Effect of Seed-BorneSarocladium Oryzae, the Incitant of Rice Sheath Rot on Rice Seed QualityRice seeds collected fromSarocladium oryzaeinoculated plants produced more discoloured grain, chaffiness and recorded much lower seed germination than seeds collected from healthy plants in all the three cultivars tested. The germination, chaffiness and discolouration in healthy plants were found to be in the range of 70.50 to 93.50 per cent, 5.5 to 17.75 per cent and 4 to 18 per cent respectively. There was a progressive and significant reduction in total sugar, reducing sugar and non reducing sugar content of rice seeds with varying degree of seed infection caused byS. oryzaeThe increase in phenol content due toS. oryzaeinfection ranged from 15.74 to 70.78 per cent and increase being proportional to the per centS. oryzaeseed infection.

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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.

The effect of Salicylic Acid (SA) in inducing resistance in groundnut plants against Alternaria alternata was investigated. Foliar application of SA at the concentration of 1 mM significantly reduced the leaf blight disease intensity and increased the pod yield under glasshouse conditions. Changes in the activities of phenylalanine ammonium lyase, chitinase b-1,3 glucanase and in phenolic content on groundnut after application of SA and inoculation with A. alternate were studied. In SA-treated leaves (plants) an increase in phenolic content was observed five days after challenge inoculation with A. alternata in groundnut plants pretreated with SA. There was a marked increase in chitinase and pathogen inoculation in SA-treated leaves. In chitinase, b-1,3 glucanase activities were observed in response to plants with an increase in SA treated leaves. Foliar applications of SA-induced in peroxidase and polyphenol oxidase activities were observed upon challenge inoculation with pathogen.

Mushroom fungi secrete antifungal, antibacterial and antiviral bioactive compounds of therapeutic and pharmacological value. Very limited work has been done on the exploration of antimicrobial principles from macrobasidiomycetes against plant pathogens. In this view, a study was proposed to screen eight mushroom fungi viz., Auricularia polytricha, Coprinus comatus, Ganoderma lucidum, Volvariella volvaceae, Lentinus edodes, Pycnoporus sanguineus, Schizophyllum commune, Trametes versicolor against spore germination and mycelial growth of Colletotrichum capsici , the fruit rot pathogen of Chilli and to extract antimicrobial molecules from the selected mushroom fungi using different solvents viz., Chloroform, Diethyl ether and Ethyl acetate. Results from dual culture technique revealed that Ganoderma lucidum, Auricularia polytricha and Lentinus edodes showed maximum antifungal activity by inhibiting the mycelial growth of C. capsici (54.81%, 53.70 % and 45.55% respectively) with maximum inhibition zone of (4.86 mm, 2.86 mm and 4.86 mm respectively). Though the Chloroform, Diethyl ether and Ethyl acetate fractions of G. lucidum cell free extracts inhibited spore germination of C. capsici both at 12 and 24 hours, maximum inhibition of spore germination was observed at 24 hours. Among the mushroom fungi, the chloroform extracted fractions followed by Diethyl ether and Ethyl acetate fractions of G. lucidum cell free culture filtrates exhibited maximum inhibition of spore germination of C. capsici (inhibition of 88 %, 79% and 78 % respectively) at 24 hours. Similarly, maximum inhibition of mycelial growth of C. capsici with 40 %, 34.07% and 29.25 % inhibition respectively was recorded in the chloroform extracted fractions followed by Diethyl ether and Ethyl acetate fractions of G. lucidum cell free culture filtrates when compared to solvent extracted fractions of L. edodes and A. polytricha by agar well diffusion technique. The chloroform extracted metabolite of G. lucidum followed by Ethyl acetate and Diethyl ether fractions at 2000 ppm concentration inhibited maximum mycelial growth of C. capsici (60.55 %, 58.88 % and 55.47 % respectively). It is well proven that chloroform extracted fractions of G. lucidum possess antimicrobial activities against the growth of C. capsici. Hence, further studies towards the identification of these compounds will pave for development of fungicides against C .capsici.