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Ten different contact, systemic and combination products of fungicides were evaluated for their effectiveness against black spot of papaya Asperisporium caricae under in vitro condition by following poisoned food technique. Among fungicides tested, trifloxystrobin 25% + tebuconazole 50% WG, propiconzole 25% EC and zineb 68% + hexaconazole 4% WP were successful in completely (100%) inhibiting the growth of A. caricae at all concentrations (50,100, 250, 500, 750, 1000 ppm) which is followed by hexaconazole 25% EC, difenconazole 25% EC, zineb 68% hexaconazole 4% WP completely inhibited the growth of the fungus at 500 ppm and above concentration. Least inhibition of fungal growth was recorded in copper oxychloride 50% WP at all concentrations. Trifloxystrobin 25% + tebuconazole 50% WG, propiconazole 25% EC and zineb 68% + hexaconzole 4% WP were most effective which completely inhibited the spore germination at all concentrations, while the copper oxychloride 50% WP was recorded the least per cent inhibition of fungal spores.

Bitter gourd (Momordica charantia ) is one of the most nutritional and commercially important vegetable crops of the family cucurbitaceae. In the present study, hybrids and parents of bitter gourd were assessed to study the per se performance for yield and quality attributes. A wide range of significant variation was observed among all parents and hybrids under study. Among the parents assessed, Preethi and CO-1 was found highly significant with regard to yield attributing characters viz., fruit weight, fruit yield per plant, fruit yield ha-1 and MCM-1, MCM-2 with regard to number of fruits per plant. The hybrids CO-1 x MCM-2 followed by Preethi x MCM-1 and MCM-1 x Preethi were recorded to be the top performing hybrids for all the quantitative characters like node of first female flower appearance, days taken to first flower appearance, days to 50% flowering, fruit length(cm), fruit girth(cm), fruit weight(g), internodal length(cm), vine length(cm), sex ratio, No of seeds per fruit, No. of fruits per plant, No. of harvest and yield per plant. High ascorbic acid and iron content was recorded in parents MCM-2 and Preethi while it was found maximum in hybrids, Preethi x MCM-1, CO-1 x MCM-2 and MCM-1 X Preethi. Hence based on performance of yield and quality, the hybrids, CO-1 x MCM-2, Preethi x MCM-1 and MCM-1 x Preethi were found to be superior and can be exploited for further studies.

Banana is one of the most important fruit crops cultivated worldwide and its cultivation is hampered by infestation by nematode and Fusarium wilt complex. A pot culture experiment was conducted to study the change in biochemical constituents due to the inoculation of nematodes followed by Fusarium pathogen in select banana hybrids. The results indicated that the increase in production of defense-related compounds and enzymes such as total phenols, lignin, PO, PPO and PAL in the root tissues of inoculated plants. Among the four select banana hybrids, NPH-02-01 recorded high total phenol content (586.92 µg-1) and H 531 recorded high lignin content (1.58 %). Similarly the hybrid NPH-02-01 registered the higher activity of PO (3.5 abs.min-1.g-1), PPO (0.23 abs.min-1.g-1) and PAL (14.83 abs.min-1.g-1) when compared to other hybrids. The percentage increase of all the constituents in the hybrid NPH-02-01 was found to be comparatively higher with uninoculated plants and check cultivars.

During a field survey in Tamil Nadu (2014–16), chilli plants showing chlorotic and necrotic ring spots and necrotic streaks on leaves and stems were observed. Disease incidence ranged between 5 and 50% among five surveyed districts. RT-PCR assay using species specific primers detected 25% of samples infected with Capsicum chlorosis virus (CaCV) and 50% of samples infected with groundnut bud necrosis virus (GBNV). For simultaneous detection of CaCV and GBNV, duplex RT-PCR (dRT-PCR) has been validated. Complete nucleotide sequences of L-RNA, M-RNA, NSs and N genes of CaCV isolate (CaCV-TN-CBE) were determined.The L-RNA constitutes 8913 nt, M-RNA of 4848 nt, NSs gene of 1320 nt and the N gene of 828 nt. Sequence analysis showed that CaCV-TN-CBE isolate is closely related to China isolate based on L- and M- RNA whereas with Taiwan isolate based on S RNA. Also, based on nucleotide identity and phylogenetic analysis CaCV-TN-CBE isolate is different from the previously reported isolate from India. Further nucleotide sequences of L- and S- RNA have shown recombination events. This study suggested the isolate infecting chilli in Tamil Nadu might have evolved by undergoing recombination and reassortment evolutionary mechanisms.

Pectobacterium carotovorum subsp. carotovorum is a serious pathogen which causes soft rot or rhizome rot or tip over disease of banana in the tropical and subtropical regions of India. Rhizome rot disease incidence was severe during the secondary hardening stage in the micropropagated plantlets; prominently in the cv. Grand Naine (AAA) cultivars, effecting the initial establishment of banana plantlets in the main field. In order to combat rhizome rot disease, an experiment was conducted on biohardening of the micropropagated banana plantlets. Thirty bacterial isolates from the endophytic regions of banana were analyzed using 16S rRNA and the effective strains were identified as Bacillus subtilis. PP and CL3 strains of B. subtilis were observed to inhibit the growth of bacterial pathogen on nutrient agar. Further, crude metabolites from effective B. subtilis strains (PP and CL3), were inhibited the growth of bacterial pathogen. The endophytic Bacillus subtilis were used for biohardening of the micropropagated banana plantlets cv. Grand Naine (AAA) during the primary and secondary hardening stages. Biohardening of banana plantlets with endophytic B. subtilis significantly suppressed rhizome rot disease when treated with two strains of B. subtilis (PP and CL3) assoil application during the time of planting. Application of bacterial endophytes resulted in an increase in plant growth promotion activities viz., plant height, pseudostem girth, number of leaves and leaf area. Increased activity of defense enzymes like peroxidase (PO), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), phenolic content and PR proteins; chitinase and β-1,3-glucanase was observed in the biohardened plants that were inoculated with the bacterial antagonist.Thus, the present study demonstrated that biohardened micropropagated banana plantlets with endophytic B. Subtilis mediate the induction of systemic resistance against pathogens and could therefore be used as potential biological control agents for rhizome rot disease of tissue culture banana cv. Grand Naine (AAA).

Compared to conventional planting material, micropropagated plantlets are highly susceptible to Fusarium wilt because they are free from beneficial root inhabitants. We aimed to introduce mixtures of beneficial microbes in the plantlets in the rooting medium under in vitro conditions rather than by field applications. Endophytes and rhizobacteria from different banana cultivars and plantation areas were screened and characterized. Under in vitro conditions, banana tissue culture plantlets were bacterized with the prospective endophytes, Bacillus subtilis strain EPB56 and EPB10 and the rhizobacteria, Pseudomonas fluorescens strain Pf1 and effects of in vitro bacterization were investigated against Fusarium oxysporum f. sp. cubense race 1 under glasshouse and field conditions. Inoculation of bananas during micropropagation allowed for the omission of minerals and salts as well as vitamins from the growing media while resulting in plantlets close to double size compared to the controls with full strength media. All endophyte and rhizobacteria strains tested resulted in significant reductions in Fusarium infection in the glasshouse and field and in significantly better plant growth. The three-way combination of bacteria resulted in 78% disease reduction and more than doubled the yields compared to the untreated controls across two field experiments. Three-way inoculation led to yields of 23 and 24 kg/ bunch compared to chemical disease control (13; 15 kg/bunch) and untreated controls (10; 13 kg/bunch) in the two field experiments. Under glasshouse conditions, activity of defence enzymes was significantly increased by all inoculation treatments. Inoculation in vitro led to the establishment of the microorganisms in the plant system before delivering to the farming community. Micropropagation combined with the establishment of a beneficial microbial consortium should complement the micropropagated plants for easier adaptation under field conditions.

Field surveys were conducted during 2012–14 to document the occurrence and distribution of viruses infecting cucurbits in all the seven agroclimatic zones of Tamil Nadu state, south India. Samples collected from various types of cucurbits showing virus-like symptoms were tested for Cucumber mosaic virus (CMV), Papaya ringspot virus (PRSV), Zucchini yellow mosaic virus (ZYMV), Cucumber green mottle mosaic virus (CGMMV) and begomoviruses using serological (Dot Immuno Binding Assay, DIBA) and molecular (RT-PCR for RNA viruses and PCR for DNA viruses) methods. Results indicated higher incidence (98.6%) of begomoviruses, followed by PRSV (32.1%) and CGMMV (22.2%). ZYMV and CMV were detected at a lower frequency of 7.1% and 5%, respectively. Mixed infections with two or three of these viruses were observed in more than 50% of the samples analyzed. Sequencing of begomovirus-specific amplicons indicated the presence of sequences highly similar to Tomato leaf curl New Delhi virus (ToLCNDV) and Squash leaf curl China virus (SLCCNV).

Bud necrosis and chlorotic spots causing virus affecting chilli crop in Tamil Nadu (India) was identified as Capsicum chlorosis virus (CaCV). Specific primers were used for amplification and sequencing of the nucleocapsid protein (NP) gene. Polyclonal antibody against the bacterially expressed NP from the CaCV-TN-CBE isolate was produced using recombinant DNA technology. NP gene was subcloned into the pET-28a (+) vector and expressed by transformation in BL21 (DE3) pLysS. The expressed protein was about ∼34 kDa and was confirmed through western blot analysis using Groundnut bud necrosis virus (GBNV) polyclonal antiserum from ICRISAT, India. The purified recombinant protein was used to immunize rabbits to generate CaCV-specific polyclonal antiserum. The sensitivity levels of polyclonal antiserum thus raised was assayed through indirect ELISA or direct antigen coating (DAC)-ELISA using the recombinant protein as antigen. The recombinant antiserum produced in this study successfully detected the natural infection of CaCV on chilli plants collected from the field as well as on cowpea plants artificially inoculated with CaCV by using DAC-ELISA, DIBA and western blotting.

Solanum nigrum Linn. (Family Solanaceae) is an edible green leafy vegetable, widely consumed and cultivated on a commercial scale in southern India. It is highly prized for its medicinal properties. S. nigrum is found to harbor several groups of viruses viz., begomoviruses, orthotospoviruses, potyviruses, tobraviruses, etc., under field conditions, and therefore acts as a reservoir host. Symptoms such as mosaic mottling, crinkling, curling and distortion of leaves were observed in S. nigrum plants(cv Local) in the commercially cultivated fields of Coimbatore and Salem districts of Tamil Nadu, India during March 2016. Disease incidence ranged between 15 and 20% based on a survey conducted in ten fields each from both districts. Leaf dip preparations of symptomatic samples collected from the infected plants were analyzed by transmission electron microscopy and characteristic, typical rigid rod-shaped tobamovirus-like particles of ~300 ×18nm size were visualized. Six symptomatic leaf samples collected from 2...

Papaya (Carica papaya L.) is a popular tree crop producing flavorsome fruits rich in vitamin A and C. Recently, area under papaya has decreased due to the occurrence of Papaya ring spot virus (PRSV). None of the Carica papaya was found to have natural-resistance to PRSV-P. However, screening of germplasm for identifying the field tolerant lines of papaya was carried out with disease intensity score viz., 0-1: apparently healthy, 1-2: moderately resistant, 2-3: moderately susceptible, 3-4: susceptible, and 4 and above: highly susceptible. Among the 84 germplasm lines maintained at Horticultural College and Research Institute, accession number CP-50, a cross between Carica (Wild) × CO 6 (cultivated variety) is found to have field tolerance with disease intensity score of 1.50. The line CP-50 is a dioecious type possessing castor like leaves yielded 55.35 kg/plant in the first year and 30.17 kg in the second year.