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.
Systemically acquired resistance (SAR) and Induced systemic resistance (ISR) agents can trigger host system to produce phenolic compounds, PR proteins, sugars which impart resistance in plants against invading pathogens. The application of different concentrations of salicylic acid and Trichoderma viride (Tri-25) viz., single inoculation, combination inoculation with challenge inoculation of Exserohilum turcicum on the enhancement of growth and management of disease with special emphasis to ISR and SAR against turcicum leaf blight disease. Total phenols content were positively regulated in both the inbred lines treated with T. viride and salicylic acid in combination. In ISR, the proteins content increased from the 7 th day of sampling and in SAR, the protein contents were increased from 24 hr to 72 hr in all the treatments. The higher amount of total sugars was noticed in resistant as compared to susceptible inbred line. Total sugars, reducing sugars and non-reducing sugars were less in pathogen inoculated maize inbred lines. Chlorophyll content maximum in resistant compared to susceptible inbred line and increased over a period of time in all the treatments except in pathogen inoculation. Combination of salicylic acid and T. viride has quite long term influence on enhancement of biochemical components in host plant.
Abstract:The present study was conducted to identify the alternate hosts of new leaf curl virus disease of sunflower. In the present study several crops and weed hosts were cross inoculated with leaf curl virus of sunflower under laboratory through insect vector whitefly (Bemisia tabaci), further all inoculated samples were retested (3-4 weeks after inoculation) by molecular based Polymerse chain reaction diagnosis for the presence of virus. The results revealed that the causal virus of the disease was successfully transmitted from sunflower to sunflower (Helianthus annuus), tomato (Solanum lycopersicum) and tobacco (Nicotiana tabacum L) and weed hosts such as Acanthospermum hispidum, Amaranthus viridis and Parthenium hysterophorus in a short incubation period (2-3 weeks after inoculation), while on other hosts Chilli (Capsicum annuum L) and Datura stramonium, infection occurs in delayed incubation period. Further molecular analysis thorough polymerase chain reaction (PCR) diagnostic technique using virus specific primers also confirmed the presence of coat protein (CP) of leaf curl begomovirus in virus inoculated hosts viz., chilli, sunflower, tomato, and tobacco and weed hosts such as Acanthospermum hispidum, Amaranthus viridis, Datura stramonium and Parthenium hysterophorus. Thus, findings substantiate that the above hosts are major sources of the virus inoculum and served as potential alternate hosts of the disease during the off season.
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