Abstract

Genetic divergennce was studied for seed yield and six important yield components in Indian mustard ( Brassica juncea Czern & Coss ). Divergence study helped in grouping 55 Indian mustard genotypes into eight diverse clusters. Cluster I comprising of 24 genotypes. whereas clusters VI, VII and VIII comprised of one genotype of each. Clustering of population did not follow their geographic or location distribution. Seed yield per plant showed maximum divergence followed by number of siliqua on main shoot and minimum by number of primary branches per plant. The inter cluster distance was maximum between clusters V and VIII ( 713.86) followed by clusters V and III ( 454.36 ). Therefore, it will be logical to attempt crosses between the genotypes belonging to clusters V ( PBR 181 and PBR 135 ) and VIII ( PBR 154 ) to obtain desirable segregants for the development of high yielding varieties with quality of oil.

Introduction

In the south-western part of Punjab and adjoining area, Indian mustard ( Brassica juncea Czern & Coss ) in an important rabi crop extensively grown as rainfed as well as under irrigated conditions. therefore, it becomes necessary for the plant breeder to develop varieties of Indian mustard, best suited to both the cropping systems. Genetic improvement, in turn, will require information on various parameters of variability. Also improvement on seed yield and quality is normally achieved by selecting the desirable genotypes in the segregating generations following intervarietal hybridization. For the choice of diverse parents for the hybridization programme, multivariate analysis using Mahalanobis’D² - statistic has been extensively used as a quantitative measure of genotypic divergence among the parents. Therefore, an attempt has been made to study genetic divergence among fifty five elite genotypes of Indian mustard.

Material and methods

Fifty five genetically diverse Indian mustard genotypes were grown in randomized block design at PAU, Regional Research Station, Bathinda during rabi 1996-97. Each genotype had two rows of 5.0 m length with row to row and plant to plant spacing 30 cm and 10 cm respectively. the crop was raised with recommended agronomic practices. The data were recorded on five competitive plants for number of primary branches, number of secondary branches, plant height ( cm), main shoot length (cm), number of siliqua on main shoot, oil content (percentage) and seed yield per plant (g). To assess the genetic divergence, data were analyzed using Mahalanobis’s D² -statistic described by Rao ( 1952 ).

Results and discussion

Selection, which is the basis of every breeding programme operates only on variation which is of genetic nature and a wide range of variability present in any crop, always provides the better chances of selecting desirable types. In the present study, analysis of variance for fifty five Indian mustard genotypes showed significant differences for all the characters, indicating the existence of genotypic variability and validated further genetic analysis.

Mahalanobis’s D² -statistic helped in grouping fifty five genotypes of Indian mustard into eight clusters ( Table 1. ). Cluster I comprising of 24 genotypes. Whereas clusters VI, VII and VIII were comprised of one genotypes in each only. Clustering of population did not follow their geographic or location distribution. Similar observations have also been reported by Barua et al., ( 1996); Mahto (1996); Sandhu and Gupta ( 1996) and Krishnapal and Ghose (1992).

Contribution of different characters towards total genetic divergence ( Table 2. ) revealed highest contribution of seed yield per plant ( 19.33 %) followed by number of siliqua on main shoot ( 17.10 % ). The genetic divergence contribution was least by number of primary branches ( 7.67 %). Cluster means of different clusters revealed maximum values for seed yield per plant, number of siliqua on main shoot, oil content ( percentage ), main shoot length, number of primary branches and number of secondary branches in clusters VIII, V, VIII, V, VII and V respectively. The intra and inter-cluster distance among various clusters ( Table 3. ) revealed that lowest intra cluster distance for clusters VI, VII and VIII. The maximum intra-cluster distance was observed in cluster IV ( 138.977). The inter-cluster distance was maximum between clusters V and VIII ( 713.855 ) followed by clusters V and III ( 454.357).

From the above discussion, therefore, it is logical to attempt crosses between the genotypes belonging to clusters V ( PBR 181 and PBR 135) and VIII ( PBR 154 ) to obtain the desirable segregants for the development of high yielding varieties with high quality of oil. Similarly crossing of genotypes belonging to clusters V and III and Clusters V and VII, may also prove useful in this context.

References

1. Barua, P.K.; B. Langthasa and R.K. Choudhary. 1996. Genetic diversity in Indian rapessed ( Brassica campestris L. ). J. Oilseeds Res., 13 (1): 113-115.

2. Krishna, P. and S.K. Ghose. 1992. Heterosis in relation to genetic divergence in rapessed and mustard. J. Oilseeds Res., 9(1): 169-174.

3. Mahto, J.L. 1996. Genetic divergence and stability in Indian mustard under rained conditions. J. Maharashtra Agric. Univ., 21(3): 334-337.

4. Rao, C.R. 1952. Advance Statistical Methods in Biometrical Research. John Wiley and Sons Inc., Newyork.

5. Sandhu, S. K. and V.P. Gupta 1996. Genetic divergence and correlation studies in Brassica species. Crp Improv., 23(2): 253-256.

Table 1. Clustering pattern based on D²-statistic in Indian mustard

Table 2. Clusters means for different characters and percent contribution of different characters to divergence in Indian mustard.

Table 3. Intra and inter-cluster distances (D²) in different characters in Indian mustard