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Suppression on plant-parasitic nematodes using a soil fumigation strategy based on ammonium bicarbonate and its effects on the nematode community.

ABSTRACT: Banana production is severely hindered by plant-parasitic nematodes in acidic, sandy soil. This study investigated the possibility of applying a novel fumigation agent based on ammonium bicarbonate as a strategy for controlling plant-parasitic nematodes under sealed conditions. Moreover, its effects on the nematode community in pot and field experiments were also measured using morphology and feeding-habit based classification and the PCR-DGGE method. Results showed that a mixture (LAB) of lime (L) and ammonium bicarbonate (AB) in suitable additive amounts (0.857?g?kg(-1) of L and 0.428?g?kg(-1) of AB) showed stronger nematicidal ability than did the use of AB alone or the use of ammonium hydroxide (AH) and calcium cyanamide (CC) with an equal nitrogen amount. The nematode community was altered by the different fumigants, and LAB showed an excellent plant-parasitic nematicidal ability, especially for Meloidogyne and Rotylenchulus, as revealed by morphology and feeding-habit based classification, and for Meloidogyne, as revealed by the PCR-DGGE method. Fungivores and omnivore-predators were more sensitive to the direct effects of the chemicals than bacterivores. This study explored a novel fumigation agent for controlling plant-parasitic nematodes based on LAB and provides a potential strategy to ensure the worldwide development of the banana industry.

SUBMITTER: Su L

PROVIDER: S-EPMC4664931 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Suppression on plant-parasitic nematodes using a soil fumigation strategy based on ammonium bicarbonate and its effects on the nematode community.

Su Lanxi L Ruan Yunze Y Yang Xiujuan X Wang Kang K Li Rong R Shen Qirong Q

Scientific reports 20151201

Banana production is severely hindered by plant-parasitic nematodes in acidic, sandy soil. This study investigated the possibility of applying a novel fumigation agent based on ammonium bicarbonate as a strategy for controlling plant-parasitic nematodes under sealed conditions. Moreover, its effects on the nematode community in pot and field experiments were also measured using morphology and feeding-habit based classification and the PCR-DGGE method. Results showed that a mixture (LAB) of lime ...[more]

PMID: 26621630

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Project description:Nitrogen (N) enrichment resulting from anthropogenic activities has greatly changed the composition and functioning of soil communities. Nematodes are one of the most abundant and diverse groups of soil organisms, and they occupy key trophic positions in the soil detritus food web. Nematodes have therefore been proposed as useful indicators for shifts in soil ecosystem functioning under N enrichment. Here, we monitored temporal dynamics of the soil nematode community using a multi-level N addition experiment in an Inner Mongolia grassland. Measurements were made three years after the start of the experiment. We used structural equation modeling (SEM) to explore the mechanisms regulating nematode responses to N enrichment. Across the N enrichment gradient, significant reductions in total nematode abundance, diversity (H' and taxonomic richness), maturity index (MI), and the abundance of root herbivores, fungivores and omnivores-predators were found in August. Root herbivores recovered in September, contributing to the temporal variation of total nematode abundance across the N gradient. Bacterivores showed a hump-shaped relationship with N addition rate, both in August and September. Ammonium concentration was negatively correlated with the abundance of total and herbivorous nematodes in August, but not in September. Ammonium suppression explained 61% of the variation in nematode richness and 43% of the variation in nematode trophic group composition. Ammonium toxicity may occur when herbivorous nematodes feed on root fluid, providing a possible explanation for the negative relationship between herbivorous nematodes and ammonium concentration in August. We found a significantly positive relationship between fungivores and fungal phospholipid fatty acids (PLFA), suggesting bottom-up control of fungivores. No such relationship was found between bacterivorous nematodes and bacterial PLFA. Our findings contribute to the understanding of effects of N enrichment in semiarid grassland on soil nematode trophic groups, and the cascading effects in the detrital soil food web.

Project description:Disease suppressive soils with specific suppression of soil-borne pathogens and parasites have been long studied and are most often of microbiological origin. As for the plant-parasitic nematodes (PPN), which represent a huge threat to agricultural crops and which successfully defy many conventional control methods, soil progression from conducive to suppressive state is accompanied by the enrichment of specific antagonistic microbial consortia. However, a few microbial groups have come to the fore in diminishing PPN in disease suppressive soils using culture-dependent methods. Studies with cultured strains resulted in understanding the mechanisms by which nematodes are antagonized by microorganisms. Recent culture-independent studies on the microbiome associated with soil, plant roots, and PPN contributed to a better understanding of the functional potential of disease suppressive microbial cohort. Plant root exudation is an important pathway determining host-microbe communication and plays a key role in selection and enrichment of a specific set of microbial antagonists in the rhizosphere as first line of defense against crop pathogens or parasites. Root exudates comprising primary metabolites such as amino acids, sugars, organic acids, and secondary metabolites can also cause modifications in the nematode surface and subsequently affect microbial attachment. A positive interaction between hosts and their beneficial root microbiota is correlated with a low nematode performance on the host. In this review, we first summarized the historical records of nematode-suppressive soils and then focused on more recent studies in this aspect, emphasizing the advances in studying nematode-microbe interactions over time. We highlighted nematode biocontrol mechanisms, especially parasitism, induced systemic resistance, and volatile organic compounds using microbial consortia, or bacterial strains of the genera Pasteuria, Bacillus, Pseudomonas, Rhizobium, Streptomyces, Arthrobacter, and Variovorax, or fungal isolates of Pochonia, Dactylella, Nematophthora, Purpureocillium, Trichoderma, Hirsutella, Arthrobotrys, and Mortierella. We discussed the importance of root exudates in plant communication with PPN and soil microorganisms, emphasizing their role in microbial attachment to the nematode surface and subsequent events of nematode parasitism. Comprehensive understanding of the plant-beneficial microbial consortia and the mechanisms underlying disease suppression may help to develop synthetic microbial communities for biocontrol of PPN, thereby reducing nematicides and fertilizers inputs.

Project description:Plant-parasitic nematodes are an important group of pests causing economic losses in agriculture worldwide. Among the plant-parasitic nematodes, the root-knot (Meloidogyne spp.) and root-lesion nematodes (Pratylenchus spp.) are considered the two most important ones affecting soybeans. In general, they damage soybean roots, causing a reduction of about one-third in productivity. The soil microbial community can exert a suppressive effect on the parasitism of plant-parasitic nematodes. Here, we investigated the effects of soil bacterial diversity on Meloidogyne javanica (Meloidogyne-assay) and Pratylenchus brachyurus (Pratylenchus-assay) suppression by manipulating microbial diversity using the dilution-to-extinction approach in two independent experiments under controlled conditions. Furthermore, we recorded the changes in the soil microbial community induced by plant-parasitic nematode infection. In Meloidogyne-assay, microbial diversity reduced the population density of M. javanica and improved plant performance. In Pratylenchus-assay, microbial diversity sustained the performance of soybean plants even at high levels of P. brachyurus parasitism. Each nematode population affected the relative abundance of different bacterial genera and altered the core microbiome of key groups within the bacterial community. Our findings provide fundamental insights into the interactions between soil bacterial diversity and plant-parasitic nematodes in soybean plants. IMPORTANCE Root-knot and root-lesion nematodes cause losses of billions of dollars every year to agriculture worldwide. Traditionally, they are controlled by using chemical nematicides, which in general have a negative impact on the environment and human health. Fortunately, the soil microbial community may suppress these pests, acting as an environmentally friendly alternative to control nematodes. However, the effects of soil microbial diversity on the parasitism of plant-parasitic nematodes still poorly understood. In this study, we provide fundamental insight into the interactions between soil bacterial diversity and plant-parasitic nematodes in soybean plants, which may be useful for the development of new strategies to control these phytopathogens.

Project description:The goal of this study was to identify bacteria involved in soil suppressiveness against the plant-parasitic nematode Heterodera schachtii. Since H. schachtii cysts isolated from the suppressive soil can transfer this beneficial property to nonsuppressive soils, analysis of the cyst-associated microorganisms should lead to the identification of the causal organisms. Our experimental approach was to identify bacterial rRNA genes (rDNA) associated with H. schachtii cysts obtained from soil mixtures with various levels of suppressiveness. We hypothesized that we would be able to identify bacteria involved in the suppressiveness by correlating population shifts with differing levels of suppressiveness. Soil treatments containing different amounts of suppressive and fumigation-induced nonsuppressive soils exhibited various levels of suppressiveness after two nematode generations. The 10%-suppressive-soil treatment contained numbers of eggs per gram of soil similar to those of the 100%-suppressive-soil treatment, indicating that the suppressive factor(s) had been transferred. Bacterial rDNA associated with H. schachtii cysts were identified using a culture-independent method termed oligonucleotide fingerprinting of rRNA genes. Bacteria from five major taxonomic groups (Actinobacteria, Cytophaga-Flexibacter-Bacteroides, alpha-Proteobacteria, beta-Proteobacteria, and gamma-Proteobacteria) were identified. Three bacterial rDNA groups contained clones that were more prevalent in the highly suppressive soil treatments than in the less suppressive treatments, indicating a potential involvement in the H. schachtii suppressiveness. When these three groups were examined with specific PCR analyses performed on H. schachtii cysts that developed in soils treated with three biocidal compounds, only one bacterial rDNA group with moderate to high sequence identity to rDNA from several Rhizobium species and uncultured alpha-proteobacterial clones was consistently associated with the highly suppressive treatments. A quantitative PCR analysis confirmed the association of this Rhizobium-like rDNA group with the H. schachtii suppressiveness.

Dataset Information

Suppression on plant-parasitic nematodes using a soil fumigation strategy based on ammonium bicarbonate and its effects on the nematode community.

Publications

Suppression on plant-parasitic nematodes using a soil fumigation strategy based on ammonium bicarbonate and its effects on the nematode community.

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