Genomic regions associated with resistance to Fusarium wilt in castor identified through linkage and association mapping approaches.

Fusarium wilt, caused by Fusarium oxysporum f. sp. ricini, is the most destructive disease in castor. Host plant resistance is the best strategy for the management of wilt. Identification of molecular markers linked to wilt resistance will enhance the efficiency and effectiveness of breeding for wilt resistance. In the present study, genomic regions linked to wilt resistance were mapped using a bi-parental population of 185 F6-RILs and a genetically diverse panel of 300 germplasm accessions. Quantitative trait loci (QTL) analysis performed using a linkage map consisting of 1090 SNP markers identified a major QTL on chromosome 7 with an LOD score of 18.7, which explained 44% of the phenotypic variance. The association mapping performed using genotypic data from 3465 SNP loci revealed 69 significant associations (p < 1 × 10-4) for wilt resistance. The phenotypic variance explained by the individual SNPs ranged from 0.063 to 0.210. The QTL detected in the bi-parental mapping population was not identified in the association analysis. Thus, the results of this study indicate the possibility of vast gene diversity for Fusarium wilt resistance in castor.

A novel chitosan biopolymer based Trichoderma delivery system: Storage stability, persistence and bio efficacy against seed and soil borne diseases of oilseed crops.

Management of seed and soil borne fungal plant pathogens using fungal species belonging to the genus Trichoderma is gaining importance. Seed coating with powder based formulations of Trichoderma is most widely adopted by the researchers and farmers as well. Delivery system that leads to good adherence of fungal propagules on seed surface, minimizing the wastage of active ingredient, sustained and timely release during treatment process is very important for effective season long protection. Chitosan-PEG (Polyethylene glycol) (Cts-PEG) blend containing Trichoderma harzianum (Th4d) (Cts-PEG-Th) spores is developed and its storage stability, persistence in soil and bio efficacy against seed and soil borne pathogens of groundnut and safflower crops is studied. The blend was stable without much changes in pH throughout the storage period. Persistence studies conducted for 3 months revealed that Cts-PEG-Th amended soil, Trichoderma got released from polymer film slowly and reached a maximum of log 8 CFUs by 30 days and there after started declining to retain log 6 CFUs at 90 days. In shelf life study, the chitosan blend was able to maintain Trichoderma counts of log 10.0 and log 10.2 over a period of 6 months at storage temperatures of 30 °C and 4 °C, respectively and the antagonistic activity unaffected against three plant pathogens viz. Macrophomina phaseolina, Fusarium oxysporumf. sp.ricini and Aspergillus niger over a period of 6 months of storage. Bio efficacy testing in germination towels and green house pot studies revealed the effectiveness of seed treatment with Cts-PEG-Th blend significantly increasing the germination and seedling vigour and reducing the diseases in groundnut (peanut) and safflower.

Development of chitosan-PEG blended films using Trichoderma: Enhancement of antimicrobial activity and seed quality.

Fungi under genus Trichoderma as ameliorates of biotic and abiotic stresses in cultivated crops is gaining popularity world-wide and their application in conjunction with seed coating polymers is an attractive proposition to reduce bioagent wastage and harnessing benefits of combined application. The synergistic action of Trichoderma with natural polymers like chitosan can enhance antimicrobial activity. A series of blended film solutions were synthesized by using chitosan, PEG and plasticizer in varying concentrations. The optimization of blended film composition and dose for coating of seeds was done w.r.t seed coating. Studies on compatibility of film forming ingredients with Trichoderma have not shown any inhibition and antimicrobial activity has shown different levels of inhibition of plant pathogens. Films were structurally characterized by XRD, SEM, FT-IR, TGA, DSC. The optimized film solution in combination with different Trichoderma strains improved seed quality parameters in test crop castor (Ricinus communis). Significant increase in vigour index (3110) was observed with Th4d treatment followed by chitosan and Th4d combination formulation (3023). In conclusion, the optimized chitosan-PEG-Th blend was effective in enhancing seed germination and plant growth of castor. The material can be further tested under large field evaluation as a seed coating agent against various plant diseases.

Tricalcium phosphate solubilizing abilities of Trichoderma spp. in relation to P uptake and growth and yield parameters of chickpea (Cicer arietinum L.).

Nine isolates of Trichoderma spp. were investigated for their ability to solubilize insoluble phosphate in Pikovskaya's broth and were compared with an efficient phosphate-solubilizing bacterium Bacillus megaterium subsp. phospaticum PB that was used as the reference strain. All 9 Trichoderma isolates were found to solubilize insoluble tricalcium phosphate to various extents. Trichoderma viride (TV 97) (9.03 microg x mL(-1)), Trichoderma virens (PDBCTVs 12) (9.0 microg x mL(-1)), and Trichoderma virens (PDBCTVs 13) (8.83 microg x mL(-1)) solubilized 70% of that solubilized by the reference strain Bacillus megaterium (12.43 microg x mL(-1)). Pot culture and field evaluations with Trichoderma harzianum (PDBCTH 10), Trichoderma viride (TV 97), and Trichoderma virens (PDBCTVs 12) using chickpea (Cicer arietinum L.) 'Annegeri-1' as the test plant and rock phosphate as the phosphorus source showed significantly increased P uptake in plants treated with Trichoderma harzianum (PDBCTH 10) followed by Trichoderma virens (PDBCTVs 12) and Trichoderma viride (TV 97). Inoculation of Trichoderma spp. also showed increased growth and yield parameters of chickpea compared with the uninoculated controls under both glasshouse and field conditions.

First Report of Tobacco streak virus Infecting Safflower (Carthamus tinctorius) in Maharashtra, India.

Safflower, Carthamus tinctorius L. (Asteraceae), is extensively cultivated in India, China, and other parts of Asia for edible oil, dyeing agent, and its medicinal value. In 2003, safflower entry (NARI-6) in the All-India Coordinated Research Project on Oilseeds (Safflower) grown in the experimental fields of M/s Syngenta India Ltd., Aurangabad (Maharashtra State, India) exhibited symptoms of veinal and leaf necrosis, necrotic streaks on the stem, necrosis of the terminal bud, and ultimately plant death. The disease was attributed to Tobacco streak virus (TSV) because sunflower growing adjacent to safflower showed similar symptoms caused by TSV (1). Mechanical inoculations of sap from symptomatic safflower leaves caused typical symptoms of TSV (local, irregular, necrotic rings, veinal necrosis, and systemic veinal necrosis) on Vigna unguiculata (L.) Walp. cv. C-152 and Phaseolus vulgaris (L.) cv. Topcrop, and symptoms of local, necrotic lesions, veinal necrosis, and systemic necrosis of leaf and growing bud on Arachis hypogaea L. cv. JL-24. Sap-inoculated safflower cv. Manjeera showed chlorotic and necrotic local lesions followed by systemic leaf necrosis, leading to necrosis and death of the terminal bud. Safflower cvs. A-1, BIP-2, Co-1, and Bheema (10 plants of each cultivar) inoculated with sap from safflower plants showing typical TSV symptoms did not show any visible symptoms except stunting, but six to nine plants of each cultivar tested positive for TSV using enzyme-linked immunosorbent assay (ELISA) tests. In direct antigen coating-ELISA, the virus reacted positively with antiserum produced to an isolate of TSV from peanut (2) and to antiserum to TSV (ATCC-PVAS 276 for Datura stramonium), but did not react to peanut bud necrosis tospovirus antiserum. Examination of leaf extracts using leaf-dips and immunosorbent electron microscopy with the antiserum of TSV-peanut isolate showed isometric particles resembling those in the genus Ilarvirus. To our knowledge, this is the first report of an isolate of Tobacco streak virus infecting safflower. References: (1) R. D. V. J. Prasada Rao et al. J. Oilseeds Res. 17:400, 2000. (2) A. S. Reddy et al. Plant Dis. 86:173, 2002.

Bilateral renal agenesis in two litters of Shetland sheepdogs.

Two cases of bilateral renal agenesis (1 pup from each of 2 related bitches) were observed in a purebred Shetland sheepdog breeding colony. Gross postmortem and histopathologic examinations confirmed a diagnosis of bilateral renal agenesis as the cause of death. Limited available data strongly suggests an inherited etiology for bilateral renal agenesis. (Editor's Note: This report is published as an example of a situation where circumstantial evidence suggested a cause-and-effect relationship between the change in heartworm medication and the anomalies. Careful scientific data collection and review avoided falling into that trap and identified the genetic basis for the observed defects.