Resistance to tomato leaf curl virus disease (ToLCVD) in tomato (Solanum lycopersicum) is scarce but was developed recently in three open pollinated (OP) varieties (Sankranthi, Nandi and Vybhav), which are now available for cultivation in South India. Hybrids with superior yield capabilities, however, are a preferred choice of cultivation by farmers but hybrids are highly susceptible to ToLCVD. In order to develop virus resistant tomato hybrids, the three OPs were crossed with 12 tomato genotypes with superior agronomic characteristics. From the crosses, 20 hybrids were selected (named BLRH-1 to BLRH-20, Bangalore leaf curl virus-resistant hybrid) and evaluated for their resistance to ToLCVD at the University of Agricultural Sciences, Bengaluru, South India, both through whiteXy-mediated inoculations in the glasshouse and natural infection in the Weld during summer 2005. Their growth and fruit yield parameters were compared against the popularly grown hybrids and OPs. DiVerences occurred between hybrids in disease incidence, spread, symptom severity and fruit yield. Of the 20 hybrids evaluated, 11 were found resistant to ToLCVD in the Weld, but only three (BLRH-3, BLRH-9 and BLRH-16) remained resistant when challenged with high virus inoculum pressure in the glasshouse through whiteXy-mediated inoculations. None of the six commercially available hybrids tested was found resistant to ToLCVD. An examination of the extent of heterosis in resistant hybrids for both quantitative and qualitative characters over the popularly grown hybrid, US-618, indicated a major improvement in virus resistance, yield and fruit quality. All the twenty hybrids yielded signiWcantly more than US-618, and of these, BLRH-3 and BLRH-16 were considered the best with yields over ca. 60 t/ha and resistant to virus both in the glasshouse and Weld.
Yellow mosaic disease caused by a Begomovirus has become an important production constraint in lima bean cultivation in Karnataka. The begomovirus causes Lima bean Yellow Mosaic Virus (LYMV), was characterized by sequencing the CP and MP genes. Distinct viral gene specific PCR product corresponding to CP and MP gene ~1000 bp and ~900 bp was obtained. The PCR product were sequenced and compared with the reference Begomoviruses sequences from the NCBI blast database. LYMV (GKVK isolate) shared highest nucleotide identity (98%) with Horsegram yellow mosaic virus (HgYMV) of French bean isolate (Accession No. AM932425.1). Phylogenetic analysis of CP and MP gene sequences of LYMV-GKVK isolate showed that LYMV-GKVK clustered with isolates of HgYMV Horsegram and French bean isolates of Tamil Nadu, Srilanka, Karnataka. Based on Nucleotide Identity begomovirus infecting lima bean at Bangalore is to be considered as strain of HgYMV. The disease was also successfully transmitted to French bean and Horsegram when experimentally transmitted using whitefly vector. Therefore, the begomovirus causing yellow mosaic disease of lima bean is considered as strain of HgYMV. Lima bean is infected by Mungbean Yellow Mosaic India Virus (MYMIV) according to earlier reports whereas our study the reports the infection of HgYMV on Lima bean from Karnataka. Thus it is concluded that Lima bean is infected by both MYMIV and HgYMV in different geographical locations.
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