Dhatt, K. K.Maninderpal Singh2022-02-112022-02-112021Maninderpal Singh (2021). Combining ability analysis for growth and flowering characteristics of periwinkle (Catharanthus roseus L.) (Unpublished Ph.D. Dissertation). Punjab Agricultural University, Ludhiana, Punjab, India.https://krishikosh.egranth.ac.in/handle/1/5810182093The current experiment entitled "Combining ability analysis for growth and flowering characteristics of periwinkle (Catharanthus roseus L.)" was conducted at the Floriculture Research Farm of Punjab Agricultural University, Ludhiana during the years 2018 to 2020. Eight inbred lines of periwinkle viz. P1 (Vi-15-1-3-4), P2 (Vi-24-2-3-5), P3 (Vi-81-3-2-2), P4 (Vi-63-4-6-7), P5 (Vi-15-2-6-5), P6 (Vi-14-3-7-6), P7 (Vi-14-9-6-5) and P8 (Vi-13-2-3-1) were crossed in half diallel fashion (excluding reciprocals) with an objective of identifying the lines with high general and crosses with high specific combining ability, to assess the gene action and to estimate the extent of heterosis for growth and flowering characteristics. The eight parental lines along with their twenty eight F1 hybrids were evaluated in Randomized Block Design having three replications. The observations recorded on plant height, plant spread, number of branches per plant, leaf width, leaf length, petiole length, internodal length, days to flowering, flowering duration, number of flowers per plant, flower diameter, corolla tube length and follicle length revealed highly significant results; indicating the presence of sufficient variability. The results for the analysis of variance for general combining ability (GCA) and specific combining ability (SCA) were also found to be highly significant for different growth and flowering characters which indicated the presence of both additive and non additive gene action. Based on GCA effects, the parents P5 and P8 were regarded as best general combiners for most of the traits and may be used in breeding programme for population improvement in desirable direction. Studies on specific combining ability of the crosses indicated that the cross combinations P12, P15, P17, P18, P25, P28, P35, P38, P45 and P46 were having superior results for most of the characters studied. The variances due to GCA were higher for plant height, leaf width, petiole length, days to flowering and corolla tube length, suggesting the control by additive gene action and selection can be useful in their improvement. While, the estimates of SCA variances were higher for plant spread, number of branches per plant, leaf length, internodal length, flowering duration, number of flowers per plant, flower diameter and follicle length; indicating the presence of non-additive gene action in the expression of these traits and heterosis breeding can be employed for their improvement. Heterosis studies revealed that majority of the hybrids exhibited better and mid-parental heterosis in desired direction for most of the characters studied. The crosses viz. P12, P17, P18, P28, P36, P38, P46 and P78 recorded significant heterobeltiosis for various characters. High to moderate estimates of phenotypic and genotypic coefficients of variation were recorded for majority of the traits studied, reiterating the presence of variability. The PCV showed a range of variation from 5.36% to 30.73%; while the GCV varied from 5.21% to 26.22%. The heritability estimates had a range of 56.08 to 94.57% in the broad sense and all the characters were having high or moderate values, showing that the characters were highly heritable to the next generations. Genetic advance as percent of mean ranged from 10.44 to 46.09 percent. Moderate to high heritability along with high genetic advance was observed for plant height, plant spread, number of branches per plant, petiole length, internodal length, number of flowers per plant, and follicle length which indicated the control by additive gene action and selection can be used. For internodal length, days to flowering and flowering duration the occurrence of moderate heritability along with moderate genetic advance as per cent of mean suggested that these traits were controlled by both additive and non-additive gene actions; while flower diameter and corolla tube length had high heritability along with moderate advance suggesting that these were controlled by non-additive gene action, so these can be improved by using heterosis breeding. The correlation coefficients exhibited positive association of number of flowers per plant with plant height, plant spread, number of branches per plant, flowering duration, and days to flowering; both at phenotypic and genotypic levels. As per the path analysis, the selections based on flowering duration, plant spread and days to flowering will improve the number of flowers per plant significantly through direct and indirect selection. The result of analysis of variance for F2 generation revealed highly significant mean sum of squares for all the vegetative and flowering traits among various genotypes. High to moderate heritability was observed for most of the parameters in F2 generation, while varying from 24.40 to 91.96%. Genetic advance as per cent of mean varied from 3.71 to 25.10%. The estimation of correlation and path analysis revealed that number of flowers per plant was associated with plant height, plant spread, number of branches per plant, flowering duration and days to flowering.EnglishThesis