Selection of Genetically Divergent Clones of Casuarina equisetifolia for Further Breeding Programmes

Genetic divergence studies were carried out in clones of Casuarina equisetifolia L. selected from Chidambaram/ Chengalpet (CH/CP) and Tiruchendur (TCR) in Tamil Nadu, India. 33 CH/CP clones and 43 TCR clones were subjected to the analysis separately at 8 years of age. Mahalanobis’ D2 technique was used to study the genetic divergence and the clones were grouped into different clusters using the Tocher’s method. Tree height, diameter at breast height, collar diameter, crown length, cladode length, cladode diameter, number of primary branches, frustum volume and volume index were the characters used for the analysis. Application of Mahalanobis’ D2 statistics and Tocher’s clustering method grouped the CH/CP clones into eleven clusters with cluster strength varying from one (clusters X and XI) to eleven (cluster V) and the TCR clones into seven clusters with cluster strength from one in cluster VII to twelve in cluster VI. Among the various characters, volume index contributed the maximum towards genetic divergence. Based on the inter and intra-cluster distances, male clones CH 3004, CH 0401, CP 0207, CP 3903, CH 2604 and CP 1501 and female clones CH 2703, CH 2803, CP 3703, CP 0301 and CH 3002 are recommended for further breeding programmes from the CH/CP group. From the TCR group of clones, TCR 110202, TCR 090201 and TCR 030101 (male) and female clones, TCR 040204, TCR 120102, TCR 080201, TCR 120203 and TCR 090102 are recommended. The results on genetic divergence have got an immediate application in the establishment of clonal seed orchards. Information on genetic distance between genotypes helps in developing planting design, such that it can facilitate equal opportunity for hybridization among the genotypes and obtaining quality seeds with high vigour.