Search

Mungbean is one of the important food legumes in the Indian–sub-continent. Yellow mosaic disease, caused by Mungbean yellow mosaic virus and Mungbean yellow mosaic India virus (MYMIV) poses a severe threat to its production. Agroinoculation has been the most preferred way to test the function of genomic components of these viruses. However, the available inoculation methods are not as efficient as whitefly transmission, thereby limiting their usage for screening and biological studies. We hereby report an efficient and reproducible agroinoculation method for achieving maximum (100%) efficiency using tandem repeat infectious agro-constructs of DNA A and DNA B of MYMIV. The present study targeted wounding of various meristematic tissues of root, shoot, parts of germinating seeds and also non-meristematic tissue of stem to test the suitable tissue types for maximum infection. Among the various tissues selected for, the inoculation on the epicotyl region showed maximum infectivity. Further, to enhance the infectivity of MYMIV, different concentrations of acetosyringone, incubation time and Agrobacterium cell density were also standardized. The incubation of wounded sprouted seeds in 1.0 OD of agroculture containing repeat construct of MYMIV for 2–4 h without acetosyringone followed by sowing in soil showed maximum infection of MYMIV within 10–12 days on the first trifoliate leaf. This standardized method is reproducible and has potential to screen germplasm lines and will be useful in mungbean biological/virological studies and breeding programmes. [ABSTRACT FROM AUTHOR]

Mungbean is one of the important food legumes in the Indian–sub-continent. Yellow mosaic disease, caused by Mungbean yellow mosaic virus and Mungbean yellow mosaic India virus (MYMIV) poses a severe threat to its production. Agroinoculation has been the most preferred way to test the function of genomic components of these viruses. However, the available inoculation methods are not as efficient as whitefly transmission, thereby limiting their usage for screening and biological studies. We hereby report an efficient and reproducible agroinoculation method for achieving maximum (100%) efficiency using tandem repeat infectious agro-constructs of DNA A and DNA B of MYMIV. The present study targeted wounding of various meristematic tissues of root, shoot, parts of germinating seeds and also non-meristematic tissue of stem to test the suitable tissue types for maximum infection. Among the various tissues selected for, the inoculation on the epicotyl region showed maximum infectivity. Further, to enhance the infectivity of MYMIV, different concentrations of acetosyringone, incubation time and Agrobacterium cell density were also standardized. The incubation of wounded sprouted seeds in 1.0 OD of agroculture containing repeat construct of MYMIV for 2–4 h without acetosyringone followed by sowing in soil showed maximum infection of MYMIV within 10–12 days on the first trifoliate leaf. This standardized method is reproducible and has potential to screen germplasm lines and will be useful in mungbean biological/virological studies and breeding programmes. [ABSTRACT FROM AUTHOR]

Intensive cultivation, climate change and host–pathogen dynamics/interaction had led to emergence of viral diseases and vector population, thereby causing significant economic losses. In the present study, extensive surveys were conducted (during 2016–2017) followed with field experiments (2017 and 2019 kharif and 2018 rabi seasons) in the state of Chhattisgarh, India, comprising of three diverse agroecological zones, viz., northern hill zone, central plain zone and southern Bastar plateau zone, for understanding the distribution pattern of viruses and vector populations in prominent pulses and vegetable crops. Field experiments revealed that more than 90% incidence of yellow mosaic disease (YMD) was recorded in mungbean and urdbean, followed by YMD of ridge gourd and bitter gourd, leaf curl disease of tomato (ToLCD) and chilli and yellow vein mosaic disease of bhendi; however, only five per cent YMD was recorded in cow pea. Molecular and sequence analysis of viral genomic components revealed ToLCD in central plain zone of Chhattisgarh was caused by a consortium of begomoviruses, including Tomato leaf curl New Delhi virus (ToLCNDV), Tomato leaf curl Karnataka virus (ToLCKV), and Tomato leaf curl Kerala virus associated with satellite molecules. YMD of mungbean, cow pea and soybean was caused by Mungbean yellow mosaic India virus (MYMIV), while YMD of ridge gourd was caused by ToLCNDV. PCR analysis, using species‐specific primers, of samples representing the three different regions revealed that YMD of mungbean, urdbean and cowpea was positive only for MYMIV and was unevenly distributed, while YMD of ridge gourd, bitter gourd, pumpkin and sponge gourd was positive only for ToLCNDV; however, ToLCD was positive for either ToLCNDV or ToLCKV or both, and some samples were also found associated with betasatellite molecules. Amaranthus and rice bean were identified as non‐host species for the begomoviruses infecting tomato and MYMIV, as observed by surveys in the hot‐spot‐like areas, controlled whitefly transmission as well as agroinoculation. Compilation and analysis of available information on begomoviruses affecting these crops in India suggest that they are unevenly distributed in India. This is the first report of the begomovirus occurrence in pulses and vegetable crops in this agroecologically diverse region. [ABSTRACT FROM AUTHOR]