Multiple Species of Asteraceae Plants are Susceptible to Root Infection by the Necrotrophic Fungal Pathogen Sclerotinia sclerotiorum

The necrotrophic fungal pathogen Sclerotinia sclerotiorum can cause disease on numerous plant species, including many important crops. Most S. sclerotiorum-incited diseases of crop plants are initiated by airborne ascospores produced when fungal sclerotia germinate to form spore-bearing apothecia. However, basal stalk rot of sunflower occurs when S. sclerotiorum sclerotia germinate to form mycelia within the soil which subsequently invade sunflower roots. To determine if other plant species in the Asteraceae family are susceptible to root infection by S. sclerotiorum, cultivated sunflower (Helianthus annuus L.) and seven other Asteraceae species were evaluated for S. sclerotiorum root infection by inoculation with either sclerotia or mycelial inoculum. Additionally, root susceptibility of sunflower was compared to that of dry edible bean and canola, two plant species susceptible to S. sclerotiorum but not known to display root-initiated infections. Results indicated that multiple Asteraceae family plants are susceptible to S. sclerotiorum root infection after inoculation with either sclerotia or mycelium. These observations expand the range of plant hosts susceptible to S. sclerotiorum root infection, elucidate differences in root inoculation methodology, and emphasize the importance of soil-borne infection to Asteraceae crop and weed species.

Abundance of Associated Arbuscular Mycorrhizal Fungi with Pioneer Plants in Affected Area by Mount Merapi Eruption

Arbuscular mycorrhizal fungi (AMF) with mutualism symbiosis with plants are associated with the Fabaceae family's pioneer plants. This study aims to determine the percentage of AMF in the roots and the AMF spore's abundance in the rhizosphere of pioneer plants Calopogonium mucunoides Desv. and Vigna Unguiculata (L.) Walp in Mount Merapi National Park after the 2010 eruption. The methods used for root infection analysis were slide methods and root staining, while spore analysis was wet sieving methods. The results showed the highest percentage of AMF infection in C. mucunoides root was found in an area with moderate damage. The highest percentage of AMF infection in V. unguiculata was found in an area with minor damage. The highest number of spores in the two plants' rhizosphere soil was found in an area with minor damage with an average of 10.4 and 9. The levels of damage by Mount Merapi's eruption did not significantly affect the percentage of AMF infection and the number of spores. Glomus dominates all study sites in both plants. Soil organic carbon is one of the abiotic factors correlated with the number of spores in rhizosphere soil.

Mycorrhizae and a soil ameliorant on improving the characteristics of sandy soil

<p>Agricultural constraints on sandy soil are poor chemical characteristics and low biological activity resulting in the soil becoming less productive to be planted. One of the efforts to improve the quality of sandy soil are application of mycorrhizae and a soil ameliorant. The purpose of this study was to determine the effect of mycorrhizae and a soil ameliorant on soil chemical characteristics and soil biological activity. The experiment was arranged using a Complete Randomized Design that had two factors. The first factor (1) was mycorrhizae dose, without mycorrhizae (M0) and six spores of mycorrhizae/plant (M1), and the second factor (2) was types of soil ameliorant, without ameliorant (S0), cow dung (S1), rock phosphate (S2), biochar (S3), cow dung–rock phosphate (S4), cow dung–biochar (S5), and rock phosphate–biochar (S6). The results indicated that combination of six spores mycorrhizae/plant–cow dung 60 tons ha⁻¹–biochar 25 tons ha⁻¹ (M1S5) increased soil organic carbon (SOC) (235%), available P (675%), cation exchange capacity (CEC) (216%), total glomalin (101%), and easily extracted glomalin (69%), decreased exchangeable sodium percentage (66%), and increased absolutely for root infection and spore density than without mycorrhizae and a soil ameliorant (control). The lowest of SOC in non-mycorrhizae and rock phosphate, available P, CEC, root infection, spore density were found on the control, but the lowest of total glomalin and easily extracted glomalin were found on non-mycorrhizae–rock phosphate. The application of mycorrhizae, cow dung, and biochar improved the sandy soil characteristics.</p>

Rhizobial Exopolysaccharides: Genetic Regulation of Their Synthesis and Relevance in Symbiosis with Legumes

Rhizobia are soil proteobacteria able to engage in a nitrogen-fixing symbiotic interaction with legumes that involves the rhizobial infection of roots and the bacterial invasion of new organs formed by the plant in response to the presence of appropriate bacterial partners. This interaction relies on a complex molecular dialogue between both symbionts. Bacterial N-acetyl-glucosamine oligomers called Nod factors are indispensable in most cases for early steps of the symbiotic interaction. In addition, different rhizobial surface polysaccharides, such as exopolysaccharides (EPS), may also be symbiotically relevant. EPS are acidic polysaccharides located out of the cell with little or no cell association that carry out important roles both in free-life and in symbiosis. EPS production is very complexly modulated and, frequently, co-regulated with Nod factors, but the type of co-regulation varies depending on the rhizobial strain. Many studies point out a signalling role for EPS-derived oligosaccharides in root infection and nodule invasion but, in certain symbiotic couples, EPS can be dispensable for a successful interaction. In summary, the complex regulation of the production of rhizobial EPS varies in different rhizobia, and the relevance of this polysaccharide in symbiosis with legumes depends on the specific interacting couple.

In-depth evaluation of root infection systems using the vascular fungus Verticillium longisporum as soil-borne model pathogen

Background While leaves are far more accessible for analysing plant defences, roots are hidden in the soil, leading to difficulties in studying soil-borne interactions. Inoculation strategies for infecting model plants with model root pathogens are described in the literature, but it remains demanding to obtain a methodological overview. To address this challenge, this study uses the model root pathogen Verticillium longisporum on Arabidopsis thaliana host plants and provides recommendations for selecting appropriate infection systems to investigate how plants cope with root pathogens. Results A novel root infection system is introduced, while two existing ones are precisely described and optimized. Step-by-step protocols are presented and accompanied by pathogenicity tests, transcriptional analyses of indole-glucosinolate marker genes and independent confirmations using reporter constructs. Advantages and disadvantages of each infection system are assessed. Overall, the results validate the importance of indole-glucosinolates as secondary metabolites that limit the Verticillium propagation in its host plant. Conclusion Detailed assistances on studying host defence strategies and responses against V. longisporum is provided. Furthermore, other soil-borne microorganisms (e.g., V. dahliae) or model plants, such as economically important oilseed rape and tomato, can be introduced in the infection systems described. Hence, these proven manuals can support finding a root infection system for your specific research questions to further decipher root-microbe interactions.

Rhizobial Exopolysaccharides: Genetic Regulation of Their Synthesis and Relevance in Symbiosis With Legumes

Rhizobia are soil proteobacteria able to engage in a nitrogen-fixing symbiotic interaction with legumes which involves root rhizobial infection and bacterial invasion of new organs formed by the plant in response to the presence of appropriate bacterial partners. This interaction relies on a complex molecular dialogue between both symbionts. Bacterial N-acetyl-glucosamine oligomers called Nod factors are indispensable in most cases for early steps of the symbiotic interaction. In addition, different rhizobial surface polysaccharides, such as exopolysaccharides (EPS), may also be symbiotically relevant. EPS are acidic polysaccharides located out of the cell with little or no cell association that carry out important roles both in free-life and in symbiosis. EPS production is very complexly modulated and, frequently, co-regulated with that of Nod factors, but the type of co-regulation varies depending on the rhizobial strain. Many studies point out a signalling role of EPS-derived oligosaccharides in root infection and nodule invasion but, in certain symbiotic couples, EPS can be dispensable for a successful interaction. In summary, the complex regulation of the production of rhizobial EPS varies in different rhizobia and the relevance of this polysaccharide in symbiosis with legumes depends on the specific interacting couple.

Taxonomic composition and incidence of phytopathogenic fungi on the roots of soft spring wheat in the Kansk-Krasnoyarsk forest-steppe

The taxonomic composition and incidence of phytopathogenic fungi on the roots of soft spring wheat Triticum aestivum L. of nine varieties of Siberian origin (Altayskaya 70, Altayskaya 75, Krasnoyarskaya 12, Novosibirskaya 15, Novosibirskaya 16, Novosibirskaya 29, Novosibirskaya 31, Novosibirskaya 41 and Svirel) cultivated using wheat and fallow as a predecessor, was studied in the area of Kansk-Krasnoyarsk forest-steppe. Average incidence of fungal root infection was 24%. In plants grown using wheat as a predecessor, the incidence was statistically significantly (p <0.05) higher than in plants grown using fallow as a predecessor (27.3 versus 20.6%). Statistically significant (p <0.05) differences in the prevalence of root infection were revealed between cultivars. The maximal prevalence (33.3 and 32.3%, respectively) on average for the wheat predecessor and fallow was found for the varieties Svirel and Altayskaya 75, the minimal (16.7%) for the varieties Novosibirskaya 16 and Altayskaya 70. The complex of phytopathogenic fungi on the roots is represented by Fusarium spp., Bipolaris sorokiniana and Alternaria spp. (31.4, 44.9 and 23.7% of the pathogenic complex on average for varieties and variants, respectively). The composition of pathogens statistically significantly (p <0.01) depends on the predecessor. In the plants cultivated using wheat as a predecessor, the proportion of Alternaria spp. was higher whereas proportions of Fusarium spp. and Bipolaris sorokiniana were lower. No differences in prevalence and taxonomic composition of root infection between varieties originated from Novosibirsk territory, Krasnoyarsk territory and Altay territory were found. Keywords: SPRING WHEAT, ROOT ROT, KRASNOYARSK TERRITORY, FUSARIUM SPP., BIPOLARIS SOROKINIANA, ALTERNARIA SPP

Respon Pertumbuhan Tanaman Iler (Coleus scutellarioides (L.) Benth) pada Kondisi Cekaman Kekeringan terhadap Inokulasi Fungi Mikoriza Arbuskular (FMA)

Iler plant (Coleus artopurporeus L benth) is a plant that was originally cultivated as an ornamental plant and then developed as a medicinal plant because it contains flavonoids and anthocyanins. Drought stress is a major environmental problem that causes various changes in plant morphological, metabolic and physiological functions. Utilization of Arbuscular Mycorrhizal Fungi (AMF) is an effort to support the growth and development of iler plants in drought stress conditions. This study aims to determine the effect of AMF inoculation on the growth of iler plants under drought stress conditions, determine the optimal level of drought stress for ilher plant growth, and determine the best interaction between AMF inoculation and the level of drought stress on the growth of iler plants. The design used in this study was a completely randomized factorial 2-factor design. The first factor is AMF inoculation consisting of 2 levels, namely, without administration of AMF inoculum and AMF inoculum administration. The second factor is drought stress consists of 3 levels namely, 100% field capacity, 90% drought stress, and 45% drought stress. The results showed the effectiveness of the AMF inoculum test was able to increase the growth of iler plants based on parameters plant height, number of leaves, number of branches, leaf area, root length, root volume, root dry weight, number of spores and root infection. The optimal level of drought stress for iler plant growth is 90% drought stress, it is based on the parameters of plant height, number of leaves, number of branches, leaf area, root length, number of spores and root infection. There is the best interaction between AMF inoculation and 90% drought stress level on the growth of iler plants. These interactions can increase plant height, leaf area, number of spores and root infection. Keywords: arbuscular mycorrhizal fungi (FMA), drought stress, iler plants

Induced Local and Systemic Defense Responses in Tomato Underlying Interactions Between the Root-Knot Nematode Meloidogyne incognita and the Potato Aphid Macrosiphum euphorbiae

Plants mediate interactions between different herbivores that attack simultaneously or sequentially aboveground (AG) and belowground (BG) organs. The local and systemic activation of hormonal signaling pathways and the concomitant accumulation of defense metabolites underlie such AG-BG interactions. The main plant-mediated mechanisms regulating these reciprocal interactions via local and systemic induced responses remain poorly understood. We investigated the impact of root infection by the root-knot nematode (RKN) Meloidogyne incognita at different stages of its infection cycle, on tomato leaf defense responses triggered by the potato aphid Macrosiphum euphorbiae. In addition, we analyzed the reverse impact of aphid leaf feeding on the root responses triggered by the RKN. We focused specifically on the signaling pathways regulated by the phytohormones jasmonic acid (JA), salicylic acid (SA), abscisic acid (ABA), and indole-3-acetic acid (IAA) as well as steroidal glycoalkaloids as induced defense compounds. We found that aphid feeding did not induce AG hormonal signaling, but it repressed steroidal glycoalkaloids related responses in leaves, specifically when feeding on plants in the vegetative stage. Root infection by the RKN impeded the aphid-triggered repression of the steroidal glycoalkaloids-related response AG. In roots, the RKN triggered the SA pathway during the entire infection cycle and the ABA pathway specifically during its reproduction stage. RKN infection also elicited the steroidal glycoalkaloids related gene expression, specifically when it was in the galling stage. Aphid feeding did not systemically alter the RKN-induced defense responses in roots. Our results point to an asymmetrical interaction between M. incognita and Ma. euphorbiae when co-occurring in tomato plants. Moreover, the RKN seems to determine the root defense response regardless of a later occurring attack by the potato aphid AG.