Fertility Variation and its Implications on Relatedness in Seed Crops in Seedling Seed Orchards of Eucalyptus camaldulensis and E. tereticornis

Abstract

Seedling seed orchards of Eucalyptus tereticornis (N = 192 & 505) and E. camaldulensis (N = 182 & 525) were established at two sites (one moist and one dry) in southern India. The fertility (based on the number of flowers and fruits) was registered for each tree at age eight and nine years. E. camaldulensis on the moist location had 73 % fertile trees and low fertility difference (sibling coefficient, Ψ, was 2.27) at eight years. whereas Only 23 % trees were fertile in the E. tereticornis orchard at the same site and the fertility variation was high (Ψ =11.71). In the dry location, fertility was almost the same in both species at nine years, with 45 & 51% fertile trees in E. camaldulensis (Ψ = 5.4) and E. tereticornis (Ψ = 5.2) respectively. Though the fertility trends were the same in both years, the number of fertile trees was comparatively higher at nine years (except in the low flowering E. tereticornis orchard at the moist site) in both the sites. Gene diversity values of the seed crop estimated for two consecutive years are fairly high except for the E. tereticornis (GD = 0.9650 and 0.9690) orchard located in the moist site. The implications of fertility variation on diversity of progeny have been discussed in the light of domestication strategies and tree breeding programs implemented for eucalypts.

Changes in growth performance and fecundity of Eucalyptus camaldulensis and E. tereticornis during domestication in southern India

“…When assembling seed collections from superior trees for advanced generation breeding, the relatively low levels of flowering observed in this study and in the same orchards at later age of 8-9 years (Kamalakannan et al 2007) would have substantially reduced the genetic diversity passed on to the progeny. Large orchards, retaining more trees and located at sites conducive to heavy flowering, would be required to ensure capture of most of the newly introduced alleles in open-pollinated breeding populations (Zobel et al 1988).…”

“…At age 8 years, SPAs 1 and 3 (E. camaldulensis and E. tereticornis at the drier site) had 26% and 28% of trees flowering, respectively-only a modest increase over 4 years (Kamalakannan et al 2007). Nine years after planting, the percentages of trees flowering at these two SPAs had increased to 45% and 51%.…”

Impact of fertility variation on genetic diversity and phenotypic traits in second generation seed production areas and clonal seed orchards of Eucalyptus camaldulensis

“…Sibling coefficient (Ψ) was calculated from the number of genotypes in the stand (N) and individual fertility (ρ 1 ) of each tree to describe fertility variation among the trees (Kang et al, 2001), Group coancestry (Θ) is the probability that two genes taken at random from the gene pool of the expected seed crop will be identical by descent. Since the current plantations originated from parent orchards established from a wide base of more than 500 trees of 11 native provenances (Kamalakannan et al, 2007) and several unrelated clones the trees in SPAs and CSOs were considered to be non-related and non-inbred. All pairwise coancestries will thus be equal to zero and all self-coancestries equal to 0.5 and the Θ can be calculated (Kang and Lindgren, 1999) as where ρ 1 is the probability that genes sampled at random from the gamete pool originate from genotypes i.…”

“…A breeding program for E. camaldulensis was implemented in southern India with seed collections from over 500 selected trees of 11native Australian provenances (Doran et al, 1996). Improved seed was supplied to farmers from first generation unpedigreed and pedigreed seedling seed orchards (Kamalakannan et al, 2007;Krishnakumar et al, 2014). Many of these plantations have been used to produce seeds to meet the large planting stock requirement of farm forestry.…”

“…Fecundity of orchard trees can be used to predict gene diversity of seed crop and relatedness among progeny, by estimating fertility variation and co-ancestry (Lindgren and Mullin, 1998). Fertility based gene diversity estimates have been used to determine overall benefit from seed orchards (Kang et al, 2001;Kamalakannan et al, 2007), while molecular markers have been widely used to evaluate genetic structure and diversity of seed orchards (Chezhian et al, 2010;Jones et al, 2006). The correlation between predicted gene diversity, and genetic diversity estimated from molecular markers is not well evaluated.…”