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2019 - 201912020 - 20231
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Author: Belludi, Rakesh × Type: Thesis ×
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    Detection, variability and translocation of Potato virus Y (PVY) infecting potato in Punjab and identification of host plant resistance
    (Punjab Agricultural University, 2023) Belludi, Rakesh; Sharma, Abhishek
    This study aimed to investigate the variability of Potato virus Y (PVY) infecting potato crop of Rabi season in Punjab, encompassing symptomatology, serology and molecular aspects. The study revealed prevalent symptoms, such as mild mosaic, chlorotic patches, interveinal chlorosis, puckering, veinal necrosis and stem necrosis, on potato plants caused by various potato viruses including PVY. ELISA tests confirmed the presence of six out of seven viruses in potato samples. Among them, PVX exhibited the highest incidence (78.08%), followed by PVYN (51.37%), PVM (20.55%), PVYO/C and PVS (13.01%). PLRV exhibited a lower incidence (2.74%) and no samples tested positive for PVA. Notable regional variations noticed, with Ludhiana showing high incidences of PVYN (78.43%), PVYO/C (31.37%), PVM (33.3%) and PVS (35.29%). Conversely, Kapurthala displayed a 100% PVX incidence, while Jalandhar had the highest PLRV (19.05%) incidence. In nucleic acid-based detection through RT-PCR, the primer NIb2F/3R effectively amplified the desired ~350bp amplicon in all PVYN and PVYO/C seropositive samples. Whereas, the qPVY NIb F2/CP R2 primer generated the ~1.5kb fragment in only 24 out of 67 samples, further confirmed via BLASTn sequence analysis as PVYO, PVYNTN and PVYN-Wi strains. Further virus translocation studies revealed a wide range of carryover rates, spanning from 40% to 92.46%, from infected mother plants to daughter tubers, exhibiting significant variation in viral titre across genotypes and among tubers. Spatial translocation within the tuber's root zone revealed that the bottommost tuber displayed a relatively lower PVY titre. Interestingly, freshly harvested tubers exhibited a higher viral titre at the heel end (stem end) compared to the rose end eyes in all examined tubers. After storage, a contrasting trend emerged in sprouted tubers, where the highest PVY titre was found in rose end eyes and the lowest in heel end eyes. In germplasm screening against resistance to PVY, one germplasm (KP -16-19-14) displayed high resistance (HR), while 16 exhibited resistant (R), 20 moderately resistant (MR), 22 moderately susceptible (MS), 10 susceptible (S) and two were highly susceptible (HS) to PVY. Following PVY inoculation, significant reduction was observed in chlorophyll fluorescence parameters, viz., Fv/Fm, Y(II), qP, and qL values in susceptible cultivars, accompanied by notable increases in NPQ, Y(NO) and qN values. Susceptible genotypes displayed yield losses ranging from 13.64 to 58.84% with viral titre ranging from 0.014 mc to 419.673 mc. Finally, a farmer-friendly and cost-effective vertical flow assay (VFA) was developed for rapid PVY detection in potato leaf samples. The sensitivity of the developed assay was equivalent to commercially utilized ELISA. Specificity test confirmed assays precision for prevalent PVY strains and its non-specificity to other potato viruses. Developed assay exhibited 95% accuracy compared to RT-PCR.
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    ThesisItemOpen Access
    Diversity and management of aflatoxin producing Aspergillus spp. in groundnut
    (Punjab Agricultural University, Ludhiana, 2019) Belludi, Rakesh; Sandhu, P.S.
    Survey was conducted in the major groundnut growing states of India to collect the groundnut samples to detect the aflatoxin contamination. Out of 53 samples collected, 32 isolates were isolated, among them six were of Aspergillus niger, which were proved to be nontoxic by ammonia vapour test. Other 26 isolates were carried for further identifications. Through this study, all 26 isolates were proved to be of A. flavus. Based on the morphological quantitative characters like growth rate, size of the conidia and conidiophores, all the isolates were classified into five clusters by multivariate cluster analysis at 93.13 per cent similarity level. Further, all the isolates were assessed with the qualitative tests to detect the toxigenic strains. In bioassay eight isolates were proved toxigenic and isolate afl 26 from Telangana was the most toxigenic. From ammonia vapour test, it was proved that 14 isolates were toxigenic, among these afl 26 isolate from Telangana was again proved highly toxic. All the isolates which proved toxic were further carried to quantify the aflatoxin production through HPLC. According to this, nine out of 17 isolates were proved to produce aflatoxin B2 above detectable levels, which were above the safe limits of Indian and USFDA standards. The field experiments were conducted to evaluate the effects of cultural practices viz., date of sowing, soil amendments like FYM & lime and bioagents like Trichoderma harzianum & Pseudomonas fluorescens on aflatoxin production. It showed that early sowing of crop in April month reduces the collar rot infection, but it aggravates the aflatoxin producing fungi. Application of FYM and lime reduces the aflatoxin contamination and meanwhile increased the pod yield of the groundnut. Whereas bioagents also reduced the aflatoxin contamination. In another experiment to evaluate the effect of storage conditions on aflatoxin production, higher aflatoxin contamination was found in the pods (inoculated with toxigenic strain afl 26) stored at 35°C with >20 per cent moisture content, hence it is recommended to store the pods at 15°C with 12-15 per cent moisture content.