R. A. Plowright

Bio: R. A. Plowright is an academic researcher from International Institute of Minnesota. The author has contributed to research in topics: Root-knot nematode & Infestation. The author has an hindex of 3, co-authored 3 publications receiving 280 citations.

Effect of Meloidogyne graminicola (Nematoda) on the establishment, growth and yield of rice cv. IR36.

Abstract: Rice cv IR36 was severely damaged by the rice root knot nematode Meloidogyne graminicola in pot experiments representing upland conditions. A high initial population density (Pi) of 80 second stage juveniles (J2)/ml of soil caused seedling death at 10 days after sowing; 80 % of seedlings had died after 32 days. The relationship between yield and Pi is described by the equation Y = Ymin + (1-Ymin)z P ; where the relative minimum yield (Ymin) = 0.05 and the term z = 0.3. The low value of z is consistent with a rapid generation time and severe early damage. The fecundity of females was inversely related to Pi.

The Induction of Phenolic Compounds in Rice After Infection By the Stem Nematode Ditylenchus Angustus

Abstract: Changes in the phenolic profiles of five resistant and two suspectible varieties of deep water rice were examined following infection by the rice stem nematode Ditylenchus angustus. Within resistant cultivars, inoculated plants were either symptomless or exhibited symptoms of incompatible (resistant), compatible (suspectible) or partially compatible responses. Extracts of leaf tissues from inoculated and uninoculated plants were made in methanol (80% v/v) and analysed by reverse phase HPLC. Tissues from inoculated plants with and without symptoms were examined separately. Traces revealed the presence of 13 to 18 UV absorbing constituents of rice leaf extracts, depending on the variety. Chlorogenic acid occurred in small amounts and only in resistant plants, but there was no correlation between constitutive compounds and resistance or susceptibility. The secondary chemistry of tissues exhibiting symptoms changed in all resistant varieties. Levels of chlorogenic acid increased in response to infection. Furthermore in two resistant selections of rice variety Rayada 16-06, a newly formed compound, the rice phytoalexin sakuranetin was also isolated. There was correlative evidence that both of these compounds could have a functional role in resistance. At 5 days after inoculation the concentrations of sakuranetin in Rayada 16-06 were 8 & 13 μg/g leaf in plants with 10 and 200 D. angustus/plant, respectively. No change in secondary chemistry occurred in susceptible varieties.

Current Nematode Threats to World Agriculture

Abstract: Many genera and species of nematodes attack almost all crops affecting their yield potential. Their distribution, diversity and potential damage depend on many factors including their centres of origin and subsequent spread, the agroecological conditions and the tolerance and resistance of the crops used in that agricultural system.

The Jasmonate Pathway Is a Key Player in Systemically Induced Defense against Root Knot Nematodes in Rice

Abstract: Complex defense signaling pathways, controlled by different hormones, are involved in the reaction of plants to a wide range of biotic and abiotic stress factors. We studied the ability of salicylic acid, jasmonate (JA), and ethylene (ET) to induce systemic defense in rice (Oryza sativa) against the root knot nematode Meloidogyne graminicola. Exogenous ET (ethephon) and JA (methyl jasmonate) supply on the shoots induced a strong systemic defense response in the roots, exemplified by a major up-regulation of pathogenesis-related genes OsPR1a and OsPR1b, while the salicylic acid analog BTH (benzo-1,2,3-thiadiazole-7-carbothioic acid S-methyl ester) was a less potent systemic defense inducer from shoot to root. Experiments with JA biosynthesis mutants and ET-insensitive transgenics showed that ET-induced defense requires an intact JA pathway, while JA-induced defense was still functional when ET signaling was impaired. Pharmacological inhibition of JA and ET biosynthesis confirmed that JA biosynthesis is needed for ET-induced systemic defense, and quantitative real-time reverse transcription-polymerase chain reaction data revealed that ET application onto the shoots strongly activates JA biosynthesis and signaling genes in the roots. All data provided in this study point to the JA pathway to play a pivotal role in rice defense against root knot nematodes. The expression of defense-related genes was monitored in root galls caused by M. graminicola. Different analyzed defense genes were attenuated in root galls caused by the nematode at early time points after infection. However, when the exogenous defense inducers ethephon and methyl jasmonate were supplied to the plant, the nematode was less effective in counteracting root defense pathways, hence making the plant more resistant to nematode infection.

Disease complexes involving plant parasitic nematodes and soilborne pathogens

Abstract: This review discusses the mechanisms underlying synergistic interactions between phytophagous nematodes and soilborne pathogens, and identifies biotic and abiotic factors affecting these interactions. Approaches towards the resolution and management of nematode‐pathogen complexes are considered and discussed.