M H Rashid
Senior Scientific Officer
Oilseed Research Centre, BARI, Gazipur-1701
A K M Aminul Islam
Assistant Professore
Genetics and Plant Breeding Department, BSMRAU, Gazipur
Genetic divergence among 23 genotypes from India, Burma, Bangladesh was estimated using Mahalanobi´s D2 and Rao´s canonical analysis. All together five clusters were formed. The pattern of distribution of genotypes from different geographical location into five clusters was random demonstrating that geographical isolation may not be the only factor causing genetic diversity. Number of bulb per kg onion, leaves length, phosphorus content contributes predominantly towards genetic divergence. Cluster III recorded the highest cluster means for number of leaves per plant, leaves length, bulb diameter, individual bulb weight, dry matter content and for bulb yield. The result obtains from D2 analysis confirmed by canonical analysis.
Onion, Genetic Diversity, Variability
Variety and Species
Information on genetic divergence among plant materials is vital to a plant breeder for an efficient choice of parents for hybridization. It is an establish fact that genetically diverse parents are likely to contribute desirable segregates and/or to produce high heterotic cross. In Bangladesh context the information on this aspect of onion is not sufficient. This study would be very important in breeding varieties for Bangladesh agricultural condition. Therefore, the present investigation was under taken to estimate the nature and magnitude of genetic diversity of onion genotypes.
Seedlings of thirty genotype of onion were raised in 3m×1m-unit bed of thirty seedbeds. Seedlings of 49 days were transplanted in main field in a randomized block design with three replications at experimental field of Bangabandhu Sheikh Mujibur Rahman Agricultural University during rabi season 2006-2007. Each genotype was grown in 10 rows of two-meter length with a spacing of 20cm×8cm. The observation were recorded on 10 competitive randomly selected plants from each plot for nine characters namely number of leaf per plant, leaves length, bulb diameter, individual bulb weight, number of bulb per kg onion, dry matter content, nitrogen content phosphorus content and bulb yield. Plot means over the replications were used for the statistical analysis. Genetic diversity was studied following Mahalanobis (1936) generalised distance (D2) extended by Rao (1952). Canonical analysis was also done according to Rao (1964) to confirm the results of cluster and D2 analysis. Statistical analyses were carried using MSTATC program.
Published paper
The analysis of variance showed significant differences among the 30 genotypes of onion at 1% level indicating the presence of notable genetic variability among the genotype and therefore diversity analysis was carried out.
No parallel relationship was found between genetic and geographic divergence, which may be due to continuous exchange of germplasm from one place to another. Differently originated genotypes found in same cluster or genotypes from same origin were dispersed in different clusters. It was observed that group IV and I formed with eight genotypes originated in India, Burma and Bangladesh and group V occupied by three genotypes but all of were Bangladesh origin. There are supportive reports made by Mohanty and Prusti (2002), Mohanty (2001) in winter onion, Mohanty (1999) in kharif onion.
Genotypes from India, Burma and Bangladesh being in different clusters, indicate the broad genetic variability among the genotypes. There was evidence from Shanmugam and Rangasamy (1982) that materials from same origin distributed in different clusters is an indication of broad genetic base of the genotypes belonging to that origin.
Journal