Genotypic and Phenotypic Characterization of Some Selected and Standard Clones of Tea [Camellia Sinensis (L) O. Kuntze]

Abstract

Present investigation was under taken with a view to study and evaluates the extent of genetic variation present among 12 selected tea genotypes. This study also includes the analyses of major biochemical and nutritional components present in the selected tea genotype. In addition, the extent of genetic diversity was also assessed with RAPD markers among the 12 tea genotypes. The 12 tea genotypes selected for this study were MZ/39, E/4, D/13, B2×T1, Br/2/97, SDL/1, BT2, Ph/9/4, Ph/9/25, Ph/9/40, BS-67 and BT5 collected from the germplasm repository of Bangladesh Tea Research Institute (BTRI). All the field experiments were conducted in the experimental field of BTRI at Srimongal in Moulvibazar district, Bangladesh. The laboratory experiments were conducted in the Plant Breeding and Gene Engineering Laboratory of the Department of Botany, University of Rajshahi. In order to study the extent of variability, 15 quantitative characters viz., angle of the first branch, height, length and breadth of the plucking surface, length, breadth, length and breadth ratio, and leaf angle of the fifth leaf, pluck able shoot length, fresh weight, dry weight and fresh and dry weight ratio of pluck able shoots, leaf area and shoot density of pluck able shoots, and pluck able shoot yield/plant were used as parameters. The data on these characters were statistically analyzed to calculate the variability, coefficients of variability, heritability, genetic advance as % of mean, principal component of variation, correlation coefficient, path coefficient analysis and genetic diversity. The results of this study reveal that the presences of wide range of variations for almost all the quantitative characters were found. In the present study, the highest genotypic component of variation (GCV) was observed for pluck able shoot yield/plant followed by leaf area of the pluck able shoot, leaf angle of the fifth leaf and shoot density. These results suggest that the greater extent of variability in most of the characters was genetic in nature which are less affected by environment and hence could be improved through selection. Heritability estimates in broad sense were relatively high for almost all the characters studied. In the present study high heritability estimates for leaf breadth, leaf angle, leaf length and breadth ratio and the length of the fifth leaf, dry weight, leaf area and fresh weight of pluck able shoots, and angle of the first branch were found associated with high genetic advance as percentage of mean, which suggested that the scope of improvement of these characters through selection. Out of 14 quantitative characters, five yield contributing characters viz., height of the plucking surface, length of the plucking surface, breadth of the plucking surface, angle of the first branch and shoot density selected through Ridge regression were subjected for correlation coefficient and path coefficient analysis. Correlation coefficient analysis showed that the pluck able shoot yield/plant was positively and significantly correlated with height, length, breadth of the plucking surface and shoot density. Path coefficient analysis using genotypic correlation reveals that height and length of plucking surface and shoot density had direct positive influence on leaf yield. These characters also showed significant positive correlation with yield. Therefore, selection on the basis of these characters should get preference for future improvement of pluck able shoot yield. The results of principal component analysis (PCA) reveal that the first two principal components accounted for 46.92% of the total variance. Genetic diversity among the 12 genotypes as determined using multivariate analysis shows that the 12 tea genotypes could be grouped into two different clusters (C1 and C2). The maximum numbers of genotypes were included in Cluster 1. The evaluation of the tea quality through organoleptic test reveals the significant difference in total tea quality tasting score among the 12 genotypes. According to the tasters’ quality score, all genotypes could be categorized as good (above average) quality except Ph/9/40 which was categorized as average. The results on antioxidant activity reveal that the amount of total phenolic compounds was significantly different among the tea genotypes. Among the 12 genotypes, the highest amount of phenolics was found in BT5. The content of phenolics in the leaf extracts correlates with the antioxidant activity. The total antioxidant capacity determined as equivalent to ascorbic acid of the methanolic extract of fresh leaves of 12 tea genotypes were also significantly different among which BT5 performed the highest antioxidant capacity. The DPPH (1,1-diphenyl-2-picrylhydrazyl) assay of free radical scavenging activity of the methanolic extract of leaf compared with butylated hydroxytoluene (BHT) at 519 nm shows that the highest antioxidant activity (IC50 value of 39 μg/ml) in BT5 genotype. The biochemical and nutritional components viz., gallic acid, theobromine, theophylline, caffeine, epigallocatechin, catechin, epicatechin, epigallocatechin gallet, gallocatechin gallet, epicatechin gallet and catechin gallet were analyzed in methanolic leaf extracts of 12 different tea genotypes through HPLC. The results reveal that among the 12 genotypes, Ph/9/25 showed the highest percentage of gallic acid, whereas no gallic acid was found in the genotypes D/13, B2×T1 and BS-67. The tea genotypes MZ/39, E/4, Ph/9/25 and Ph/9/40 showed the highest amount of total alkaloid content (theophylline, theobromine and caffeine). The highest amount caffeine content was recorded in Ph/9/40 followed by MZ/39 and Ph/9/25. The caffeine content was the lowest in BS-67. On the other hand, among all the genotypes, total catechin content was the highest in D/13 followed by E/4 and MZ/39. Randomly amplified polymorphic DNA (RAPD) assay was performed to estimate the genetic diversity among the twelve tea genotypes.The genomic DNA amplified with ten decamer primers (OPA-7, OPA-9, OPA-10, OPB-10, OPB-13, OPC-9, OPC-17, OPD-3, OPD8 and OPD-15) showed total 83 distinct score able bands of which 64 (77.18%) bands were polymorphic. The highest percentage polymorphic loci were found in OPC9 and e the lowest loci (60%) in OPA9. The highest genetic distance was found between the Ph/9/25 and MZ/39 whereas the lowest genetic distance was found in SDL/1 and MZ/39. By The consensus phylogenetic dendogram generated using PAST (PAleontological STatistics) programme based on genetic distances segregated the twelve tea genotype into three different groups as clusters. Genotype E/4, D/13, MZ/39 and SDL/1 formed group A cluster, genotype B2×T1, BT2 and BT5 made group B cluster and Br2/97, Ph/9/4 and genotype Ph/9/40 grouped in C cluster. The result indicates the genetic diversity among the tea genotypes and RAPD marker could be used for improvement of tea cultivars.