MOR RPHO-GEN NETIC AN NALYSIS AND EX S XPLOITAT TION OF HE ETEROSIS AMONG HIP BE S G EARING H HYBRID R ROSES

Abstract

Roses have contributed to our social, economic and religious life hence they are called “Index of Civilization”. Presently in Pakistan most of the rose cultivars have been introduced from other countries hence they fail to fit in new environmental conditions of the country. Keeping in view the importance of this issue present study was aimed to get insight into the breeding procedure, complexities and tactics leading to achieve hybrid progenies and to study the magnitude of hybrid vigor inherited in the next generation of parent roses. For this purpose, comparatively well acclimatized and hip producing cultivars including “Autumn Sunset”, “Iceberg”, “Paradise”, “Angel Face”, “Casino”, “Louise Odier”, “Grand Margina”, “Handel” and “Gruss an Teplitz” were selected for crossing. They were planted in the Rose field of Institute of Horticultural Sciences, university of Agriculture, Faisalabad, Pakistan. Morphological description of all cultivars revealed various blends of color of flowers, foliage and leaf hairiness, petiole pubescence and inflorescence types. Data regarding flowering and yields traits also varied in all varieties, however over all better performance was exhibited by the cultivars Iceberg and Gruss an Teplitz scoring 2.5 points each. Poor performance was exhibited by the cultivar Louise Odier. The genotypic and phenotypic and environmental coefficients of variations varied for all quantitative traits. Strong positive correlation was exhibited between number of flowers per plant and overall performance of bushes, flower diameter and petal length, bush shape and height of the plant however fragrance was negatively correlated to flower persistence life. Cluster analysis of the parent on the basis of quantitative traits revealed four major clusters which predicted the different performance for some traits but same for other. Within the individual cluster all the cultivars almost behaved similar. Results about pollen vigor parameters indicated that great variations in pollen quality, quantity, and viability and germination % ages. Maximum number of pollens per anther were exhibited by the cultivar Handel (1612.3) followed by cultivar Angel face (1588.7). Minimum numbers of pollens per anther were counted in the cultivar Iceberg. On average basis the performance of Angel face and Handel was better with respect to both number of anther per flower and number of pollens per anther. Pollen size (L: D) was almost same in all cultivars hence no significant differences were observed. Comparison of means of viability %age revealed that maximum number of viable pollens in term of viability %age were possessed by cultivar Handel (70%) followed by ‘Gruss an Teplitz’ (64%). The minimum viability of pollens was exhibited by the Cultivar ‘Autumn Sunset’ having pollen viability of 35%. Germination medium having 15% sucrose proved very effective for optimum germination results as compared to 10% and 20% sucrose. On average basis the cultivar ‘Grand Margina’ yielded maximum pollen tube length of 46.556 μm followed by ‘Gruss an Teplitz’ having pollen germination of 40.333 μm. The minimum pollen tube length of 9.222 μm was observed in cultivar ‘Iceberg’. Cluster analysis of cultivars on the basis of pollen quality and vigor parameters revealed three main groups. A strong correlation among pollen germination %age and pollen tube length (r = 0.77) and pollen germination %age and pollen viability %age (r = 0.731) was exhibited. Pollen germination is also strongly correlated with pollen size (r =0.738) The comparison of various fertility parameters in vitro and in vivo revealed that cultivar “Handel” showing its maximum pollen viability in vitro performed well with respect to giving more crossing success in field as compared to its average pollen germination %age invitro conditions followed by the cultivar Autumn Sunset. Cultivar Ice Iceberg did not yielded any successful cross. Maximum hip setting %age (83) was observed in for the cross combinations Iceberg x Gruss an Teplitz and Iceberg x Casino and minimum (30%) in Louise Odier x Paradise. Number of seed per hip also varied from 33 to 15 in all cross combinations. Response of seeds with respect to germination also varied significantly after treating the seed with various storage temperatures and acid treatments. Results indicated that germination period (F= 89.95, F<0.05), germination %age (F=67.16, P<0.05), imbibition period (F=26.13, P<0.05) and seed vigor index (F= 112.2, P<0.05) was affected significantly by all treatments accordingly. All the treatments also affected morphological traits of seedlings as well. Evaluation of hybrida in the field revealed that all the F1 hybrids produced showed significant variations in qualitative and quantitative traits over their parents. Data regarding heterosis and heterobeltiosis %ages showed also negative and positive results for various traits over their parents. Variations were observed for flower color and diameter, prickles, bush shape and overall performance of all F1 hybrid progenies. Performance of F1 progenies was evaluated in the field conditions while having comparison with their respective parents and data was analyzed by ANOVA to check the significance of variations in the parents and progenies and comparison of means. Further, more hybrid vigor estimation (Heterosis and Heterobeltiosis) proved a useful tool to check the superiority and inferiority of progenies over their parents. Cluster analysis of the parent cultivars and progenies was useful to develop realation on the basis of similarity index among parent and hybrid progenies. Hybrid identification and genetic diversity studies among parents and progenies evaluated by SSR markers also confirmed the contribution of both parents for the development of F1 hybrids. For genetic diversity study SSR loci proved very effective to amplify across parent cultivars, hybrids and to assess their polymorphic contents. Ten of the SSR primers exhibited similar sequence with known gene. Estimates of genetic diversity varied remarkably among loci. Observed heterozygosity (Ho) based on Nei’s estimation revealed that the locus H10, CL9 and RW54 contributed equally for generating more variation and scored maximum number of alleles for respective locus. Allele fixation trends were also observed for different loci and individual groups. Total gene diversity (Ht) was calculated and mean for all loci was 0.852 while the average gene diversity (Hs) for all loci was calculated as 0.768. It was clear from the dendrogram that parent cultivars compiled themselves into four main groups. Little differences were observed within the groups of parent cultivars. Confirmation of hybrids was done by comparing the common alleles between parent and hybrid against all primers. More over phenatic relationship was developed among hybrid progenies and parents to confirm the extent of contribution of each parent for genetic makeup of hybrid. All other hybrids were identified in the same method. It is concluded from the present study that hybrid cultivars have varying level of fertility and it is necessary to evaluated them in search of vigorous pollen donor parent. It is concluded from the result that diallel was not possible as most of the crosses failed. However ANOVA, comparison of means and Cluster analysis aided by SSR fulfilled the objective. Hybrid progenies exhibited vigor over parents for some traits but for other traits they remained uneffective in the climate of Faisalabad city. SSR markers proved helpful tool for confirmation of F1 hybrids and discriminating the parent cultivars and progenies.