VEMANA, K.SARATBABU, K.2022-08-172022-08-172022-08-17D6264https://krishikosh.egranth.ac.in/handle/1/5810186400STUDIES ON Tobacco streak virus (TSV) CAUSING PEANUT STEM NECROSIS DISEASE (PSND) AND ITS INTERACTION WITH Groundnut bud necrosis virus (GBNV) IN GROUNDNUT (Arachis hypogaea L.)Groundnut is an annual legume crop grown in diverse environment over the world between 40oN and 40oS. Among the viruses infecting groundnut, Tobacco streak virus (TSV) causing peanut stem necrosis disease (PSND) and Groundnut bud necrosis virus (GBNV) causing Peanut bud necrosis disease (PBND) are major constraints for groundnut cultivation in India. Extensive survey was so far not conducted in groundnut growing districts of A.P. and very limited research was carried out regarding screening of groundnut genotypes against PSND in both field and artificial conditions in glass house. Cloning of resistant gene analogues (RGA), morphological and biochemical parameters responsible for resistance against PSND in groundnut genotypes were not attempted. Further, mixed infection of TSV and GBNV, and their combined impact on groundnut cultivation have not been studied to date. In this context, diagnostic surveys were conducted to determine the incidence of viral diseases in groundnut growing districts of Andhra Pradesh (A.P). Studies on identification of resistance sources against TSV in groundnut genotypes through natural infection and artificial sap inoculation, identification of resistance to Tobacco streak virus (TSV) using resistance gene analogue in groundnut genotype and interaction of TSV and GBNV in groundnut was carried out at Agricultural Research Station, Kadiri from 2017 to 2020. Roving survey was conducted for assessing the incidence of viral diseases in 12 districts of A.P. during kharif and rabi 2017-18. Major viral diseases such as PSND and PBND was observed during the survey. Mean PSND incidence was significantly higher in kharif 2017-18 (7.4%) compared to rabi 2017-18 (6.5%) in groundnut growing districts of A.P. The present study recorded PSND incidence for the first time from four coastal A.P. districts (Krishna, Guntur, Sri Pottisriramulu Nellore, Prakasham) with confirmation using DAC-ELISA and RT-PCR. The partial coat protein (CP) gene of TSV-GN-INDVP groundnut isolate shared wide range of nucleotide identities (80.72-98.62 %) with isolates reported globally. Present study isolate shared 97.97-98.51% xiv nucleotide identities with groundnut isolates and 97.51-98.62 % nucleotide identities with other crop TSV isolates from India. Of the 70 fields surveyed, spread over twelve districts of A.P., 66 fields showed infection of GBNV revealing wide spread occurrence of the disease in A.P. Roving survey revealed that PBND incidence was significantly higher in rabi 2017-18 (13.6%) compared to kharif 2017-18 (5.3%) in groundnut growing districts of A.P. Partial nucleocapsid (N) protein gene of GBNV-GN-BPIND groundnut isolate shared high range of nucleotide identity (78.66-98.48 %) with other GBNV isolates reported from different crops and locations. GBNV-GN-BPIND isolate shared 96.67-97.73 per cent nucleotide identity with groundnut isolates and 96.59–98.48 per cent nucleotide identity with GBNV isolates of other crops from India. Sixty-two genotypes (Elite, pre-released and interspecific cross derivatives) screened against PSND for two seasons (kharif 2017-18 and kharif 2018-19) by Parthenium infector border and natural conditions (without infector border). Field screening of genotypes revealed that the genotypes ICGV-06175, ICGV-06145, ICGV-06149 and genotypes viz., K-7 bold, Kadiri Lepakshi, K-9, K-1909 performed consistently highly resistant and resistant reaction respectively in field conditions for two seasons (kharif 2017-18 and 2108-19). Above resistant genotypes along with susceptible genotypes viz., ICGV07120, K-1811, Kadiri Harithandra, Kadiri Amaravathi, K-2269 (E), K-1482K-, ICG14373, K-1628 (HY), K-2270, GPBD-4, 1501 (FDR), 1559 (FDR), Kisan were selected for further studies under glasshouse condition to confirm their resistance against TSV by mechanical sap inoculation at 14 DAS. The per cent disease incidence was recorded 3-10 days’ post inoculation (DPI) ranged from 37.5 to 100% among the genotypes. The minimum incidence was recorded in ICGV-06175 and showed significant difference with other genotypes. The genotypes grouped under highly resistant, resistant categories in field screening became susceptible in glasshouse during TSV sap inoculation. The genotypes which are given highly resistant (ICGV-06175, ICGV-06145, ICGV-06149), resistant (K-7 bold, Kadiri Lepakshi, K-9, K-1909), susceptible (Kisan) reaction under field condition were selected to isolate RGAs using PCR based approach and successfully isolated RGAs from genomic DNA of TSV highly resistant, resistant and susceptible groundnut genotypes. As compared to highly resistant and resistant genotypes, susceptible genotype showed faint band amplification and analysis of derived peptide sequences revealed that deletion of amino acid sequence in P-loop motif and expressed shift of amino acids such as aspartic acid (D) to serine (S) and leucine (L) to valine (V) in non-TIR-NBS LRR sub family when compared to resistant and tolerant genotypes. In highly resistant genotypes RGA clones viz., RGA 12 (ICGV06175) and RGA14 (ICGV06145) in TIR- NBS LRR sub family expressed shift of amino acid leucine (L) to serine (S) when compared to resistant and susceptible genotypes. During simultaneous inoculation no synergism was observed between TSV and GBNV, while a slight antagonism was observed between these viruses. But this antagonism reaction didn’t help the plant in avoiding disease. Based on reaction under high disease pressure (using Parthenium infector border) under field condition and artificial sap inoculation under glasshouse conditions the genotype ICGV06175 was identified as highly resistant against PSND and can be used in breeding program as a resistant source against PSND. The isolated RGAs from groundnut genotypes can be used for characterization of different resistant genes and can be explored in the development of disease resistance molecular markers.EnglishThesis