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2012 - 201922020 - 20231
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Author: Amandeep Kaur × Start date: 1968 × Thesis Type: Ph.D ×
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    Mapping of Phytophthora resistance in intergeneric rootstock population of citrus
    (Punjab Agricultural University, 2023) Amandeep Kaur; Sidhu, Gurupkar Singh
    The 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.
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    Allele mining for phospholipase D locus to improve the rice bran quality
    (Punjab Agricultural University, Ludhiana, 2016) Amandeep Kaur; Kuldeep Singh
    Rice (Oryza sativa L.) is the most important staple food for a large part of the world’s population. Rice bran which is a by-product after milling is rich in oil (12–23%), proteins (14–16%), vitamins and crude fiber (8–10%). Rice bran oil is typically an oleic–linoleic type fatty acid and qualifies for good quality edible oil. The primary limitation of rice bran as a source of oil is the presence of highly active lipolytic enzyme Phospholipase D alpha1 (PLDα1) that increases free fatty acids content in the oil and causes the ‘stale flavor’ in the product. The wild relatives of rice constitute a major gene pool for rice improvement. In this study, sequence based allele mining of the gene PLDα1 (6.28 kb) was taken up in wild species of rice to identify potentially novel alleles for bran quality improvement. Differences in expression patterns were also investigated for potential correlation with sequence variation. A representative subset of 86 accessions belonging to 16 wild Oryza species and eight O. sativa cultivars were selected for this purpose. Alignment of the assembled sequence contigs relative to the Nipponbare reference (Os01g0172400) gene revealed the presence of 2555 variations (SNPs and InDels). Highest polymorhism at PLDα1 locus have been detected in the O.officinalis species. Expression profiles in immature grains generated by exon-specific qRT-PCR indicate significant differences in transcript abundance within as well as between the selected accessions and different 3’and 5’ truncated PLDα1 mRNA. Cis-elements identified in the upstream sequences showed variations relative to the reference in low expressing wild species accessions. These results suggest that potential PLDα1 allelic variants are defined by differential regulation at the levels of transcription initiation and/or mRNA splicing. The wild species accessions with variations in protein structures and low expression, identified in the present study, can be further utilized in the breeding programs to transfer desirable allele into elite lines through marker assisted selection.
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    Physiological basis of nitrogen use efficiency in maize (zea maysl.) at various rates of applied nitrogen
    (PAU, 2012) Amandeep Kaur; Bedi, Seema
    Field and laboratory experiments were conducted at Punjab Agricultural University, Ludhiana during kharifseason in the years 2009 and 2010 respectively to study the physiological basis of nitrogen use efficiency in maize (Zea mays L.) at various rates of applied nitrogen. Six maize genotypes (hybrids and their parents) i.e., long duration PMH1 (parents LM13, LM14) and short duration JH3459 (parents CM143, CM144) were raised under five nitrogen levels viz; recommended (RDN), RDN+25%, RDN+50%, RDN-25% and RDN-50% respectively. Various ecophysiological traits viz; leaf area, leaf area index (LAI), fraction of PAR intercepted by plants (FRI), intercepted photosynthetically active radiation (IPAR), radiation use efficiency (RUE) were significantly improved with the application of nitrogen at higher than the recommended rates in both long and short duration genotypes. Low nitrogen levels increased anthesissilking interval and shortened the duration of grain filling. It also caused a reduction in grain yield and its determinants mainly harvest index, 100-kernel weight, cob weight, above ground biomass, shelling percentage, cob length and diameter, number of kernel rows per cob and number of kernels per cob. The various physiological traits such as plant height, crop growth rate, relative growth rate, dry matter accumulation, root-shoot ratio etc. were significantly increased with the application of 25% and 50% higher nitrogen than the recommended. The applied nitrogendose also affected the content of various biochemical constituents (total soluble sugars, total soluble proteins, total starch content, chlorophyll content as well as the activity of various enzymes viz., nitrate reductase (NR), glutamine synthetase (GS), glutamate synthase (GOGAT) and PEP carboxylase). Path coefficient analysis showed that various traits such as RUE, LAI, FRI, IPAR, GS and NR activity had the maximum positivedirect contribution to grain yield in both set of maize genotypes (long and short duration). Therefore, these traits should be used as target traits to improve maize grain yield at both high and low nitrogen levels. The various quality parameters (starch, proteinand oil) in grains of both long and short duration genotypes were maximum in the treatment RDN+50%. Aminoacid content (total free amino-acids, tryptophan and methionine content) was significantly decreased with the decrease in nitrogen (RDN-25%; RDN-50%) than the recommended. In contrast, there was a decreasing pattern in nitrogen use efficiency (NUE), nitrogen remobilization efficiency (NRE) and nitrogen harvest index (NHI) values with increasing fertilizer rates in both long and short duration genotypes. Hybrids i.e. PMH 1 (long duration) and JH 3459 (short duration) were more responsive to variations in nitrogen supply than their female and male parents. Moreover, the high nitrogen use efficiency for hybrids (PMH1, JH3459) as compared to their parents (LM13, LM14 ; CM143, CM144) was associated with greater PAR interception during the growth period , high radiation use efficiency (RUE), more harvest index (HI), high photosynthetic capacity associated with increased acitivity of PEP carboxylase enzyme and high chlorophyll content in leaves, high nitrogen metabolic efficiency, increased activity of nitrogen metabolism enzymes (nitrate reductase, glutamine synthetase and glutamate synthase) leading to higher nitrogen harvest in dex. Keywords:GOGAT, GS, maize, nitrogen, NR, NUE, PAR, PEP carboxylase, RUE, yield