Fertility variation and gene diversity in seed crops of Eucalyptus and
Casuarina seedling seed orchards in southern India
11234 Kamalakannan, R, Varghese, M, Chezhian, P, Ghosh, M. & Lindgren, D
1. ITC R&D Centre, Spark Tower, SP Biotech Park, Shameerpt, Hyderabad 500 078, India
2. Tamilnadu News Print and Papers Ltd, Kagithapuram, Karur 639 136, India
3. Institute of Forest Genetics and Tree Breeding, P.B. No. 1061, Coimbatore 641002, India email@example.com
4. Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE 901 83, Umeå, Sweden
Four seedling seed orchards each of Eucalyptus (two each of E. camaldulensis and E.
tereticornis) and Casuarina (two each of C. equisetifolia and C. junghuhniana) located at
climatically different sites in southern India were evaluated at four years for fertility variation and its impact on the seed crop. Diversity of the seed orchard crops was compared with that of natural provenances and local land race seedlots using DNA (Inter simple sequence repeat) markers.
The frequency of flowering trees was low in the Eucalyptus orchards (less than 30%) except in one orchard which had 73% flowering trees. The sibling coefficient (;) in the
orchards varied from 2.2 to 17.4 and the corresponding relative effective population size, Nr, varied from 0.45 to 0.06. Casuarina orchards on the other hand had high fertility with more than 80% fertile trees except in one C. junghuhniana orchard which had only 45%
flowering trees. Fertility variation in Casuarina was higher in the inland location (;=5.8
& 7.6) compared to the coastal site (;=2.7 & 2.9). Nr values ranged from 0.17 to 0.36.
Analysis of molecular variation in the Eucalyptus seed lots revealed that 65% of the variance was between seedlots and 35% occurred within the seedlots. In Casuarina seed crops it was 54 % and 46% between and within the seedlots. Cluster analysis and principal component analysis revealed 3 major groups in each genus with the orchard seedlots of each species clustering separately from the natural and local land race seedlots.
The percentage polymorphic loci in the Eucalyptus seed orchard crops was higher (26.1 to 30.7%) than for a bulk seedlot of natural E. camaldulensis provenances (17.9 %). In
Casuarina, the % polymorphism in the orchard seedlots varied from 8.3 to 29.9%. The local land race had comparatively lower molecular diversity than the orchard seedlots in both genera. Remarkable genetic differentiation and low levels of gene flow was detected in native provenances due to geographic isolation. In contrast there was low genetic differentiation between the seed orchard crops. The natural provenance seedlots
of both genera clustered independently, which supports the need for adequate isolation
distance for breeding orchards.
Key words: Casuarina, Eucalyptus, Seed orchard, Fertility variation, Genetic diversity.