, faba bean, pea, wheat, and Chinese cabbage other than A. adenophora. Chamber experiments showed these strains significantly (P < 0.05) increased (14.2-43.4% over the controls) germination rates of the soybean, faba bean, pea, and/or Chinese cabbage seeds. They also reduced relative seed germination times (20.8-48.8% over the controls) of soy bean, faba bean and/or wheat seeds. Greenhouse pot experiments showed that they significantly (P < 0.05) promoted the aboveground and belowground height of plant foliage (12.1-23.1% and 11.5-31.4% over the controls, respectively) and/or the dry weights (16.1-33.5% and 10.6-23.4% over the controls, respectively) of the soy bean, faba bean, pea, wheat and/or Chinese cabbage. These data indicate that the rhizosphere microbiota of A. adenophora contain a PGPR pool that may be used as bioinoculants to improve the growth and productivity of these crops.

Project description:Root endophytic nitrogen-fixing bacteria (reNFB) have been proposed as important contributors to the invasiveness of exotic legumes; however, the reNFB of invasive nonlegumes has received less attention. In particular, the growth-promoting effect of reNFB on invasive plants remains unknown. In this study, 131 strains of potential nitrogen-fixing bacteria were isolated and purified from the roots of the invasive plant, Ageratina adenophora, in Southwest China. Phylogenetically, these reNFB were categorized into three phyla at 97% sequence identity that included Proteobacteria (92.4%), Actinobacteria (4.6%), and Firmicutes (3.1%). The dominant isolates ranked by number were Pseudomonas (80 isolates, 61.1%), Rhizobium (12 isolates, 9.2%), and Duganella (11 isolates, 8.4%). The community composition and diversity of A. adenophora reNFB were markedly different across study regions. The capacity of these reNFB to accumulate indolyl-3-acetic acid (IAA), solubilize phosphate, and produce siderophores was determined. All 131 isolates of reNFB accumulated IAA, 67 isolates solubilized phosphate, and 108 isolates produced siderophores. Among the three dominant genera of reNFB, Pseudomonas had the highest phosphorus solubilization and siderophore production, while the accumulation of IAA in the genus Duganella was the lowest. Interestingly, the calculated reNFB Shannon diversity index of each A. adenophora individual was negatively correlated with the capacity of reNFB to produce growth-promoting products. Six randomly selected isolates from three dominant genera were further used to conduct inoculation experiments, and all isolates showed significant positive growth-promoting effects on A. adenophora seedlings. The contribution of reNFB to the root biomass was higher than that to the shoot biomass. Our results suggest that reNFB, similar to soil or nodular nitrogen-fixing bacteria, can potentially promote plant growth and may play an important role in the invasion of nonleguminous plants. More detailed studies on the correlation between reNFB and invasive plants are necessary.

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Evaluation of foliar fungus?mediated interactions with below and aboveground enemies of the invasive plant Ageratina adenophora

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