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ThesisItem Restricted Mapping of Phytophthora resistance in intergeneric rootstock population of citrus(Punjab Agricultural University, 2023) Amandeep Kaur; Sidhu, Gurupkar SinghThe investigations entitled “Mapping of Phytophthora resistance in intergeneric rootstock population of citrus” were carried out in 2020-22. In the present study, screening of Phytophthora related traits of 88 F1 hybrids population (pseudo-testcross) of Rough lemon × Swingle citrumelo was done by spore suspension and filter method. Data were recorded after 90 days of inoculation for different symptoms and growth attributes related to Phytophthora. Phenotypic characterization for qualitative and quantitative characters of F1 hybrids were done based on IPGRI descriptor. Hybrids were showed great variation in percentage of unifoliate, bifoliate and trifoliate leaves, spine length, habitus, branch size, shoot tip colour, young leaf colour, adaxial colour, abaxial colour, leaf lamina shape, leaf apex, leaf margin and petiole colour. Based on the studied 14 attributes, 88 F1 rootstock hybrids revealed different degree of response to Phytophthora. Out of 14 traits, feeder root rot rating, chlorotic leaves and gummosis rating scale (0 to 4), 23 plants were highly susceptible, 19 plants susceptible, 6 plants moderately resistant, 12 plant resistant and 28 plants in highly resistant. In vitro filter method, lesion size was used to find the degree of resistance and observed that 20 were highly susceptible, 19 susceptible, 12 moderately resistant, 13 resistant and 24 in highly resistant. For genotyping, 165 SSR markers were used for parental polymorphism. Further, a genetic linkage map of citrus F1 hybrids has been constructed by using 116 polymorphic SSR markers comprising of 9 linkage groups, spanning a distance of 1476.19 cM. From the identified, twenty six major Quantitative trait loci (QTL), two QTLs for feeder root rot rating observed on chromosome 2 at 32.54 cM and 14.26 cM having Left flanking marker HvSSRCM-241. A total of 2 QTLs (qGR.RL.pau-5 and qGR.RL.pau-8) for gummosis rating were detected on LG5 & LG8. The proportion of the total variation (R2) ranged from 10.98 to 14.52%, respectively. Third experiment was conducted for mass multiplication and conservation of potential hybrids through cutting. Different types of cutting viz., soft, medium and hard wood cuttings from unifoliate and multifoliate hybrids in rainy and spring season were treated with 500, 1000, 1500, 2000 ppm IBA along with control. Among the cutting taken, medium wood cutting during rainy season and spring season in unifoliate performed better in all the parameters whereas during spring season hardwood cutting of multifoliate hybrids performed better. IBA concentration @ 1000 ppm followed by 500 ppm was the best concentration for all the parameters. Overall, the unifoliate hybrids RL×SW-19 & RL×SW-29 and multifoliate hybrids RL×SW-6 & RL×SW-7 were performed better for all the parameters. The phenotypic linkage so constructed will pave the path for high resolution mapping of Phytophthora resistance traits with high throughput marker segregation techniques like genotyping by sequencing on citrus genetic map. Cutting propagation will provide new insights for future mass multiplication from the limited material.ThesisItem Restricted Effect of generally recognized as safe (GRAS) chemicals on storage behaviour of pear (Pyrus pyrifolia) cv. Patharnakh(Punjab Agricultural University, Ludhiana, 2018) Amandeep Kaur; Gill, P P SThe present study entitled "Effect of generally recognized as safe (GRAS) chemicals on storage behaviour of pear (Pyrus pyrifolia) cv. Patharnakh" was carried out in the Department of Fruit Science, PAU, Ludhiana during the year 2017. Physiologically mature, uniform fruits were thoroughly washed, disinfected and dipped in aqueous solutions of boric acid (1, 2 and 3%) sodium bicarbonate (1, 2 and 3%) and sodium benzoate (1, 2 and 3%) for five minutes. The fruits were placed in CFB boxes and subsequently stored at (0-1°C and 90-95% RH) for 70 days. The fruits were analyzed after 0, 20, 40, 60 and 70 days of storage. PLW of fruits decreased with storage; however, fruits treated with boric acid @ 3% recorded significantly lower PLW as compared to other treatments. Similarly, fruit firmness, acidity, total phenolics and SOD activity showed declining trend with increase in storage period. Total soluble solids (TSS), cellulase activity and sugars were increased up to 60 days of storage and thereafter, a decline was recorded in all treatments throughout the storage period. Fruit sensory quality rating was increased upto 40 days of storage in all the treatments except control fruits where in sensory quality increased upto 20 days of storage. The TSS/acid ratio, PPO activity and spoilage increased with advancement of storage. The PME acivity was increased upto 60 days of storage in all the treatments except boric acid treated fruits in which PME activity increased upto 70 days of storage. During cold storage, boric acid @ 3% treatment was found most effective in extending the storage life of Patharnakh pear fruits with acceptable quality fruits during the entire storage period.