PhD Thesis

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    Genetic diversity analysis for nutrient efficiency and identification of nutrient responsive genes in cassava (Manihot esculenta Crantz)
    (Department of Plant Breeding and Genetics, College of Agriculture,Vellayani, 2023) Swathy Sivan; Arya, K
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    Diversity interrelationships among capsicum spp. and forms and developement of papricas
    (Department of Olericulture, College of Horticulture, Vellanikkara, 1994) Indira, P; Peter, K V
    Capsicum, a new world genus, has richness in diversity that has not yet received the needed attention. The cultivated chilli varieties offer many problems in classification because of their great number, the transitory nature and creation of new ones through hybridization and selection processes. The present studies on “Diversity inter relationships among Capsicum spp. And forms and development of paprikas” were conducted at the College of Horticulture, Vellanikkara. The main objectives were grouping of chilli genotypes biometrically and biochemically and development of paprikas. For biometrical grouping chilli genotypes belonging to four cultivated species of Capsicum were evaluated during two seasons (August, 1991- January, 1992 and May, 1992- September, 1992). They were clustered into different groups based on D2 values. There were 9 clusters during first season and 6 clusters during second season. The distribution of genotypes into clusters showed no regularity. The isozyme patterns of two enzymes viz.peroidase and esterase were studied in the three cultivated species of Capsicum and also for the nine biometrical groups. Among the different plant parts studied roots showed clear bands in case of peroxidase and mature leaves were the best sampling tissue for esterase enzyme. There were species specific bands in all the three species. The nine biometrical groups showed variation for banding pattern in case of peroxidase and esterase. There were some common bands for both the enzymes. Twenty paprika genotypes were collected from different sources and their morphological descriptions were made as per IBPGR descriptor. Field evaluation was done for two seasons (October –March, 1991; May – October, 1992). There was significant difference among genotypes for the different characters studied. There was much seasonal variation also. CA 517 recorded minimum incidence of bacterial wilt during both seasons under the field conditions. CA 582 showed highest colour value but CA 604 and CA 605 recorded minimum pungency.
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    Diversity analysis in landraces of rice(oryza sativa L.) in Wayanad through morphological and molecular polymorphism study
    (Department of Plant Breeding and Genetics,College of Horticulture, Vellanikkara, Thrissur, 2018) Manjunatha, G A; Elsy, C R
    The present investigation entitled “Diversity analysis in landraces of rice (Oryza sativa L.) in Wayanad through morphological and molecular polymorphism study” was conducted at the Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, Thrissur and Regional Agricultural Research Station, Ambalavayal, Wayanad during the period 2015- 2018. The study aimed to collect and characterize the rice landraces of Wayanad at morphological level and also to characterize the popular aromatic genotypes of the area at molecular level. DUS characterization revealed that, all the landraces under the study exhibited presence of leaf collar, absence of anthocyanin colouration of leaf collar, presence of leaf ligule, split shape of leaf ligule, absence of anthocyanin colouration for plant parts like lemma (keel), area below apex of lemma, stem nodes and presence of secondary branching in panicle. Variability was exhibited for majority of characters namely coleoptile colour, basal leaf sheath colour, intensity of green colour of leaf, anthocyanin colouration of plant parts like leaf, leaf sheath, auricles, ligules, lemma apex, area below apex of lemma, distribution of anthocyanin colouration in leaf, pubescence of leaf blade surface, leaf auricles, culm attitude, density of pubescence of lemma, colour of stigma, attitude of flag leaf blade, curvature of main axis of panicle, lemma and palea colour, presence and colour of awns, distribution of awns in panicle, secondary branching in panicle, attitude of branches in panicle, panicle exsertion, leaf senescence, sterile lemma colour, shape, colour and aroma of decorticated grain, gelatinization temperature and lodging nature.Thavalakannan, Mullan puncha and Sugandhamathi exhibited distinct morphological characters. Among the 60 landraces, Kanni kayama, Ambalavayal-1, Kothandan, Onamottan, Thondi-2, Chenthadi, Kannali and Thondi-1 exhibited significantly high grain yield per plant, which was on par with that of Uma and Aathira (high yielding check varieties), indicating the possibility of commercial cultivation of these cultivars. High PCV value than GCV for all the characters under study, indicated the influences of environmental factors on the characters. High heritability and high genetic gain was exhibited by the characters like length of leaf blade, width of leaf blade, stem thickness, stem length, number of tillers per plant, number of panicles per plant, length of panicle main axis, number of spikelets per panicle, number of grains per panicle, seed setting (per cent), 1000 grain weight, grain length, grain L/B ratio, decorticated grain L/B ratio and grain yield per plant, indicating that these characters could be used in crop improvement programmes. Character association studies including correlation and path-analysis revealed that, five characters viz., width of leaf blade, stem length, number of panicles per plant, weight of 1000 grains and decorticated grain width showed both positive correlation and positive direct effect on grain yield per plant. Cluster analysis based on qualitative characters categorized 60 landraces into 11 clusters at 74 percent similarity level. Based on D2 statistics analysis, the landraces were grouped into seven clusters with variable number of landraces in each cluster, indicating wide genetic diversity in the Wayanad landraces. All the inter-cluster distances were higher than the intra-cluster distance, indicating the wider genetic diversity among landraces of different clusters. Molecular characterization of aromatic rice genotypes of Wayanad by SSR (RM) profiling revealed high level of genetic polymorphism among the genotypes studied. Out of 86 SSR markers used for molecular characterization, 44 markers were polymorphic and remaining 42 were monomorphic. Maximum number of amplicons was exhibited by RM247 with five amplicons, followed by RM85, RM251, RM248 and RM493 with four amplicons each. The highest PIC value was exhibited by RM247 (0.90), followed by RM85, RM251 and RM493 with 0.88 PIC value each. Out of 86 SSR (RM) markers, 21 markers distinguished Basmati from traditional aromatic landraces of Wayanad viz., Gandhakasala and Jeerakasala. Seven SSR markers distinguished Gandhakasala from Jeerakasala, whereas 23 markers distinguished Basmati from Jeerakasala. Twenty-two markers distinguished Basmati from Gandhakasala and 23 markers distinguished aromatic group from non-aromatic group. Cluster analysis for molecular characterization revealed maximum similarity coefficient (1.00) within all the Jeerakasala morphotypes and all the Gandhakasala morphotypes. Cluster analysis effectively differentiated Basmati, Jeerakasala, Gandhakasala, Uma and Aathira from each other. Among the five clusters formed, cluster III was the largest one comprising all the 12 Gandhakasala morphotypes, followed by cluster IV with all Jeerakasala morphotypes. Cluster I, Cluster II and Cluster V exhibited one genotype each namely Aathira, Uma and Basmati, indicating their genetic distinctness.
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    Genetic diversity and combining ability in cucumber (Cucumis sativus L.)
    (Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2017) Suma, A; Elsy, C R
    Assessment of genetic diversity is the key tool in any crop improvement and germplasm management programme. Evaluation of genetic variation will help to provide valuable information about new sources of genes. The studies on combining ability and heterosis can support utilization of promising lines in further crop improvement programmes. Cucumber (Cucumis sativus L. 2n= 2x= 14) is an indigenous vegetable crop of India. Even though rich diversity for cucumber is available in India, studies on genetic diversity of this crop are scanty. Therefore, the present project was proposed to explore genetic diversity in cucumber using morphological and molecular markers and to study combining ability and heterosis in selected genotypes. Morphological characterization of 50 accessions of cucumber revealed presence of significant difference among accessions for majority of vegetative, floral and fruit characters. Mean days to first male and female flower opening was 36 and 43 days respectively. Majority of the accessions possessed elliptical elongated fruits with light green skin colour and white flesh colour. Sixteen accessions exhibited significantly higher fruit length than AAUC-2, the standard check, the maximum being exhibited by IC613472 (20.85 cm). Accessions with oblong ellipsoid fruits possessed higher fruit diameter. Mean fruit weight showed high variability among accessions with a range of 33 g to 343 g. Fourteen accessions exhibited significantly high yield than AAUC-2. Number of fruits per plant, yield per plant, loss of weight during storage and sex ratio showed high values for all the genetic parameters studied. IC613481 was the promising genotype identified in morphological characterization, followed by IC613480. Cluster analysis grouped accessions into seven distinct clusters based on the level of similarity in quantitative characters. Random grouping of accessions into various clusters indicated absence of parallelism between genetic diversity and geographical diversity. Cluster II and III were the largest clusters, with 14 accessions each and Cluster V and VI, the smallest ones with single accession each. Results of Principal component analysis revealed that first three principal components, with Eigen values more than unity accounted for 85.80 per cent of cumulative variance, contributed by fruit weight, fruit length, fruit diameter and days to first harvest. The diversity analysis of the accessions was done using DIVA-GIS by generating grid maps. The results of the study indicated that highly diverse accessions with respect to the selected characters were sourced from Mizoram, Tripura and West Bengal. Molecular characterization revealed high level of genetic distinctness between genotypes. SSR11742 and AF202378 were found to be highly polymorphic markers, with high polymorphism information content and number of polymorphic bands. In-depth evaluation of selected 22 genotypes revealed significant difference for all fruit characters except days to last harvest and harvest duration and further revealed the superiority of IC613480. Evaluation of 15 hybrid combinations developed through half diallel mating design and their parents indicated presence of significant difference among parents and hybrids for various characters studied. Among the parental genotypes, IC613480, exhibited significantly high GCA effects for fruit length, number of fruits per plant and yield per plant whereas IC595508A, for fruit weight and loss of weight during storage, and IC613485 for fruit diameter, thus proving to be promising parents for accumulating genes for these characters. The hybrids, IC613480 x IC595508A and IC613480 x IC613471 showed significant SCA effects for yield per plant and sex ratio. IC613480 x IC613471, IC613480 x IC595508A and IC613471 x IC595508A were exhibiting significantly high relative heterosis, heterobeltiosis and standard heterosis for number of fruits per plant and yield per plant. IC613480 and IC613485 were the most promising genotypes identified from the study whereas IC613480 x IC613471 was the most promising hybrid based on SCA effects, heterosis, per se performance on yield contributing characters and organoleptic qualities. This hybrid showed high fruit length (17.01 cm), yield per plant (2163.45 g), number of fruits per plant (11.43) and sex ratio (0.11). IC613480 x IC613476 and IC613485 x IC595508A were the other promising hybrids.