Grapes downy mildew caused by obligate oomycete plant pathogen Plasmopara viticola is a devastating disease worldwide, resulting in significant yield and quality losses. A field survey was conducted in two major grapes cultivated areas of Tamil Nadu for the incidence of grapevine downy mildew. The disease incidence was 43.42%–76.69%, and the highest disease incidence of 76.69% was observed in the Theni district. Totally eight P. viticola isolates were collected from different places in Coimbatore and Theni districts. These isolates were confirmed through microscopic observation and sequencing of COX 2 gene, and the phylogenetic tree was developed to study their phylogenetic relationship among the isolates which shows 97–100% sequence similarity with other P. viticola isolates and less sequence similarity with Plasmopara species. The loop‐mediated isothermal amplification (LAMP) assay was developed based on the CesA4 gene sequence of P. viticola. The assay developed was more sensitive as it detected P. viticola genomic DNA up to 20 fmg. LAMP assay specificity was proved by carrying out the assay with genomic DNA extracted from other Oomycetes and fungal plant pathogens. Finally, LAMP assay was validated by testing seventy‐eight grapevine leaf samples collected from seven different locations. LAMP assay showed a positive reaction in sixty‐two samples tested out of seventy‐eight samples tested. Therefore, the LAMP assay described should helpful for early and specific detection of downy mildew pathogen and help in mitigating disease incidence.

Grapes powdery mildew is caused by the most destructive pathogen Erysiphe necator leading to severe yield losses around the world.  In order to study the phenotypic and molecular characters, the powdery mildew infected leaf samples were collected from eight different places in Coimbatore and Theni districts in the state of Tamil Nadu India. The identity of the pathogen as E. necator was established by microscopic studies and the isolates were further confirmed molecularly by amplification of Internal transcribed spacer (ITS) and Cytochrome b gene (Cyt b). Further molecular confirmation was obtained by characterizing Cytochrome b. An amplicon size of ~ 367 and ~ 470 bp were obtained from amplification with Uncin144 and Uncin511 and Cyt b F and Cyt b R gene primers respectively. The identity for cyt b gene segment was 96 to 98%, similarity with E. necator isolates deposited in NCBI genbank (KY418048.1, KY418049.1). A phylogenetic tree was constructed on the basis of nucleotide sequence of cytochrome b gene of the study isolates as well as E. necator and other Erysiphe species in NCBI database. From the tree it was evident that the study isolates from Tamil Nadu, India were very distinct from other E. necator isolates deposited in NCBI genbank database.

Rice is one of the most important nourishment crops providing a quarter of calories consumption. It alone contributes 23 per cent of calories consumed by people all over the world. Rice blast pathogen is an important ascomycetes fungus which causes severe yield losses up to 100 per cent under favorable climatic conditions. A field survey on rice blast disease revealed that the disease incidence was ranged from 50.1% - 72.46% with the highest disease incidence of 72.46% at Coimbatore district, Tamil Nadu, India. Totally seven isolates of Magnaporthe oryzae were collected and the identity was confirmed through morphological and molecular confirmation. A loop-mediated isothermal amplification assay was developed by targeting Pita 2 gene sequence of M. oryzae. The assay developed was more sensitive as it detected the genomic DNA of M. oryzae up to 10 fg. The specificity of LAMP assay was proved by carrying out the assay with genomic DNA extracted from other fungal pathogens. Therefore, the LAMP assay developed will be helpful in rapid, specific and sensitive detection of rice blast pathogen at field level and will help in mitigating the disease incidence.