Craig Hardner

THE RELATIONSHIP BETWEEN CROSS SUCCESS AND SPATIAL PROXIMITY OF EUCALYPTUS GLOBULUS SSP. GLOBULUS PARENTS

The genetic structure of Eucalyptus globulus forest was examined using progeny vigor as an indirect measure of parental relatedness. Seven trees were crossed with pollen from trees: 0 m (seifing); 21 m (nearest flowering neighbors), 250 m, 500 m, 1 km, 10 km, and 100 km away from the female. Only selfing depressed seed set. Growth of the 21 m progenies was intermediate to selfing and the longer distance pollinations, suggesting tight family clusters occur due to limited seed dispersal. Under this structure biparental inbreeding may be common, however, the cumulative impact of inbreeding seems negligible as relatedness did not appear to decline with distance between mates beyond 50 m.

Effects of inbreeding on population mean performance and observational variances in Eucalyptus globulus

Abstract• Mean performance and variances were studied in self (SELF), open pollinated (OP) and unrelated polymix (POL) crosses of common parentage in Eucalyptus globulus.• Inbreeding depression for survival (SURV) and basal area per hectare (BAH) was the highest reported for a SELF eucalypt population, increasing with age to reach 74 and 77%, respectively, over 10 years.• Inbreeding depression in the OP was 36% for SURV and 32% for BAH at age 10 years, and estimates of outcrossing rate from BAH were stable across ages, averaging 0.56. In contrast, OP inbreeding depression for stem diameter (DBH) of survivors decreased with age and few selfs appeared to survive to 10 years.• There was more variation in DBH between and within SELF than POL families, with variance ratios consistent with rare and partially recessive deleterious alleles causing inbreeding depression.• The OP variances were initially more similar to the SELF population but converged to the POL population after 10 years.• It is argued that when outcrossing rates are low, as in the present case, inbreeding depression will be a significant force countering local adaptation in forest trees.

The effects of age and environment on the expression of inbreeding depression in Eucalyptus globulus.

Inbreeding adversely affects fitness traits in many plant and animal species, and the magnitude, stability and genetic basis of inbreeding depression (ID) will have short- and long-term evolutionary consequences. The effects of four degrees of inbreeding (selfing, f=50%; full- and half-sib matings, f=25 and 12.5%; and unrelated outcrosses, f=0%) on survival and growth of an island population of Eucalyptus globulus were studied at two sites for over 14 years. For selfs, ID in survival increased over time, reaching a maximum of 49% by age 14 years. However, their inbreeding depression for stem diameter remained relatively stable with age, and ranged from 28 to 36% across years and sites. ID for survival was markedly greater on the more productive site, possibly due to greater and earlier onset of inter-tree competition, but was similar on both sites for the diameter of survivors. The deleterious trait response to increasing inbreeding coefficients was linear for survival and diameter. Non-significant quadratic effects suggested that epistasis did not contribute considerably to the observed ID at the population level. Among- and within-family coefficients of variation for diameter increased with inbreeding degree, and the variance among the outcrossed families was significant only on the more productive site. The performance of self-families for diameter was highly stable between sites. This suggests that, for species with mixed mating systems, environmentally stable inbreeding effects in open-pollinated progenies may tend to mask the additive genotype-by-environment interaction for fitness traits and the adaptive response to the environment.

Genetic variation and parental performance under inbreeding for growth in Eucalyptus globulus

Abstract• We aimed to better understand the genetic architecture of growth in E. globulus undergoing inbreeding by comparing families from selfing (SELF), open pollination (OP) and unrelated polymix crossing (POL) of common parents. Stem diameter at breast height (DBH) was assessed at 4, 6 and 10 years after planting in a field trial.• The OP heritability was overestimated at an early age relative to the POL heritability.• No significant correlations were found between the SELF and POL parental effects, indicating substantial non-additive genetic variation under inbreeding. The OP family effects were better correlated with the SELF than the POL population, and only at age 10 years, after substantial mortality of inbred progeny has occurred, was the positive correlation between OP and POL families significantly different from zero.• The estimated dominance variance arising from inbreeding was nearly 10-fold greater than the dominance variance associated with random mating and the additive variance, and appeared to be a major contributor to the variation in inbreeding depression amongst selfed families.

Identifying Deployment Zones for 'Eucalyptus camaldulensis' x 'E. globulus' and x 'E. grandis' Hybrids Using Factor Analytic Modelling of Genotype by Environment Interaction

Summary In this study we apply factor analytic methods to the analysis of diameter at breast height (DBH) at 3 years for 22 trials of 892 clones from four E. camaldulensis x E. globulus and six E. camaldulensis x E. grandis families established throughout Australia (Queensland, New South Wales, Victoria, Tasmania and Western Australia). Three factors were sufficient to describe the genetic variation in the data set and, on average, described 86% of the genetic variance within a trial. Estimated broad-sense heritability ranged from 0.05 to 0.85, and genetic correlation estimates between pairs of trials ranged from 0.09 to 0.99. Two-dimensional plots of factor loadings and cluster analysis of the estimated genetic correlation matrix indicated that the trials formed three groups that represent potential zones for deployment to maximise genetic gain. However, there was no geographic pattern in the distribution of the trials within these groups; further research is required to develop predictive models of the patterns in GxE for the germplasm and identify genotypes that are superior in each deployment zone.

Whole genome shotgun sequences for microsatellite discovery and application in cultivated and wild Macadamia (Proteaceae)

Premise of the study: Next-generation sequencing (NGS) data are widely used for single-nucleotide polymorphism discovery and genetic marker development in species with limited available genome information. We developed microsatellite primers for the Proteaceae nut crop species Macadamia integrifolia and assessed cross-species transferability in all congeners to investigate genetic identification of cultivars and gene flow. Methods and Results: Primers were designed from both raw and assembled Illumina NGS paired-end reads. The final 12 microsatellite markers selected were polymorphic among wild individuals of all four Macadamia species—M. integrifolia, M. tetraphylla, M. ternifolia, and M. jansenii—and in commercial macadamia cultivars including hybrids. Conclusions: We demonstrate the utility of raw and assembled Illumina NGS reads from total genomic DNA for the rapid development of microsatellites in Macadamia. These primers will facilitate future studies of population structure, hybridization, parentage, and cultivar identification in cultivated and wild Macadamia populations.

Rain Damage on Three Strawberry Cultivars Grown in Subtropical Queensland

In Queensland, Australia, strawberry (Fragaria × ananassa Duchesne) is grown in open fields and rainfall events can damage fruit. Following a rain event, damage was evaluated on three commercial cultivars. ‘Rubygem’ (80%) had more fruit damaged than ‘Strawberry Festival’ (55%) and ‘Camarosa’ (61%). “Etch,” where the surface of the fruit is eroded and, consequently, the seeds are raised relative to the damaged surface, was the most frequently occurring (>80%) damage type and was distributed on the body and tip of the fruit, while some fruit (<16%) showed cracking. Fully mature fruit was damaged (>80%) more than partially mature fruit, which differed between ‘Strawberry Festival’ (16%) and ‘Rubygem’ (68%). Cultivars that are resistant to rain damage would reduce losses and lower risk for the growers.

Modeling of genetic gain for single traits from marker-assisted seedling selection in clonally propagated crops

Seedling selection identifies superior seedlings as candidate cultivars based on predicted genetic potential for traits of interest. Traditionally, genetic potential is determined by phenotypic evaluation. With the availability of DNA tests for some agronomically important traits, breeders have the opportunity to include DNA information in their seedling selection operations—known as marker-assisted seedling selection. A major challenge in deploying marker-assisted seedling selection in clonally propagated crops is a lack of knowledge in genetic gain achievable from alternative strategies. Existing models based on additive effects considering seed-propagated crops are not directly relevant for seedling selection of clonally propagated crops, as clonal propagation captures all genetic effects, not just additive. This study modeled genetic gain from traditional and various marker-based seedling selection strategies on a single trait basis through analytical derivation and stochastic simulation, based on a generalized seedling selection scheme of clonally propagated crops. Various trait-test scenarios with a range of broad-sense heritability and proportion of genotypic variance explained by DNA markers were simulated for two populations with different segregation patterns. Both derived and simulated results indicated that marker-based strategies tended to achieve higher genetic gain than phenotypic seedling selection for a trait where the proportion of genotypic variance explained by marker information was greater than the broad-sense heritability. Results from this study provides guidance in optimizing genetic gain from seedling selection for single traits where DNA tests providing marker information are available.

Macadamia domestication in Hawai‘i

Macadamia is one of the few international food crops domesticated from the Australian flora. It was first described in Australia in 1857, but developed as a crop in Hawai’i following the First World War. Hawai’ian cultivars are responsible for the majority of the world production. This study reviews literature and archival documents to clarify the domestication pathway of this germplasm. Uncertainty about the accepted wild origin of the Jordan introduction, believed to be the main source of Hawai’ian cultivars, is highlighted. An unrecognised additional early introduction of M. integrifolia is identified, but its relevance to commercial germplasm is unknown. The Hawai’ian industry preference for M. integrifolia germplasm may have arisen because the kernels used to evaluate this species were sourced from poorly managed orchards. There is strong evidence that M. ternifolia, which produces bitter kernels, was also introduced at some stage. The advent of vegetative propagation was a major event supporting domestication. The origins of all named cultivars have been clarified and the similarity of two, Keaau and Mauka, has been highlighted. The pedigree of advanced generation selections is clarified indicating Keauhou was a common maternal parent. These results add to the heritage of the plant in both Australia and Hawai’i. In addition, knowledge of the pedigree of advanced selections can be used to improve prediction accuracy in analysis of breeding trials. Finally, improved knowledge of the domestication pathway will assist ongoing conservation and genetic improvement of the genus.

Correction to “Whole Genome Shotgun Sequences for Microsatellite Discovery and Application in Cultivated and Wild Macadamia (Proteaceae)”

Vol. 2 No. 4: 1300089, April 2014, doi: 10.3732/apps.1300089 The authors discovered an error in a primer sequence reported in Table 1. The corrected primer sequence (locus Mac0010, reverse primer sequence) is listed below in boldface. The authors apologize for the error. The published article (full-text and PDF) has been corrected.