A field experiment was conducted to study the effect of chemical defoliation on growth parameters, seed cotton yield and economics of cotton under high density planting during kharif, 2016. Defoliation with Etherel @ 2000 ppm at 60 boll opening percentage resulted in higher number of picked bolls plant -1 and boll opening percentage and seed cotton yield (2359 kg ha -1 ). At harvest, significantly highest drymatter accumulation was recorded with Urea @ 15% (T 6 ) (22692 kg ha -1 ). Dropp Ultra 560 SC (Thidiazuron 360 + Diuron 180) @ 200 ml/ha recorded significantly higher leaf defoliation (99.7 %) and was superior over other defoliants tried. Application of defoliants i.e., Dropp Ultra and Etherel at 60 BOP resulted in reduction of crop duration by 20 days.
Two distinct emaraviruses, Pigeonpea sterility mosaic virus-I (PPSMV-I) and Pigeonpea sterility mosaic virus-II (PPSMV-II) were found to be associated with sterility mosaic disease (SMD) of pigeonpea [Cajanus cajan (L.) Millsp.]. The host range of both these viruses and their vector are narrow, confined to Nicotiana benthamiana identified through mechanical transmission, and to Phaseolus vulgaris cvs. Top Crop, Kintoki, and Bountiful (F: Fabaceae) through mite transmission. A weed host Chrozophora rottleri (F: Euphorbiaceae) was also infected and tested positive for both the viruses in RT-PCR. Among the wild Cajanus species tested, Cajanus platycarpus accessions 15661, 15668, and 15671, and Cajanus scarabaeoides accessions 15683, 15686, and 15922 were infected by both the viruses and mite vector suggesting possible sources of SMD inoculum. Though accession 15666 of C. platycarpus, 15696 of C. scarabaeoides, and 15639 of Cajanus lanceolatus were infected by both the viruses, no mite infestation was observed on them. Phylogenetic analysis of nucleotide sequences of RNA-1 and RNA-2 of PPSMV-I and PPSMV-II isolates in southern India revealed significant divergence especially PPSMV-II, which is closely related to the Fig mosaic virus (FMV) than PPSMV-I. In multilocation testing of pigeonpea genotypes for their broad-based resistance to SMD for two consecutive years, genotypes ICPL-16086 and ICPL-16087 showed resistance reaction (<10% incidence) in all three locations studied. Overall, the present study gives a clear idea about the host range of PPSMV-I and PPSMV-II, their molecular relationship, and sources of resistance. This information is critical for the development of reliable diagnostic tools and improved disease management strategies.
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