Global positioning system based spatial and temporal distribution of new leaf curl begomovirus disease on sunflower in Northern Karnataka

Leaf curl disease on sunflower caused by begomovirus genus of the family geminiviridae. Present investigations on field survey for disease incidence, field diagnostic symptoms and its spatial and temporal distribution in major sunflower growing parts of North Eastern Karnataka through GPS system during 2013-14, revealed that the disease was found to occur at all the stages of sunflower under field condition and exhibited symptoms such as vein thickening (enations) on abaxial surface of the leaves, upward curling and reduction in leaf size and severe discoluration of capitulum (Head) followed by bushy appearance. GPS based survey indicated that the % disease incidence varied from location to location (spatial variation) and also from season to season (temporal variation). The low incidence was noticed during Kharif condition which is ranged between 6.34-11.16, with the average incidence of 11.2%, 7.4% and 6.3% in Koppal, Raichur and Ballari districts repectively. Whereas during Rabi/summer season, high magnitude of disease noticed in many of the locations surveyed and is recorded upto 92.9 %. The GPS maps plotted based on PDI scale (0-3) represents high risk areas of the disease in Raichur and adjacent areas of Nort Eastern Karnataka and the result shows that the disease occurrence was more in rabi as compared to Kharif situations irrespective of locations. GPS survey map is an indicator to locate the nature of disease spread so as to conclude the hotspot areas

Biological and molecular evidences on host range of leaf curl begomovirus disease of sunflower (Helianthus annuus L.)

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 invirus 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