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Epidemiology and Management of Post harvest diseases of Kinnow mandarin
(Punjab Agricultural University, Ludhiana, 2021) Gurwinder Kaur; Raheja, Sandeep
Surveys were conducted periodically (twice in a month) from January to March during 2019 and 2020 to record the incidence and prevalence of major post-harvest rots of Kinnow mandarin and pathogens associated with it in South-western Punjab. Highest incidence of post-harvest rot of Kinnow mandarin 20.21 and 12.59 percent was observed in the month of March during the year 2019 and 2020, respectively. Penicillium digitatum and Penicillium italicum causing green and blue mould rots were found to be two most prevalent post-harvest pathogens with their prevalence of 30.88 and 26.44 percent, respectively during 2019 and 32.44 and 24.88 percent, respectively, during 2020. Temperature of 25˚C favoured maximum radial growth (84.67 mm) of both test pathogens also, maximum percent disease index of green (95.00 percent) and blue mould rot (90.00 percent) was recorded at 25˚C. The pH 5.5 and 6.0 supported maximum radial growth of P. italicum by 90.00 & 88.66 mm and of P. digitatum by 88.67 & 87.67 mm, respectively and were found to be at par with each other. Among different GRAS chemicals and botanicals evaluated against test pathogens, copper sulphate, boric acid, sodium bicarbonate and sodium carbonate at 100mM and above concentrations among chemicals and garlic extract at 10 per cent and above concentration among botanicals showed complete inhibition (100.0 percent) of both test pathogens under in vitro, whereas, under in vivo garlic extract at the concentration of 15 percent showed complete inhibition of green (100.0 percent) and of blue mold rot (92.22 percent). Boric acid at the concentration of 4 percent showed complete inhibition (100.0 percent) of both the test pathogens.
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Characterization of blast and bacterial blight resistance genes in basmati rice
(Punjab Agricultural University, 2022) Vashisth, Tanvi; Jain, Jyoti
The present study was conducted to evaluate MCF1 populations of basmati rice developed from complex crosses (designated as cross A and cross B). Phenotypic evaluation of cross A was done for resistance to neck blast (Pyricularia oryzae) using highly virulent isolate NB-7 under artificial inoculation conditions. Cross B was evaluated against neck blast (NB-7) as well as bacterial blight (Xanthomonas oryzae pv. oryzae) using two pathotypes PbXo-7 and PbXo-8 under artificial inoculation conditions. Among the MCF1 population comprising of 421 plants from cross A, 12 plants were immune, 6 were highly resistant, 30 were resistant and 59 were moderately resistant to neck blast isolate NB-7. A population of 103 plants from cross B showed immune response to neck blast in 9 plants, while 12 plants were resistant to pathotype PbXo-7 and 27 plants were resistant to PbXo-8. Both the crosses were also analyzed for known blast resistance genes (Pi54, Pi2, Pi9 and Pi68) and bacterial blight resistance genes (xa13 and Xa21). A total of 200 plants were tested in cross A, and 199 were found to have the Pi54 gene, while 155 had the Pi2 gene. Only 4 plants showed the presence of Pi9 gene in cross A. The combination of two blast resistance genes was found in 149 plants (Pi54 + Pi2) and in four plants there was a combination of three genes (Pi2 + Pi54 + Pi9). In the cross B, only two plants showed the presence of blast resistance gene (Pi9) and 40 plants showed the presence of Xa4 gene. Two plants were heterozygous for bacterial blight resistance gene (xa13) and four were heterozygous for Xa21. There were only two plants identified as having blast + BB resistance genes (Pi9+Xa4) and one plant showing two BB resistance genes (Xa21+Xa4). The assay of biochemical parameters indicated a significant increase in activity of peroxidase, PPO, PAL, catalase and hydrogen peroxide among resistant/moderately resistant genotypes as compared to the susceptible genotypes at 10 days after inoculation with P. oryzae. Out of 35 genotypes screened against leaf and neck blast phases under artificial inoculation conditions, none was found to be resistant to both the phases. Only two entries viz., Tetep and Pusa Basmati 1637 showed moderately resistant reaction to both neck and leaf blast with susceptibility index (Sx) value <3. Three genotype namely JJ92, UPR3519-18-1-1 and IET 15392 exhibited moderately resistant reaction to leaf blast but were moderately susceptible to neck blast under artificial inoculation conditions. Under natural epiphytotic conditions (hotspot location), five entries namely JJ92, UPR3519-18-1-1, IET 15392, Tetep and Pusa Basmati 1637 showed moderately resistant reaction to neck blast and resistant reaction to leaf blast. The current study has the potential to contribute towards strengthening ongoing blast and bacterial blight resistance breeding program by utilizing the identified donors harbouring single as well as multiple resistance genes to both the diseases.
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Factors affecting aggressiveness of Sclerotinia sclerotiorum (Lib.) de Bary inciting stem rot of rapeseedmustard
(Punjab Agricultural University, Ludhiana, 2022) Chetan V. N.; Sandhu, P S
The stem rot caused by Sclerotinia sclerotiorum (Lib.) de Bary is one of the major diseases of rapeseed-mustard. In this study, factors affecting aggressiveness of the pathogen were evaluated using isolates collected from various rapeseed-mustard growing regions of India. These isolates were estimated for development of the disease, oxalic acid production, total cellulase and cutinase activity. These isolates were significantly different w.r.t. their aggressiveness which highly correlated with oxalic acid production and cutinase activity and moderately with total cellulase activity. Low and high aggressive isolates were sequenced to detect variation in genes Sscut and Ssoah1. No variation was seen in Sscut while Ssoah1 showed 7 synonymous SNPs. Further study was conducted to test the efficacy of alkali salts such as sodium carbonate (SC), potassium silicate (PS), sodium propionate (SP) and calcium propionate (CP) against Sclerotinia stem rot. Under in vitro conditions, the PDA media amended with SC (0.6-1 per cent), PS (0.8-1.2 per cent), CP and SP (1.6-1.8 per cent) showed complete mycelial growth inhibition when compared with un-amended PDA medium. In case of detached leaf assay, SC @ 1 per cent, PS @ 1.4 per cent, SP @ 1.8 per cent and CP @1.8 per cent were effective in inhibiting lesion development of pathogen when compared to untreated leaves. Effective treatments were tested under field conditions at two locationswhere different treatments were sprayed with different alkali salts 2 days before the inoculation. The pooled data of both the locations revealed that CP @ 1.8 per cent showed highest percent reduction in mean lesion length (63.35 per cent) followed by SP @1.8 per cent with 57.77 per cent reduction. The yield data showed negative correlation with lesion length which implies significant reduction in yield of control as compared to treatments.
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Web blight of mungbean (Vigna radiata L.) and its management
(Punjab Agricultural University, Ludhiana, 2022) Raghveer Singh; Sharma, Krishan Kumar
Web blight of mungbean, caused by Rhizoctonia solani, has a significant impact on grain yield and quality. The pathogen is soil-borne and has a broad host range. Field surveys were conducted in different districts of Punjab during the year 2019-20. The survey concluded that Ludhiana district had the lowest prevalence and severity of web blight, while Ballowal Saunkhri (SBS Nagar) had the most. Pathogen variability was investigated at morphological and molecular level. On the basis of morphological characterization viz. colour, mycelial abundance, shape and size of sclerotia, the pathogen was identified as Rhizoctonia solani. Of all the five isolates, BS (Ballowal Saunkhri) and NS (Nawanshahr) were found to be the fast-growing isolates with a 0.88 mm/hr growth rate followed by RO(Ropar) and L1(Ludhiana 1) and L2 (Ludhiana) 0.68 mm/hr. Among all the isolates, L1-L2, BS-L1, RO-L1, NS-L1, and NS-BS were vegetatively compatible, whereas BS-L2, NS-L2, BS-RO, RO-NS, RO-L2 were vegetatively incompatible. The isolates were characterized on the basis of ITS region sequence homology and confirmed as R. solani. The sequences have been registered with NCBI as accession numbers ON17668, ON176686, ON084814, ON084815 and ON084816. Further, Among the three inoculation techniques viz. soil inoculation, foliar spray and field screening at hotspot location, the foliar spray technique was found to be the most precise inoculation technique. Among the four biocontrol agents viz. recommended consortium (LSMR 1+RB3), a new consortium (Bacillus subtilis +RB1), Trichoderma viride, and Pseudomonas flourescens, the new consortium (Bacillus subtilis +RB1) was found most effective against web blight under both in vitro and in vivo conditions. Further, a set of 58 elite mungbean genotypes was screened for web blight resistance by field screening technique at hotspot location. Out of 58 genotypes, seven namely, SML 2061, SML 2056, SML 2064, SML 2055, SML 2073, SML 2065 and SML 2070 showed resistant reaction to web blight.
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Population structure and mating type distribution of Ascochyta rabiei from Northern India
(Punjab Agricultural University, Ludhiana, 2022) Lovepreet Singh; Amarjit Singh
A set of twenty-four isolates of Ascochyta rabiei causing Ascochyta blight (AB) of chickpea were collected from different chickpea growing areas of Northern India. The AB isolates were assessed for their virulence pattern on a set of varieties with varying levels of resistance viz; PBG 5, PBG 7, PBG 8 and L 555. Disease severity was observed as the lowest in case of AB 19 i.e. 2.83, indicating that it was the least virulent isolate on all four varieties. Likewise; the most virulent isolate was observed as AB 1 which showed the highest disease severity i.e. 7.9 on 1-9 rating scale. On the basis of virulence pattern, all the isolates were clustered into two main groups – Group A (14 isolates) and Group B (10 isolates). The mean disease severity of group A ranged from 4.75 to 7.83 whereas in case of group B, the disease severity ranged from 2.83 to 5.17. Genotyping of all 24 AB isolates with 27 SSR loci produced 119 alleles ranging from 2 to 8 in number and 138 to 490 bp in size with an average of 5.42 alleles per marker. The observed heterozygosity was zero in all the populations. This may be due to absence of sexual spores in India and presence of only haploid pycnidiospores of this fungus. Further, the percent variation between the populations was very small i.e. 0.56%. However, the genetic variation within the population was very high i.e. 99.93%. The unweighted neighbour-joining dendrogram grouped the 24 isolates of the three populations into three major clusters. Cluster I included isolates 1 and 6, cluster II consisted of 11 isolates 20, 4, 11, 24, 9, 14, 8, 21, 13, 15 and 18. Cluster III consisted of 11 isolates 2, 5, 12, 23, 3, 19, 7, 16, 17, 10 and 22. Principal coordinated analysis (PCoA) showed that overall, the AB isolates were grouped into four major groups. Clumpak (barplot) clustering of individuals into populations based on multi-locus genotyping grouped the isolates into 3 clusters with an admixture indicating no clear-cut geographical origin-based sub structuring of the population. The MAT1-2 primer amplified in all the isolates giving an amplicon of ~ 800bp whereas MAT1-1 did not amplify in any of the isolates. It indicated that only one mating type ie; MAT1-2 was present in all the AB isolates. For confirmatory study the 800 bp amplicon produced by MAT1-2 primer was sequenced and subjected to BLAST analysis which showed 81.05 to 98.29% homology with Didymella rabiei strain ATCC 76501MAT 1-2-1 (MAT 1-2-1) gene.
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Characterization of Karnal bunt (Tilletia indica) resistant genotypes and disease dynamics under alternate cultivation practices of wheat
(Punjab Agricultural University, Ludhiana, 2022) Jaspreet Kaur; Vineet Kumar
A set of 1305 genotypes was evaluated against Tilletia indica under artificial epiphytotic conditions during cropping seasons of 2020-21 and 2021-22. After screening for two years, 284 lines were found to be highly resistant reaction and 289 lines showed resistant reaction (0-5% KB infection). Out of 284 highly resistant lines, diversity analysis of 173 Triticum aestivum lines using 70 SSR markers concluded that majority of the lines were different from each other and have potential to be explored for identification of KB resistance loci. The effect of seed and soil borne inoculum under four different tillage methods viz. happy seeder, super seeder, zero tillage and conventional (control) was studied. Super seeder (infected seed in infected soil) showed highest teliospore count (22,580 per 250 g of soil) and lowest count (1602 per 250 g of soil) was observed with zero tillage (healthy seed in healthy soil). There was significant effect of tillage methods on teliospore count. However, no significant difference of sowing dates was observed on teliospore count. The effect of seed and soil borne inoculum on germination revealed that maximum (80.66%) germination percentage was observed when healthy seed were sown in healthy soil using super seeder while minimum germination (52.26%) was observed with infected seed sown in infected soil using happy seeder. The study needs to be undertaken further to confirm the results obtained in the present investigation.
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Management of Sclerotinia stem rot of rapeseed mustard using plant defense inducers
(Punjab Agricultural University, Ludhiana, 2021) Sudam, Shelke Saraswati; Sandhu, P.S.
The stem rot caused by Sclerotinia sclerotiorum (Lib.) de Bary is one of the major diseases of rapeseed-mustard. In this study, plant defense inducers salicylic acid and sodium propionate, fungicide azoxystrobin, carbendazim and bio-control agents Trichoderma harzianum and Pseudomonas fluorescens were evaluated for the management of Sclerotinia stem rot of rapeseed-mustard. These treatments were given as seed cum foliar treatment and foliar sprays alone. In field trials conducted during 2019 and 2020, the highest per cent reduction in mean lesion length was in carbendazim @0.2 per cent as seed treatment cum foliar spray, which was 56.76 and 80.81 per cent during 2019 and 2020, respectively. It was followed by application of 100 ppm azoxystrobin as seed treatment cum foliar spray that gave 35.14 and 64.18 per cent reduction during 2019 and 2020, respectively. Under in vitro conditions carbendazim completely inhibited the growth of the pathogen at all tested concentrations followed by 150 ppm salicylic acid which inhibited growth by 49.44 per cent. The bio-control agent T. harzianum showed antagonistic activity against S. sclerotiorum and restricted growth by 45.19 per cent. The biochemical studies showed that application of 150 ppm salicylic acid as seed cum foliar spray resulted in increased activity of POD which was 217.61 units/ min/ gfw and SOD activity which was 60.09 units/ min/ gfw at 72 hours after inoculation. The PAL enzyme activity was found to be highest at 120 hours after inoculation which was 765.05 µg-t-cinnamic acid formed/ hour/ gfw. The lignin content and total phenol content was increased at 168 hours after inoculation which was 24.40 mg/g and 1.82 mg/g respectively. In quantitative expression analysis, the significant increase in activity of BjPAL and POD genes was observed at 72 hours after inoculation when compared with control. This suggests that seed treatment and foliar application of plant defense inducers are effective for induction of defense responses against S. sclerotiorum in rapeseed-mustard.
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Understanding virulence spectrum of Rhizoctonia solani under rice-potato cropping system
(Punjab Agricultural University, Ludhiana, 2021) Thakur, Ajaysingh; Lore, Jagjeet Singh
Sheath blight of rice, caused by Rhizoctonia solani is significantly reduces grain yield and quality of rice. The pathogen is a soil borne having wide host range which infect potato causing black scurf. Field surveys were conducted in different districts of Punjab during year 2019-20. The survey revealed that severity of rice sheath blight found maximum in Ludhiana and minimum in Hoshiarpur district. The main aim of the study was to find out the cross infectivity of the pathogen and to study the variations occurring in the pathogen with respect to morphological, pathological and molecular aspects. Fifty Rhizoctonia isolates showed large variation with respect to morphological and cultural characteristics which were grouped into seven major clusters. For pathological characterization, all Rhizoctonia isolates were inoculated on rice genotypes viz Tetep, J-85, D-256, D-6766, PR-108, PR-126 and Te-Qing and potato varieties namely Kufri Pukhraj and Kufri Jyoti. Five different groups were identified based on virulence pattern such as avirulent, least virulent, moderately virulent, virulent and highly virulent. Two isolates P-1 and P-2 belonged to group A were avirulent on rice genotype. Group E consisted of twelve isolates which showed highly virulent with disease severity of 53.9 to 70.0 per cent. Tetep showed the lower disease severity of 38.5 per cent. Molecular characterization of Rhizoctonia isolates was done using species specific markers, AG subgroup specific markers and ISSR primers. Out of three Rhizoctonia species (R. solani, R. oryzae-sativae and R. oryzae), R. solani was found dominant in Punjab state. The Rhizoctonia isolates collected from rice sheath blight, belonged to AG1-IA and two isolates from potato were classified as AG3-PT. Genetic diversity of Rhizoctonia isolates using ISSR primers found higher degree of PIC value ranging from 0.69 to 0.90. On the basis of genetic diversity and marker index, primer R25 considered as highly informative and R19 as least informative marker. On the basis of morphology and virulence, re isolates from potato showed greater variation with original rice isolates. The genetic structure of Rhizoctonia isolates and species in mixed infection is being thoroughly investigated for better understanding of pathogen adaption to facilitate in the disease resistant breeding program.
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Yellow mosaic disease resistance in Vigna species and potential green bridges for legumoviruses in Punjab
(Punjab Agricultural University, Ludhiana, 2021) Rohan Kumar; Sirari, Asmita
Yellow Mosaic Disease (YMD) is reported to be the most destructive viral disease on mungbean caused by Yellow mosaic Virus belonging to genus Begomovirus of the family Geminiviridae. Development of YMD resistance in cultivated mungbean varieties remained unsuccessful due to highly variable nature of pathogen. In present study, 12 wild accession of mungbean and various weeds were collected. In different wild accession level of resistance were analysed in natural field condition and in artificial condition, samples were subjected to specific primers of LYMV (MYMV/MYMIV) out of 12 wild accession 4 accession were showing HR (high resistance) Vigna umbellata (GP1), V. radiata var satulosa (GP11) V. sublobata (GP2) and V. sublobata (GP12). All accessions showed presence of whitefly but count on HR accession (Vigna umbellata (GP1)(11.66), V. radiata var satulosa (GP11)(9.33), V. sublobata (GP2)(10.00) and V. sublobata (GP12)(12.13)) was less than susceptible check(SML 1082)(23.66). 36 weeds were collected from different locations of Punjab and were subjected to RCA and out of 36 samples 9 samples were amplified specific band size 2.8kb afterward these sample subjected to LYMV specific primer (MYMV/MYMIV). All 9 samples showed presence of MYMIV virus but MYMV virus was not present in any sample. Then to know the presence other virus in these 9 samples. Keeping this in view, in present study, the degenerate primers PALIc1960 and PARIv72 were used to amplify the RCA enriched DNA of weeds. All nine weeds showed association of Begomoviruses, confirmed with amplicon of ~1.2bp. Further, these amplicons were sequenced for characterization of Begomoviruses harbouring in weeds during off season by outsourcing from Agri Genome Pvt. Ltd. The nucleotide-BLAST results of sequences revealed the presence of Tomato leaf curl Palampur virus in Baru (Sorghum halepense), Ivy gourd, (Coccinia grandis), Leh, (Cirsium arvense), Button weed, (Malva parviflora), Jangli halon (Coronopus didymus), Maina (Medicago polymorpha) and Tik weed (Tridax procubens), while Billygoat weed (Ageratum conyzoides) and Sadabahar (Catharanthus roseus) showed presence of Ageratum enation virus and Papaya leaf curl virus respectively.

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