Chitosan and EDTA conjugated graphene oxide antinematodes in Eggplant: Toward improving plant immune response.

A new strategy regarding the fabrication of chitosan (CS) or ethylene diamine tetraacetic acid (EDTA) on graphene oxide (GO) was performed. The nematocidal potential against Meloidogyne incognita causing root-knot infection in eggplant was tested. The plant immune response was investigated through measuring the photosynthetic pigments, phenols and proline contents, oxidative stress, and antioxidant enzymes activity. Results indicating that, the treatment by pure GO recorded the most mortality percentages of M. incognita 2nd juveniles followed by GO-CS then GO-EDTA. In vivo greenhouse experiments reveals that, the most potent treatment in reducing nematodes was GO-CS which recorded 85.42%, 75.3%, 55.5%, 87.81%, and 81.32% in numbers of 2nd juveniles, galls, females, egg masses and the developmental stage, respectively. The highest chlorophyll a (104%), chlorophyll b (46%), total phenols (137.5%), and free proline (145.2%) were recorded in GO-CS. The highest malondialdehyde (MDA) value was achieved by GO-EDTA (7.22%), and hydrogen peroxide (H2O2) content by 47.51% after the treatment with pure GO. Treatment with GO-CS increased the activities of catalase (CAT) by 98.3%, peroxidase (POD) by 97.52%, polyphenol oxidase (PPO) by 113.8%, and superoxide dismutase (SOD) by 42.43%. The synthesized nanocomposites increases not only the nematocidal activity but also the plant systematic immune response.

Genome-Enabled Phylogeographic Investigation of the Quarantine Pathogen Ralstonia solanacearum Race 3 Biovar 2 and Screening for Sources of Resistance Against Its Core Effectors.

Phylogeographic studies inform about routes of pathogen dissemination and are instrumental for improving import/export controls. Genomes of 17 isolates of the bacterial wilt and potato brown rot pathogen Ralstonia solanacearum race 3 biovar 2 (R3bv2), a Select Agent in the United States, were thus analyzed to get insight into the phylogeography of this pathogen. Thirteen of fourteen isolates from Europe, Africa, and Asia were found to belong to a single clonal lineage while isolates from South America were genetically diverse and tended to carry ancestral alleles at the analyzed genomic loci consistent with a South American origin of R3bv2. The R3bv2 isolates share a core repertoire of 31 type III-secreted effector genes representing excellent candidates to be targeted with resistance genes in breeding programs to develop durable disease resistance. Toward this goal, 27 R3bv2 effectors were tested in eggplant, tomato, pepper, tobacco, and lettuce for induction of a hypersensitive-like response indicative of recognition by cognate resistance receptors. Fifteen effectors, eight of them core effectors, triggered a response in one or more plant species. These genotypes may harbor resistance genes that could be identified and mapped, cloned, and expressed in tomato or potato, for which sources of genetic resistance to R3bv2 are extremely limited.

Effect of mixture of Trichoderma isolates on biochemical parameters in leaf of Macrophomina phaseolina infected brinjal.

A mixture of Trichoderma harzianum NBRI-1055 (Fx) and T. harzianum BHU-99 (Th) was evaluated for their efficiency to induce systemic resistance during three way interaction among brinjal-Trichoderma-Macrophomina phaseolina. Total phenol content (TPC), defence related enzymes Phenylalanine ammonia-lyase (PAL), Peroxidase (PO), Polyphenol oxidase (PPO) and PR proteins (PR-2 and PR-3) were recorded. Total phenolic content was recorded 12.82 times and 1.8 times higher in Trichoderma mixture treated-pathogen challenge (Fx-Th-Pth) treatment than in untreated healthy control and untreated pathogen challenged (Pth) plants respectively after 72 hr pathogen inoculation (hapi). Defence related enzymes PAL 4.54 times higher, 48hapi, PO, 3.96 times higher, 72hapi and PPO 8.1 times higher, 72hapi in Fx-Th-Pth treatment than untreated healthy control, and the PR- proteins such as PR-2, 2.15 times and PR-3, 2.16 times higher, 72hapi than untreated healthy control. The results showed that a mixture of Trichoderma (Fx+Th) performed better than single isolate.