Kumar, RajeshRajput, Pushpendra2024-08-222024-08-222023-02Theses of Ph.Dhttps://krishikosh.egranth.ac.in/handle/1/5810213588The investigation entitled ‘Studies on genetic diversity and combining ability in guava (Psidium guajava L.)’ was conducted at Horticulture Research Center, Patharchatta of Govind Ballabh Pant University of Agriculture and Technology, Pantnagar, Uttarakhand during 2019 and 2020. The major objectives of the study were to estimate the extent of genetic diversity, variability, correlation, manifestation of heterosis, general and specific combining ability effects. The experiment was laid down in randomized block design with three replications., 26 guava genotypes were evaluated for morphological characters on the basis of UPOV descriptor and 20 crosses were evolved in line × tester mating design with five lines and four testers. The analysis of variance revealed highly statistically significant difference in all attributes that were observed among tested genotypes. Among components of genetic variability of genotypes, high heritability was obtained for fruit weight (99.71 and 99.77 %) and genetic advance as percentage of mean in flesh core diameter (59.43 and 59.34 %) was estimated during rainy as well winter season crops. Genetic divergence through D2 analysis revealed that during rainy season maximum intercluster distance between clusters VII and V (222.86) and during winter in cluster IX and VIII (197.09) exhibited maximum divergence. The results of F1 hybrids represent that highest genotypic and phenotypic coefficient of variation were recorded in leaf area (15.88 and 17.19 %) and leaf number (15.46 and 15.91 %), respectively. The high magnitude of heritability coupled with genetic advance as per cent of mean was observed for leaf numbers (94.46 and 30.96 %). Parents KG-1 Guava among lines and Local Germplasm among testers have good GCA effect for all characters except that ratio of leaf blade length to width. Crosses KG-1 Guava × Local Germplasm, Hisar Surkha × L-49, KG-1 Guava × Lalit, Hisar Surkha × Pant Prabhat, Sangareddy × Pant Prabhat and Hisar Safeda × Local Germplasm were noted to be consistently good specific combiner for most of the traits. In the case of both relative and better parent heterosis, the F1 crosses namely KG-1 Guava × Local Germplasm, Hisar Surkha × L-49 and KG-1 Guava × Lalit were the best heterotic combination for the traits plant height, leaf number, number of internode, plant girth, leaf blade length and width, leaf area and SPAD units. The findings of investigation revealed that the parent KG-1 guava and local germplasm (plant height, leaf number, number of internode, plant girth, leaf blade length and width, leaf area, petiole length, internodal length and SPAD units), Lalit (leaf number, number of internodes and ratio of leaf blade length to width) and Hisar Surkha (leaf number and ratio of leaf blade length to width) were promising donor based on the general combining ability. The crosses KG-1 Guava × Local Germplasm, Hisar Surkha × L-49, KG-1 Guava × Lalit, Hisar Surkha × Pant Prabhat showed the maximum SCA effects. Hence, these crosses may be advanced to recover desirable segregants for the improvement of yield and its contributing charactersEnglishThesis