The present study was carried out at Central Potato Research Station, Shillong during 2013 and 2014 to assess the growth and yield performance of three grades of in-vitro produced micro-tubers viz. >8 mm, 4-8 mm and <4 mm of two potato (Solanum tuberosum) cultivars namely Kufri Girdhari and Kufri Megha under field planting conditions. The experiment was laid out in a randomised block design with four replications using a common spacing of 50 × 20 cm. The larger grade micro-tubers generally exhibited better physiological growth as well as yield parameters. The larger sized micro-tuber (>8 mm) showed significantly superior plant survival, canopy cover, plant height, number of compound leaves per plant, number of stems per plant and plant vigour followed by 4-8 mm grade and <4 mm grade micro-tubers. Similar trend was observed for all the yield parameters. Among varieties, Kufri Girdhari out performed Kufri Megha in all the growth and yield parameters in all the micro-tuber grades. Thus both micro-tuber size and genotype influenced the field performance. The overall finding indicates that micro-tubers irrespective of the size for both the varieties can produce mini-tubers successfully under direct field conditions in the NEH region which will facilitate quality seed production.
Severe incidence of a mosaic disease was observed on summer squash (Cucurbita pepo), commonly called pepo, grown in Varanasi during June-September of Khariff season 2007. Symptoms observed were mosaic, puckering on the leaves, wartiness on fruits, general stunting of plants and low yield. PCR amplification with degenerate primers designed to target the conserved sequences of coat protein gene of whitefly transmitted geminiviruses showed *800 bp fragment in all symptomatic samples tested, indicating the association of a geminivirus with the disease. Nucleotide sequence analysis of the amplified fragment showed 99% identity with pumpkin isolate of squash leaf curl china virus (SLCCNV) from Lucknow. It showed 85-96.7% homology with other isolates of SLCCNV from India and abroad. Phylogenetic analysis revealed the isolate on pepo from Varanasi clustered with SLCCNV isolates on pumpkin from Lucknow and Coimbatore.
In developing a Trichoderma viride-based biocontrol program for Fusarium wilt disease in chickpea, the choice of the quality formulation is imperative. In the present study, two types of formulations i.e. powder for seed treatment (TvP) and tablet for direct application (TvT), employing T. viride as the biocontrol agent, were evaluated for their ability to control chickpea wilt under field conditions at three dosages i.e. recommended (RD), double of recommended (DD) and half of recommended (1/2 RD). A screening study for the antagonistic fungi strains based on volatile and non-volatile bioassays revealed that T. viride ITCC 7764 has the most potential among the five strains tested (ITCC 6889, ITCC 7204, ITCC 7764, ITCC 7847, ITCC 8276), which was then used to develop the TvP and TvT formulations. Gas Chromatography-Mass Spectrometry (GC-MS) analysis of volatile organic compounds (VOCs) of T. viride strain confirmed the highest abundance of compositions comprising octan-3-one (13.92%), 3-octanol (10.57%), and 1-octen-3-ol (9.40%) in the most potential T. viride 7764. Further Physico-chemical characterization by standard Collaborative International Pesticides Analytical Council (CIPAC) methods revealed the optimized TvP formulation to be free flowing at pH 6.50, with a density of 0.732 g cm-3. The TvT formulation showed a pH value of 7.16 and density of 0.0017 g cm-3 for a complete disintegration time of 22.5 min. The biocontrol potential of TvP formulation was found to be superior to that of TvT formulation in terms of both seed germination and wilt incidence in chickpea under field conditions. However, both the developed formulations (TvP and TvT) expressed greater bioefficacy compared to the synthetic fungicide (Carbendazim 50% WP) and the conventional talc-based formulation. Further research should be carried out on the compatibility of the developed products with other agrochemicals of synthetic or natural origin to develop an integrated disease management (IDM) schedule in chickpea.
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