Evaluation of strobilurin fungicides Ergon 44.3% (w/w) [Kresoxim methyl 500 g L-1 SC] and RIL-070/FI (72WP) against Phytophthora capsici infection in black pepper

Two new strobilurin fungicides viz., Ergon 44.3% (w/w) [Kresoxim methyl 500 g L-1 SC] and RIL-070/FI (72WP) were evaluated in vitro and in planta against Phytophthora capsici causing foot rot disease of black pepper and ED50 and ED90 values were calculated based on the in vitro efficacy. The chemicals were tested in planta using the maximum concentration found effective in vitro. Ergon when tested from 10-6000 ppm of the product in vitro, showed complete inhibition of mycelial growth and sporulation at 6000 ppm. But the zoospore germination was completely inhibited at 2000 ppm. The average ED50 and ED90 values of Ergon were 845.51 and 1740.71, respectively. Foliar spray of the chemical followed by challenge inoculation showed an overall reduction of lesion development by 44.83% over control and maximum inhibition (57.12%) was observed at five days after spraying at a concentration of 7000 ppm. Soil application of Ergon at different concentrations from 6000-8000 ppm showed no infection or mortality at 7000 ppm. RIL-070/FI at different concentrations from 10-500 ppm of the product when tested in vitro against P. capsici showed 100% mycelial inhibition at 50 ppm with ED50 and ED90 values of 22.85 and 45.71, respectively. For inhibition of sporulation, the maximum concentration required was 100 ppm. However, zoospore germination showed 100% reduction at 200 ppm. Foliar spraying of the RIL at concentrations from 100-600 ppm showed lesion development from 0.71 to 100%. When P. capsici was challenged five days after spraying of the chemical, 600 ppm showed 100% inhibition of lesion development. &nbsp

In vitro evaluation of fungal endophytes of black pepper against Phytophthora capsici and Radopholus similis

Experiment on in vitro screening of 125 endophytic fungi of black pepper against Phytophthora capsici indicated that 23 isolates showed more than 50% inhibition. The nematicidal activity of metabolites from endophytic fungi was also tested on Radopholus similis and the isolate BPEF73 (Daldinia eschscholtzii) showed highest mortality up to 60%. The isolates showing biocontrol potential were characterized based on internal transcribed spacer (ITS1 and ITS2) regions of rDNA. The sequence analysis of the isolates showed maximum identity with Annulohypoxylon nitens (BPEF25 and BPEF38), Daldinia eschscholtzii (BPEF41 and BPEF73), Fusarium spp. (BPEF72 and BPEF75), Ceriporia lacerata (BPEF81), Diaporthe sp. (BPEF11) and Phomopsis sp. (BPEF83). This is first report of endophytic association of above fungi in black pepper and the exploitation of their biocontrol potential against the major black pepper pathogens P. capsici and R. similis. &nbsp

Detecting and monitoring endophytic colonization by Pseudomonas putida BP25 in black pepper (Piper nigrum L.) using quantitative real-time PCR

A quantitative real-time PCR assay was developed to quantify Pseudomonas putida BP25, an antagonistic endophyte against a broad range of pathogens in black pepper such as Phytophthora capsici, Colletotrichum gloeosporioides, Rhizoctonia solani, Gibberella moniliformis, Athelia rolfsii and a plant parasitic nematode, Radopholus similis. The real-time PCR primers were designed based on the16S rRNA sequences of P. putida strains and specificity of the primers was confirmed. The detection limit of the assay was found to be 1 pg. The assay detected and quantified the bacterial colonization in the roots at weekly intervals after inoculation. The P. putida DNA was quantified to be 0.4 ng in roots corresponding to 5.4 log10 CFU g-1 at 7th and 14th day after inoculation (DAI). A decline in endophyte population was observed during 21st and 28th DAI and the DNA concentration ranged from 3.7-4.6 pg corresponding to 3.4-3.5 log10 CFU g-1 of root. No amplification could be obtained in stem and leaf samples. The newly developed real-time PCR could be useful for detection, quantification and monitoring of endophytic P. putida BP25 in different plant tissues. &nbsp

Distribution of Pythium myriotylum Drechsler causing soft rot of ginger

Fourteen of the 29 Pythium isolates pathogenic to ginger (Zingiber officinale) collected fromvarious parts of India such as Assam, Karnataka, Kerala, Sikkim and Uttar Pradesh wereidentified as Pythium myriotylum based on the size of the species-specific amplicon (150 bp)using the oligo primers Pmy5 and ITS2. The suitability of the primer combination Pmy5 (5’-gTC gCT gTT ATg gCg gAg-3’) and ITS2 (5’-gCT gCg TTC TTC ATC gAT gC-3’) (Wang et al.2003a) at the species level identification of P. myriotylum was further confirmed through thisstudy. &nbsp

Effect of extenders and sperm concentration on migration efficiency of Malabari buck spermatozoa in bovine cervical mucus

The study evaluated the effect of extenders and sperm concentration on the migration efficiency of Malabari buck spermatozoa in bovine cervical mucus. Fresh semen ejaculates collected on six different days from three adult healthy Malabari bucks were pooled and divided into four groups based on the extender used (tris-egg yolk-based or liposome-based extender) and rate of extension (200 or 400 million motile spermatozoa per 0.5 mL) (n=6 per group) and subjected to cryopreservation. After freezing and thawing, Malabari buck spermatozoa cryopreserved in liposome-based extender travelled significantly (p<0.05) greater distance in bovine cervical mucus compared to those preserved in tris-egg yolk-based extender when packed in French medium straws with 200 million progressively motile spermatozoa. The corresponding values with 400 million progressively motile spermatozoa also showed the same trend. It was also observed that Malabari buck semen extended with 200 million progressively motile spermatozoa was significantly (p<0.05) better in terms of migration efficiency in bovine cervical mucus compared to that with 400 million progressively motile spermatozoa in both the extenders

Screening of rhizobacterial isolates against soft rot disease of ginger (Zingiber officinale Rosc.)

Twenty rhizobacterial cultures including Pseudomonas fluorescens, Enterobacter agglomerans and Bacillus sp. were tested under in vitro and in vivo conditions to evaluate their efficacy in inhibiting Pythium myriotylum and reducing the incidence of soft rot disease in ginger (Zingiber officinale). Under in vitro conditions, 19 of the tested rhizobacterial cultures significantly inhibited P. myriotylum. Evaluation of these cultures under in vivo conditions indicated that seven of the isolates were effective in suppressing the pathogen. Five of the isolates when inoculated along with Glomus sp. (vesicular arbuscular mycorrhizae) also enhanced root development without disease incidence. &nbsp

Screening of black pepper (Piper nigrum L.) germplasm for resistance to foot rot disease caused by Phytophthora capsici Leonian

Studies were conducted at Calicut (Kerala) to locate sources of resistance among 491accessions of cultivars, 691 hybrids, 124 wild accessions and 182 Karimunda and 60Kottanadan selections of black pepper (Piper nigrum) using stem inoculation technique againstfoot rot disease caused by Phytophthora capsici. One hybrid (Acc. 1375), two wild accessions(Accs. 3160 and 3260) and four Kottanadan selections (2466, 2471, 2515 and 2433) werepromising with disease index 1 and no external lesion after inoculation of the pathogenunder greenhouse conditions. &nbsp

Cross species amplification of microsatellite loci from Phytophthora spp to assess genetic diversity among the Phytophthora isolates from black pepper

Phytophthora capsici&nbsp;is one of the most destructive pathogens of black pepper in India and the world over. Diversity of 114&nbsp;Phytophthora&nbsp;isolates obtained from leaf, stem, root and soil of different agro climatic areas was studied using 25 SSR primers that were previously described. twenty primers were successfully amplified. Of these, 15 were polymorphic among the&nbsp;Phytophthora&nbsp;isolates and altogether 37 loci were detected. Of the 37 bands generated from 20 primers, 75.67% were polymorphic. Cluster analysis using the unweighted pair-group method with arithmetic averages divided the isolates into seven major groups. The dendrogram generated showed that all the isolates were separated at similarity coefficient between 57-95%. Group 7 with a single isolate stood as an out group. Clustering did not follow the pattern of geographical origin or plant part from where the isolates were obtained. &nbsp

Mosaic disease of vanilla (Vanilla planifolia Andrews) - the first report from India

Recent disease surveys revealed the occurrence of a mosaic disease in vanilla. The infected plants showed mosaic symptoms, distortion of leaves, leaf curling etc. which are typical symptoms of viral infection. Negative staining of the leaf sap with potassium phosphotungstic acid, uranyl acetate and ammonium molybdate revealed the presence of flexuous rod shaped viral particles. This is the first report of occurrence of viral disease in vanilla from India. &nbsp

Economic viability of large-scale production of the biocontrol agent Trichoderma harzianum Rifai

The economic viability of large scale production of the biocontrol agent Trichoderma harzianumeffective against the soil-borne disease Phytophthora foot rot (caused by &nbsp;P. capsici) &nbsp;of blackpepper (Piper nigrum) was studied. &nbsp;The enterprise was highly profitable for the entrepreneurwith a benefit:cost ratio of 1.84. The investment returned a net present worth of Rs. 2,42,618@ 11% interest rate for 10 years period with an internal rate of return of 121%. &nbsp