1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)
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Item Genetic improvement in Dendrobium orchids through hybridization and molecular characterization(Department of Plant Breeding and Genetics, College of Agriculture,Vellayani, 2023) Amrutha Unni, M.; Beena ThomasThe present study entitled “Genetic improvement in Dendrobium orchids through hybridization and molecular characterization’ was carried out at Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, during 2018-2022, with an objective to assess the genetic variability in commercially important Dendrobium orchids to develop superior hybrids and confirming hybridity through molecular markers. Twenty Dendrobium orchid genotypes with desirable traits and widespread market acceptance were collected, planted in the greenhouse and assessed for variability, heritability, genetic advance and correlation. Analysis of variance showed significant differences among the genotypes for all the characters studied. For the majority of the analysed traits, the mean performance has a broad range of variation among the parents. D. Thong Dang Yellow showed higher mean performance for internode length and plant height. Of the 20 genotypes, 15 flowered, while five genotypes failed to flower due to environmental factors and less adaptations. So the floral characters of 15 genotypes were studied. D. White represented desirable mean values for inflorescence diameter and inflorescence number per plant, D. Rabit Gold showed higher mean performance for pollen fertility and days to first flower opening from inflorescence, D. Gift by God Candy showed higher mean value for flower width in front view and days to last flower opening from first flower and D. Burana Pearl x D. Burana White showed higher peduncle length and vase life. For the vegetative characters, the thickness of leaf exhibited the highest GCV (66.16%) and PCV (69.54 %). High heritability coupled with high genetic advance was recorded for plant height, number of leaves per shoot, number of aerial roots, length of aerial roots, thickness of the shoot, internodal length, length of the leaf and leaf area which indicated that these traits were controlled by additive gene action. For the floral characters the maximum PCV and GCV were found in flower width in front view. All the floral characters showed high heritability along with high genetic advance, demonstrating that these traits were controlled by additive gene action. Plant height showed the strongest positive correlation with the number of aerial roots among the vegetative characters. Significant highly positive correlation was found between the number of inflorescences per plant and the inflorescence axis diameter. Days to first flower opening from inflorescence emergence recorded significant positive correlation with inflorescence axis diameter. Out of the 15 genotypes studied, three genotypes exhibited seasonal flowering nature and all others were free flowering. Inflorescence axis was found to be pendulous in D. Yaya and the rest of the genotypes produced erect or arching type of inflorescence axis. Flower fragrance were present in D. Red Fairy, D. Thong Dang Yellow, D. Popeyes and D. Gift by God Candy. Shape of flower was found as full and round, flat and surfaced with broad sepals and petals. In the study, thirty ISSR primers were used to examine the genetic diversity of 20 orchid hybrid genotypes used in this study. A total of 102 bands were produced, out of which 57 bands found were polymorphic and 45 bands were monomorphic in nature. Polymorphic information content value of the primer ranged between 0- 0.49. Dendrogram was generated using NTSYS-pc 2.02e software and the twenty genotypes were grouped into five clusters. Divergent lines identified were D. Pink bfc, D. Pearl Red Lip and D. King Dragon. The best ten parental genotypes were crossed based on flower synchronization and availability of pollen. A total of 20 cross combinations were attempted. Incompatibility reactions were noticed at different stages ranging from flower abscission before the onset of any visible post pollination change to instances where seeds germinated but aborted in culture. Mature green capsules were harvested from 12 combinations at 70 to 90 per cent maturity. The 12 combinations were inoculated in vitro, but four of them did not produce any seeds in the capsule and one did not germinate. All seven in vitro cultured combinations were successfully germinated and were sub cultured three to four times. The basal media used for the in vitro propagation was half MS. The in vitro growth of the hybrid Dendrobium was improved by supplementing with BA (1 mg/l), IAA (0.1 mg/1) and charcoal (4g/l) was found to be effective. Deflasked seedlings with three or more leaves and three or more roots were then transferred in half MS media. There was significant variance among the number of days required for germination, protocorm development, emergence of first leaf, the first shoot, the first root primordia and deflasking. At deflasking, there were noticeable variations in seedling morphology among the seven hybrid combinations. The present research work identified 10 commercially popular hybrid genotypes that excelled in floral features and diversity attributes. The hybrid plantlets developed through hybridization are to be hardened and maintained in net house for evaluation of morphological and floral traits. These can be utilized in further crop improvement programmes in Dendrobium.Item Investigations on cytogenetics , flowering and seedset in ginger(Department of Plantation Crops and Spices, College of Horticulture, Vellanikkara, 1988) Sathiabhama, K U; Sreekandan Nair, GInvestigation on cytogenetics, flowering and seedset in ginger was carried out at the Department of Plantation Crops and Spices, College of Horticulture, Vellanikkara with the following objectives. 1. To workout the karyomorphology of ginger varieties and to study the cytogenetical polymorphism in relation to the plant morphology. 2. To study the meiotic irregularities in relation to pollen sterility in different varieties. 3. To study the effect of media and irradiation on the pollen germination and pollen tube growth in different varieties. 4. To work out the pollen – pistil interaction by fluorescence microscopy to decide on the presence of incompatibility mechanism in ginger. 5. To study the factor responsible for absence of fruitset and seedset in ginger. The study was carried on nine ginger varieties representing different geographical regions in India. Both morphological and cytogenetical characters were recorded. Studies were also conducted on pollen morphology, pollen-pistil interaction and on methods to over come the barriers in seed set. Absence of morphological difference between varieties adds to the use of cytogenetical investigations for the characterisation of varieties of ginger. The miotic index was found to be maximum during 5-6 AM. All the nine ginger varieties studied showed a chromosome number of 2n = 22. The karyotype of nine varieties of ginger studied showed considerable difference in their morphological features such as length of chromosomes, centromere position, total chromatin length and total chromosome volume. Such differences could have occurred through translocation, inversion and deletion of chromosome segments. Classification of karyotypes in ginger varieties fell in to primitive 1a and 1b group. During meiotic studies it was seen that the genome of ginger is highly unstable. Abnormalities like bridges and laggards were also present which will lead to the formation of micronuclei. Ginger flowers carry enough pollen grains in the single bilobed anther. But 60-84 per cent of the pollen grains were sterile. The high amount of meiotic irregularities may be leading to high percentage of pollen sterility. Out of the seven different media tried for pollen germination, the medium containing 8% sucrose + 60 ppm boric acid + 1% gelatin produced the highest percentage of germination of pollen grains (11.81%). The sterility and pollen germination was also correlated. Irradiation of pollan grains has been suggested to be effective in breaking the barriers in seedset. But it was seen that the irradiation of pollen grains was deteremental for the germination of pollen grains in ginger. Proper interaction between pollen and pistil is quite significant for the seed production. The study by using uv microscopy revealed the presence of spiny stigmatic surface which will prevent proper adherence, contact and germination of pollen grains. It is hard to see whether self and cross incompatibility is operating in ginger. In the present investigation many techniques for breaking incompatibility (if existing) such as bud pollination, artificial sibbing, artificial cross pollination between varieties, chemically aided pollination, mixed pollination, mentor pollination, stigma removal and artificial pollination failed to produce fruitset and seedset. Hence, based on the result the existence of incompatibility mechanism operating in ginger is quite complicated. Structural chromosomal aberrations such as translocation, deletions, inversions etc. leads to the sterility of microspores and megaspores. Pollen sterility ranging from 60 – 84 per cent might be one of the serious limitation for the setting of fruit and seeds in ginger. The spines present on the stigmatic surface prevent the pollen grain to get attached to the stigmatic surface during the act of pollination. Sterility is correlated with pollen germination and it is only upto 14.61 per cent in variety having maximum fertility. The germination of pollen grains was taking place very slowly so that flowers are withered before the pollen tube could reach the ovules. Coiling of pollen tube was also noticed during the advanced stages of pollen germination. The style length was very long (39,000 µ m) in ginger. But the pollen tube attained only 108 µ m in the best case under in vitro condition after 24 hours. So the possibility of pollan tube reaching the ovule is remote by the time flower will be withered and dehisced. The flowers were found to remain on the plant for less than 12 hours after anthesis. In essence, the absence of fruit set and seed set in ginger dose not seem to be controlled by a single factor, but an array of factors make this challenging problem more complex.Item Genetic analysis of yield and quality in fodder cowpea (Vigna unguiculata (L.) Walp)(Department of Plant Breeding & Genetics, College of Agriculture,Vellayani, 2019) Praveena, V S; Mareen AbrahamIn the present study, "genetic analysis of yield and quality in fodder cowpea {Vigna unguiculata (L.) Walp)", evaluation of different fodder cowpea accessions were done to assess the variability in the available population to identify the good performers for forage yield and quality. Based on the morphological and molecular characterization superior parents were selected for crop improvement through hybridization to develop superior cross combinations. The salient features of the study are discussed below. Significant variation was observed for all tlie fourteen characters studied, the range of mean values observed refers to the phenotypic and genotypic variability present in the base population. High genotypic and phenotypic coefficient of variation was observed for number of primary branches plant ', number of leaves plant ', leaf area index, green fodder yield plant ', dry matter yield plant"', leaf fresh weight plant"', stem fresh weight plant"', leaf dry weight plant"', stem dry weight plant"' and crude fiber content. High heritability and genetic advance for crude fiber content, crude protein content, leaf area index, leaf dry weight plant ', dry matter yield plant"', stem dry weight plant"', number of leaves plant"', stem dry weight plant'', number of leaves plant"', stem fresh weight plant"', leaf fresh weight plant*' and green fodder yield plant"'. Green fodder yield and dry matter yield had significant positive phenotypic and genotypic correlation with leaf fresh weight plant"', followed by stem fresh weight plant"', stem dry weight plant"', dry matter yield plant"', leaf dry matter plant"', number of primary branches plant"' and number of leaves plant"'. The thirty fodder cowpea genotypes were grouped into eleven clusters. Maximum contribution to divergence was shown by leaf fresh weight plant"' followed by crude fibre content, stem dry weight plant"', leaf area index, dry matter yield plant*', number of leaves plant"', crude protein content and green fodder yield plant"'. Selection index was hi^est for IT-37154999-38 and least for IC- 202804. The genotypes were ranked for characters green fodder yield, crude protein content, crude fibre content and selection index. Based on this and maximum inter cluster distance eight genotypes CO-8, MFC-09-1, IC-1061, IC- 39916, IC-97767, lC-38956-1, 17-37154999-38 and Pant Lobia-2 were selected for further hybridization programmes. Molecular characterization revealed two clusters (I and II) with 0.34 per cent similarity. The statistical cluster diagram from value and dendrogram from molecular characterization were not similar. But the eight parents selected had considerable difference in dendrogram with minimum difference between parents IT-38956-1 and IT-37154999-38. Diallel analysis is one of the techniques used to find the genetic makeup. Gca variance was greater than sea variance, for all characters except for days to first flowering and crude protein content, indicating predominance of additive gene action for most of the characters. Days to first flowering and crude protein content had non-additive gene action. Presence of heterosis also shows the ability of the parents to combine well in a hybridization programme. Superior expression of Fi may be due to fixable (additive) type of gene action and non-additive type of gene action. Thus combining ability and heterosis helps in identifying desirable cross combinations. Twenty eight hybrids from eight parent were evaluated for combining ability in diallel mating design without reciprocals. Relative heterosis and heterobeltiosis were calculated for different traits. Gca variance was greater than sea variance, indicating predominance of additive gene action. P4, Ps and Pe were good general combiners among eight parents for plant height. Gca variance was greater than sea variance, indicating predominance of additive gene action in green fodder yield and dry matter jdeld. Ps, Pe, P? and Ps were good general combiners for green foddra* yield, dry matter yield, leaf fresh weight, stem fresh weight, crude protein content and crude fibre content. Nineteen of the hybrids were good specific combiners for I7f7^^ ni green fodder yield. Seventeen hybrids were good specific combiners for lower crude fibre content. Pi X ??, P2X P7, P5X P7 and P5X Pg were selected based on high green fodder yield, dry matter yield, higb protein content and low fibre content for raising F2 population. F2 families of these four hybrids exhibited differences among the progenies for different characters studied. Progenies of hybrid PiX P7 was identified as the best superior cross combinant useful for further improvement for superior variety development.Item Introgression of mosaic resistance in popular short duration cassava varieties of Kerala through marker assisted selection(Deparment of Plant Breeding and Genetics, College of Agriculture, Vellayani, 2018) Darshan, S; Arya, KThe present study entitled “Introgression of mosaic disease resistance in to popular short duration cassava varieties of Kerala through marker assisted breeding”was conducted in the Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, Kerala Agricultural University and Division of Crop Improvement, ICAR- Central Tuber Crops research Institute, Sreekariyam, Thiruvananthapuram, Kerala during the period 2014 - 2017 with the core objective of introgression of cassava mosaic disease (CMD) resistance to short duration varieties of cassava through marker assisted selection (MAS) and to study the inheritance of early bulking nature. The research work was carried out as four experiments. In the first experiment, Five early bulking high yielding lines viz, Sree Jaya, Sree Vijaya, Vellayani Hraswa, CI 889 and 9S 75 and three testers viz, CR 54A3, IMS2-5 and CI 273 with resistance to cassava mosaic disease were selected and planted in a pollination block and crossed in Line x Tester (LxT) design to produce hybrid seeds of 15 F1 combinations. Experiment II was conducted in two parts. Screening of F1 seedlings for CMD resistance and early bulking nature was carried out in the first part of experiment II, where hybrids along with the parents were evaluated. Analysis of variance revealed significant differences among the genotypes for all the traits studied. All the agronomic traits were recorded and inheritance of early bulking and its correlation with other traits were studied. The CMD incidence expressed significant and negative correlation with tuber yield per plant where as significant and positive correlation for all other traits with tuber yield per plant was observed among the F1’s. As a part of experiment II (b), seedlings without the CMD visual symptoms were subjected to multiplex PCR and the results revealed that among the parents Sree Jaya, Sree Vijaya, Vellayani Hraswa expressed presence of Srilankan Cassava mosaic Virus (SLCMV) and Vellayani Hraswa expressed the presence of both SLCMV and Indian Cassava mosaic Virus (ICMV). Among the crosses, Sree Jaya x CR54 A3 (L1x T1), Sree Jaya x IMS2-5 (L1xT2), Vellayani Hraswa x IMS2-5 (L3xT2), CI 889 x CI 273 (L4xT3) expressed the presence of SLCMV. Real time PCR (qPCR) assay for seedlings identified CI 889 (L4), 9S 75(L5), CR 54A3 (T1), IMS2-5 (T2) and CI 273(T3) among the parents and Sree Jaya x CR54 A3 (L1x T1), Sree Jaya x IMS2-5 (L1xT2), Sree Jaya x CI 273(L1x T3) and 9S 75 x CR54 A3 (L5x T1), 9S 75 x IMS2-5 (L5xT2) and 9S 75 x CI 273 (L5x T3) among the crosses as highly resistant, based on viral load present in the DNA sample. Based on the previous report ten CMD resistance linked markers were screened through BSA and five of which SSRY 28, SSRY 44 SSRY 40, SSRY 106 and SSRY 235 were selected. Among the CMD linked SSR markers studied, the maximum polymorphism was elucidated by SSRY 28, SSRY 44 and followed by SSRY 235. SSRY 28 is a strongly linked marker to CMD2 which is a dominant gene conferring resistance among the clones of combinations (L1xT1, L2xT2, L3xT1 and L3xT3) three of five markers revealed alleles associated with CMD2 gene In the third experiment to evaluate the early bulking clones, field was laid out in randomized block design (RBD) with three replications consisting of CMD resistant clones along with parental clones using miniset technique. Analysis of variance revealed significant differences among the genotypes for all the traits. Measurement of heterosis was carried out considering parent Vellayani Hraswa (L3) as check and results revealed that standard heterosis was positive and significant in the combinations Sree Jaya x CR 54A3 (L1xT1) and Sree Jaya x CI 273 (L1xT3) for all the yield contributing traits. The crosses Sree Jaya x CR54 A3 (L1x T1) and Sree Jaya x CI 273 (L1xT3) exhibited negative standard heterosis for CMD. Combining ability analysis showed significant gca, sca variances and gca, sca effects for all the traits. Moreover gca/sca variance ratio indicated preponderance of dominance / non-additive gene action for the inheritance of all traits. Among the lines, Sree Jaya (L1) exhibited positive and significant gcaeffect for tuber yield and yield contributing traits. Among the testers, IMS2-5 (T2) exhibited negative and significant gca effect for CMD. Among the crosses Sree Jaya x CR54 A3 (L1x T1) exhibited positive and significant scaeffect for girth of tuber and stem girth, 9S 75 x CI 273 (L5xT3) exhibited positive and significant scaeffect for tuber yield per plant, CI 889 x CR 54A3 (L4xT1) exhibited negative and significant scaeffect for CMD. In the last experiment, through bulk segregants analysis using 5 SSR markers linked to early bulking in cassava were selected out of 9 SSR markers selected. Among 5 SSR markers of CMD and early bulking nature two SSR markers (SSRY 28 and SSRY 106) associated with resistance to CMD and One SSR marker, ESTs (SSRY) 292 associated to early bulking nature has been identified. Among the crosses, clones from Sree Jaya x CR54 A3 (L1xT1), Sree Jaya x CI 273 (L1x T3) and 9S 75 x CR 54A3 (L5xT1) are being confirmed with CMD resistance as well as early bulking nature.Item Marker assisted backcross breeding for pyramiding genes conferring resistance to bacterial blight in rice variety uma(Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2018) Megha, L M; Rose Mary FranciesAs in other rice growing locales around the world, bacterial blight (BB) caused by Xanthomonas oryzae pv. oryzae (Xoo) assumes a huge role in deciding rice profitability in Kerala. The elite rice varieties of Kerala, both PTB 39 (Jyothi) and Mo 16 (Uma), are found to be extremely susceptible to bacterial blight. Since both the major rice cropping seasons (virippu and mundakan) in the state coincide with monsoons, the control of the disease through chemicals or biological agents proves inadequate owing to the washing-off of the applied materials. Host-plant resistance is advocated as the most effective breeding strategy to combat the bacterial blight (BB) pathogen. Considering the impact of the disease on food security and sustainability, efforts were taken to introgress three R-genes (xa5, xa13 and Xa21) into the variety Uma from donor parent Improved Samba Mahsuri (ISM) through Marker Assisted Selection (MAS). Further, backcrossing to Uma (recurrent parent) and advancing the resultant BC1F1s have resulted in production of BC2F1 generation (21 Nos.). The present study aimed to identify BC2F1 plants pyramided with genes (xa5, xa13 and Xa21) conferring resistance to bacterial blight using functional markers. In addition, advancing the R-gene introgressed BC2F1s to BC3F1 and BC2F2 generation was envisaged. Pathotyping of BC1F2s (850 Nos.) and generating BC1F3s from the plants exhibiting resistance to BB pathogen was also aimed at. Foreground selection of the BC2F1 individuals using the xa5 gene linked STS marker RG 556 and functional marker xa5 SR confirmed the presence of the R-gene in the parents as well as the 21 BC2F1 individuals. Screening of BC2F1 individuals with STS marker RG 136 linked to R-gene xa13 and functional marker xa13 promoter revealed that the BC2F1 Plant No. 8.3.9.10 was heterozygous at xa13 locus while, all other BC2F1 individuals possessed alleles similar to that of the recurrent parent (RP) Uma. The result also pointed out that BC2F1 Plant No. 8.3.9.10 was a 2-R-gene pyramid (xa5xa5 + Xa13xa13). Foreground selection with STS marker pTA 248 to detect the presence of Xa21 gene revealed that none of the BC2F1 plants analysed except BC2F1 Plant No. 8.3.9.10, possessed the resistant allele of R-gene Xa21. However, presence of alleles of both the parents in Plant No. 8.3.9.10 indicated that it was heterozygous at Xa21 locus. Results obtained thus revealed that, of the 21 BC2F1s subjected to foreground selection, BC2F1 Plant No. 8.3.9.10 was the only 3-R-gene introgressed pyramid (xa5xa5 + Xa13xa13 + Xa21xa21). In addition, the 3-R-gene introgressed BC2F1 Plant No. 8.3.9.10 was subjected to background screening using 22 rice microsatellite (RM) markers. Background profiling revealed that the banding pattern in Plant No. 8.3.9.10 was similar to recurrent parent in case of thirteen RM markers. The plant was found to be heterozygous at five other marker loci. Considering the segregation of the 22 markers, the magnitude of recovery of recurrent parent genome in 3-R-gene introgressed BC2F1 Plant No. 8.3.9.10 was found to be 81.82 per cent. The dendrogram based on molecular data grouped the individuals into two major clusters. Cluster 1 was monogenic with only the donor parent ISM and cluster 2 comprised of the recurrent parent Uma and Plant No.8.3.9.10, further suggesting that the 3-R-gene introgressed BC2F1 Plant No. 8.3.9.10 was more similar to the recurrent parent Uma. Wide variability was observed among the BC2F1 individuals for various morphological traits. The 3-R-gene introgressed BC2F1 Plant No. 8.3.9.10 was shorter in duration than both the parents and also possessed red kernels similar to the recurrent parent Uma. The dendrogram generated based on the morphological characters also indicated greater similarity between the 3-R-gene pyramid and recurrent parent Uma. The identified 3-R-gene pyramid (BC2F1 Plant No. 8.3.9.10) was backcrossed to both recurrent parent Uma as well as selfed resulting in production of BC3F1s (15 Nos.) and BC2F2s (28 Nos.) respectively. Bioassay of BC1F2 population (106 Nos.) through leaf clipping method of pathotyping suggested by IRRI (1991) revealed that more than half the BC1F2 individuals screened exhibited resistance to BB pathogen. The plants that exhibited moderate reaction to BB infection ranged between 16.87 per cent and 34.78 per cent in progeny of BC1F2 Plant No. 8.3.2 and BC1F2 Plant No. 8.3.9 respectively. Selfing of the BC1F2 individuals exhibiting resistance and moderate resistance to BB pathogen resulted in production of 725 BC1F3 seeds. Modern molecular techniques make it possible to use markers and probes to track the simultaneous introgression of several R-genes into a single cultivar during a crossing programme. Foreground and background profiling of backcross generations can ensure precise identification of R-gene introgressed genotypes that resemble the recurrent parent Uma.Item Development of functional ssr markers for d-limonene content and analysis of genetic polymorphism in cardamom (elettaria cardamom maton)(Department of Plant Biotechnology College of Agriculture, Vellayani, 2018) Reshma Retnakaran; Sabu, K KItem Characterization of okra [Abelmoschus esculentus L. Moench] genotypes in North Kerala(Department of Plant Breeding and Genetics, College of Agriculture, Padannakkad, 2017) Aswathi G Prasad; Namboodiri Raji VasudevanItem 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 RAssessment 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.Item Metagenomic analysis of bacterial diversity in the rhizosphere of arecanut palms affected by yellowing in Wayanad(Department of Agricultural Microbiology, College of Horticulture, Vellanikkara, 2017) mahesh Mohan; Girija, D