Abstract
The study was carried out to investigate the genetic diversity, heterosis and combining ability in okra during the period from 2003 to 2005 at the Regional Agricultural Research Station, Bangladesh Agricultural Research Institute (BARI), Jamalpur and Bangladesh Agricultural University (BAU), Mymensingh. Evaluation and characterization of 121 okra genotypes were done using 22 quantitative and 16 qualitative characters. Genotypes × environment interaction effects showed significant variation among 121 okra genotypes. Some genotypes performed better at BARI, Jamalpur and some genotypes performed better at BAU, Mymensingh. But 14 genotypes consistently demonstrated better yield at both the locations. Among them AE009, AE024, AE036, AE061, AE080 and AE087 were found promising.
Genetic diversity studies of okra were done using morphological, isozyme and random amplified polymorphic DNA markers. Based on ten morphological characters, 121 okra genotypes were grouped into nine clusters using D² analysis. Days to first flowering, number of fruits per plant, fruit weight and fruit yield per plant positively contributed towards divergence in both the vectors. The highest inter genotypic distance (560.40) was recorded between AE024 and AE028, and the lowest (5.00) was between AE019 and AE032. According to principal coordinate analysis, the highest inter-cluster distance (28.04) was between clusters IX and I, and the lowest (2.26) was between cluster II and VI. Genetic diversity of okra was studied using peroxidase isozyme extracted from young leaves. Uniform resolution and good consistency was found in 9.0% acrylamide gel electrophoresis and produced eight zymotypes of 29 bands at different Rf values ranging from 0.05 to 0.42. Similarity coefficient was found from 0.00 to 42.86%.RAPD analysis of 121 okra genotypes using five random decamer primers generated 38 DNA bands of which 32 (84.21%) was polymorphic with the size from 200-1600 bp. Nei’s gene diversity was 0.18 and Shannon’s information index was 0.29 across all the loci. The highest genetic distance was found 0.693 among the genotypes of okra. Number of internodes per plant, length of fruit, diameter of fruit, number of fruits per plant, fruit weight and number of seeds per fruit had significant positive correlation with fruit yield. Path analysis showed that number of fruits per plant and fruit weight had higher direct effect towards yield in okra.Considering magnitude of genetic divergence, inter and intra-cluster distance, contribution towards divergence and other horticultural attributes, eight parents were selected for hybridization programme, and crosses were done in half diallel fashion. Combining ability analysis indicated that both additive and non-additive gene actions were important in governing the yield and its component characters. On the basis of heterosis and combining ability, the following hybrids viz. AE024×AE036, AE024×AE061, AE024×AE080, AE036×AE080 and AE056×AE080 were selected for further evaluation with the view for developing a hybrid variety of okra.