Seedling Orchards Research Articles

Genomic evaluation for breeding and genetic management in Cordia africana, a multipurpose tropical tree species

BackgroundPlanting tested forest reproductive material is crucial to ensure the increased resilience of intensively managed productive stands for timber and wood product markets under climate change scenarios. Single-step Genomic Best Linear Unbiased Prediction (ssGBLUP) analysis is a cost-effective option for using genomic tools to enhance the accuracy of predicted breeding values and genetic parameter estimation in forest tree species. Here, we tested the efficiency of ssGBLUP in a tropical multipurpose tree species, Cordia africana, by partial population genotyping. A total of 8070 trees from three breeding seedling orchards (BSOs) were phenotyped for height. We genotyped 6.1% of the phenotyped individuals with 4373 single nucleotide polymorphisms. The results of ssGBLUP were compared with pedigree-based best linear unbiased prediction (ABLUP) and genomic best linear unbiased prediction (GBLUP), based on genetic parameters, theoretical accuracy of breeding values, selection candidate ranking, genetic gain, and predictive accuracy and prediction bias.ResultsGenotyping a subset of the study population provided insights into the level of relatedness in BSOs, allowing better genetic management. Due to the inbreeding detected within the genotyped provenances, we estimated genetic parameters both with and without accounting for inbreeding. The ssGBLUP model showed improved performance in terms of additive genetic variance and theoretical breeding value accuracy. Similarly, ssGBLUP showed improved predictive accuracy and lower bias than the pedigree-based relationship matrix (ABLUP).ConclusionsThis study of C. africana, a species in decline due to deforestation and selective logging, revealed inbreeding depression. The provenance exhibiting the highest level of inbreeding had the poorest overall performance. The use of different relationship matrices and accounting for inbreeding did not substantially affect the ranking of candidate individuals. This is the first study of this approach in a tropical multipurpose tree species, and the analysed BSOs represent the primary effort to breed C. africana.

A Roadmap for Participatory Chestnut Breeding for Nut Production in the Eastern United States.

Chestnut cultivation for nut production is increasing in the eastern half of the United States. Chinese chestnuts (Castanea mollissima Blume), or Chinese hybrids with European (C. sativa Mill.) and Japanese chestnuts (C. crenata Sieb. & Zucc.), are cultivated due to their high kernel quality, climatic adaptation, and disease resistance. Several hundred thousand pounds of high-quality fresh nuts are taken to market every fall, and several hundred additional orchards are entering bearing years. Grower-led on-farm improvement has largely facilitated this growth. A lack of significant investments in chestnut breeding in the region, paired with issues of graft incompatibility, has led many growers to cultivate seedlings of cultivars rather than grafted cultivars. After decades of evaluation, selection, and sharing of plant materials, growers have reached a threshold of improvement where commercial seedling orchards can be reliably established by planting offspring from elite selected parents. Growers recognize that if cooperation persists and university expertise and resources are enlisted, improvement can continue and accelerate. To this end, the University of Missouri Center for Agroforestry (UMCA) and chestnut growers throughout the eastern United States are partnering to formalize a participatory breeding program – the Chestnut Improvement Network. This partnership entails the UMCA providing an organizational structure and leadership to coordinate on-farm improvement, implement strategic crossing schemes, and integrate genetic tools. Chestnut growers offer structural capacity by cultivating seedling production orchards that provide financial support for the grower but also house segregating populations with improved individuals, in situ repositories, and selection trials, creating great value for the industry.

Micropropagation of zygotic embryos from genetically diverse almond seedling orchards in eastern Morocco

Numerous studies on perennial crops have shown that almond has a low tolerance to climate change, which led to detailed study for its adaptation by focusing on selecting heat-tolerant almond varieties. The long period of perennial agriculture creates particular challenges in a changing climate. The risk complicates the choice of a variety that the best variety for the current climate may be poorly suited for future climates. Hence the interest of having a large variability of tolerant genotypes. In the eastern Mediterranean region of Morocco, seedling almond trees are largely grown, which created an important gene pool, both for breeding programs and the selection of superior genotypes adapted to difficult pedo-climatic conditions. For the conservation of crop biodiversity in these almond groves, micropropagation is considered a feasible technique for producing and regenerating superior planting materials. Zygotic embryos of several local ecotypes of the almond native population known as ''Beldi'' were cultivated on Murashige and Skoog (MS) medium supplemented with different concentrations and combinations of auxins and cytokinins. The results showed multiple shoot initiation from zygotic embryos on MS medium containing 1mg/L of 6-Benzyl-aminopurine (BAP) combined with 0.5 mg/L of Indole butyric acid (IBA). A high rooting rate was obtained on a half-strength MS medium supplemented with 1mg/L of IBA.

Growth Performance of Uapaca kirkiana Müell. Arg Provenances in a Breeding Seedling Orchard in Malawi

Growth Performance of Uapaca kirkiana Muell. Arg Provenances in a Breeding Seedling Orchard in Malawi The population of Uapaca kirkiana Muell. Arg an indigenous fruit tree in southern and eastern Africa continues to decline due to deforestation, forest fragmentation and wildfires. Domestication of the fruit tree has been a priority to increase its genetic diversity and improve livelihoods of small scale farmers. The process of domestication of trees requires knowledge of ecological adaptive traits and intra-specific variation. A breeding seedling orchard comprising seven provenances was established at Bunda in Lilongwe the capital of Malawi in 2006. Growth performance was assessed through measurements in tree height, diameter at breast height (dbh), root collar diameter, number of branches and number of flowers for eight years. Results show that there are statistical significant differences (P ≤ 0.05) in height, diameter at breast height, root collar diameter among the seven provenances. Dzalanyama had the highest mean value for height and diameter at breast height ranging from 1.8 to 3.9 metres and 3.0 to 8.9 centimetres respectively, however a local provenance collected from within 5 kilometre radius of the test site showed the least growth performance suggesting that use of a local provenance does not always guarantee the best performance. Height was found to have high heritability values ranging from 0.31 to 0.43 while number of branches and number of flowers didnot appear to be under strong genetic control with heritability values of 0.12 and 0.08 respectively. The values for growth and genetic traits are from one site that could overestimate heritability values. Selection of provenances for tree improvement should be based on a combination of factors including seed quality and performance of provenances in multi-location trials.

Genetic parameter estimates for growth and form traits in common ash (Fraxinus excelsior, L.) in a breeding seedling orchard at Little Wittenham in England

Data from a trial of 36 families at Little Wittenham, North Oxford was used to assess growth traits and stem form in common ash (Fraxinus excelsior, L.). The trial followed a design described by Barnes (Silv Genet 44(2–3):81–88, 1995) as the Breeding Seedling Orchard (BSO). The objectives of the study were to determine variation in growth and form traits and estimate genetic parameters of families. Assessments conducted at 3–8 years for height, diameter at breast height (dbh), straightness and forking showed significant differences (P < 0.05) among families with Guys (19), Settrington (34), Overbury (23) and Grimthorpe (36) being the best performers while Coleford (3 and 5) Gwynedd (27) and Bacheiddon (32) were the least performers. At the overall level, the additive genetic coefficient of variation (CVA) ranged between 10.2 and 12.7% for height and 1.5 and 2.1% for dbh. Height had a high genetic correlation (rg = 0.85) with dbh whilst forking had low correlation (rg = 0.25) with height. Estimates of heritability decreased with age from \( {\text{h}}^{2}_{{\text{i}}}\) = 0.62 at 3 years to \( {\text{h}}^{2}_{{\text{i}}}\) = 0.30 at 8 years for height while values for dbh decreased from \( {\text{h}}^{2}_{{\text{i}}}\) = 0.48 at 4 years to \( {\text{h}}^{2}_{{\text{i}}}\) = 0.27 at 8 years. Some genetic gains are possible despite the low genetic variation among families; height had the greatest potential of genetic gain (12.5% at 8 years). Results suggest that early selection of superior families of Fraxinus excelsior appears to be feasible and it could be possible to achieve simultaneous improvement in both growth and form.

The impact of spatial heterogeneity on selection: a case study on Pinus pinaster breeding seedling orchards

Although failure to account for spatial autocorrelation has been dramatic in some forest progeny trials, little attention has been paid to how this issue may affect selections within the trials. The effects of spatial autocorrelation of height growth on the estimation of genetic gain and on the spatial distribution of the selected trees were studied in four Pinus pinaster Ait. progeny trials that were rogued using different selection methods and intensities. When selections are based on unadjusted original values, selected trees tend to be located in the best microsites and are unlikely to be the most genetically superior. This resulted in a loss of genetic gain that varied between 10% and 20% and sometimes exceeded 30%. Differences in the loss of gain among different selection methods and intensities were minor and followed no clear pattern. Selecting on the basis of a conventional model resulted in spatial patterns of the retained trees that were clearly aggregated in all cases. However, selections based on spatially adjusted data resulted in random spatial patterns, except with family selection because of the use of multiple-tree plots. Because clumping of the retained trees may seriously affect the quantity and quality of the seed crop, breeders are strongly encouraged to use appropriate spatial models for roguing breeding seedling orchards.

Acorn Fall and Weeviling in a Northern Red Oak Seedling Orchard

In 2000, we determined levels of damage by acorn weevils (Curculio spp.) and patterns of acorn fall in a northern red oak (Quercus rubra L.) seedling orchard in eastern Tennessee. The mean (±SE) production of acorns among 43 selected trees was 5,930 ± 586 acorns per tree with a maximum production level of 16,969 acorns for one tree. Trees were selected in the spring of 2000 based on abundance of acornets. The mean (±SE) damage level to acorns was 33 (±2) percent (determined by dissection). The floating method for assessing sound acorns overestimated acorn damage by 36 percent overall. Weevils accounted for approximately 66 percent of all damage to acorns. We found that the percentage of weeviled acorns was negatively correlated to total acorn production per tree. The rate of acorn drop was higher in October and November than in September. However, the percentage of acorns damaged by weevils was higher for acorns falling in September than for acorns falling in October or November.

Studies on ovulate strobili and seed production ofPinus patulain KwaZulu-Natal

Synopsis Cone and seed production studies in Pinus patula were conducted bythe Institute for CommercialForestry Research (ICFR) in KwaZulu-Natal as part ofthe improvement programme of the species. The optimum altitude for female strobilus and seed production is approximately 1450 m in KwaZulu-Natal. At four years after establishment of the Breeding Seedling Orchards (BSOs), male and female flowering is high enough to make a commercial cone collection two years later worthwhile. The seed potential is between 120 and 140 seeds per cone and seed efficiency about 50 percent.

Predicted and realized genetic gain inEucalyptus grandisbreeding seedling orchard in Zimbabwe

SYNOPSIS Results are presented of a fourth generation breeding seedling orchard of Eucalyptus grandis Hill Maiden of 30 half-sib families. Measurements at one and half and five years were available. Analysis of one and half year data showed no significant differences between the families for height, diameter at breast height, volume, and stem straightness but 5 year data showed significant differences for height, diameter, and volume but no significant differences emerged for stem straightness. Individual tree heritability (h2 b) estimates for height, dbh, volume, and stem straightness at 5 years were 0.20 ± 0.08,0.16 ± 0.19,0.12 ± 0.14, and 0.10 ± 0.09 respectively. Estimates of family heritability (h2 r) for height, diameter, and volume were moderately high (0.64 ± 0.15, 0.69 ± 0.11, 0.55 ± 0.28, and 0.30 ±0.13 respectively) but less so for stem straightness at five years. Predicted genetic gains in volume for family selection in E. grandis is 14.5% and estimates of realized genetic gains at the fourth ...

Pinus caribaea in China: introduction, genetic resources and future prospects

Pinus caribaea var. caribaea from Cuba was introduced to southern China in 1961 with P. caribaea var. hondurensis from Guatemala and P. caribaea var. bahamensis following in 1973. However, it was not until 1983 that combined variety/provenance tests were established on several sites with a range of provenances. It was reported that significant differences existed in quantitative genetic traits such as growth rate among the three varieties and P. elliottii which was used as a control. During the period from 1973–1978, 12 seed orchards or seed production areas of P. caribaea var. caribaea were established in Guangdong and Guangxi covering a total area of about 70 ha. All trees were grafted onto root stocks of P. elliottii or P. massoniana. Seed production was very low varying between 8–50 kg/ha on an annual basis. A combined provenance/progeny trial and gene bank of P. caribaea var. bahamensis was established in Guangxi in 1990 using seed provided by Oxford Forestry Institute with 14 provenances and 121 open-pollinated families representing the whole range of the variety. A breeding seedling orchard of P. caribaea var. caribaea was established in early 1995 in Guangdong Province using a multiple population breeding strategy. The main population consists of 220 families representing the natural stands and a selected population of a seed orchard in Cuba and land races developed in Brazil and China. It will be managed as a breeding seed orchard for genetic testing, selecting and seed production. There are six sub-populations subdivided by seed origins with open pollinated families varying from 16 to 75 in each. The total area of plantations of this species in China is now estimated to be over 40 000 ha. It is foreseen that Pinus caribaea could become even more important in plantation forestry in southern China and the area of this species could be expected to reach 100–150 000 ha by the year 2010.

Pinus patulaprogeny test: Heritability estimates and genetic correlations between fifth- and eighth-year traits

SYNOPSIS Seed for a breeding seedling orchard produced from a factorial mating design (33 progenies) and from a diallel (four progenies) was used to establish this progeny test. Analysis of fifth- and eighth-year data showed highly significant differences between the parents (females and males) for height, diameter and stem straightness. Three heritabilities were calculated. Individual tree heritability estimates of the half sib families of females ranged from 0,03 to 0,17 while those of males ranged from 0,14 to 0,52. Full sib individual tree heritabilities ranged from 0,14 for diameter at breast height (DBH8) to 0,32 for stem straightness (STRB) at eight years. Genetic correlations between traits for half sib families of females were as high as 0,94 for fifth- and eighth-year height while that of males was up to 1,00 for the same trait.

Eucalyptus genetic improvement in Madagascar

Eucalyptus improvement was initiated 20 years ago in Madagascar and aimed at selecting species and provenances adapted to the very diverse climatic conditions of the island. The present paper reviews the results obtained by interspecific, provenance, and progeny tests. The good adaptation of Eucalyptus grandis and Eucalyptus robusta was confirmed by various experiments. Malagasy provenances of both species exhibited poorer performance than those recently introduced from Australia. This is thought to be the result of a narrow genetic base and inbreeding. The results obtained from tests conducted in diverse environments indicate that E. grandis provenances are already well performing but exhibit limited variation. Provenances and progenies performances appear to be quite irregular and unpredictable on the basis of site as shown by the results presented here. Significant genetic differences exist among provenances of E. robusta tested for growth parameters. The analysis of variance revealed that genetic gain in volume production is possible through provenance selection. However, it is suggested to introduce a wider range of provenances of E. grandis and E. robusta for further evaluation and to select plus-trees within provenance rather than search for superior provenance. Tremendous variation in growth rate among trees offers great opportunity for further genetic improvement. It appears that there are remarkable provenance × site and progeny × site interactions. Future reafforested areas need to be planted with genetically improved material. Smallholder's ideotypes require that priority should be given to a few major selection criteria: growth rate and volume production, juvenile performance, coppicing ability and fire resistance. The priorities of the Madagascar genetic improvement programme are to pursue provenance introduction and progeny evaluation and to produce genetically improved material to be distributed on a large scale to village communities. It is suggested that these priorities be combined for cost efficiency. Evaluation of different provenances and progenies in diverse ecological areas, individual selection, and large-scale production of genotypes with a broad base is presently conducted in breeding seedling orchards to satisfy national needs for Eucalyptus spp. seeds using synthetic varieties.

Genetic improvement of non-industrial trees

Improvement strategies applicable to non-industrial trees with a clear focus on: end-use target group of beneficiaries, amount of planting material required, the biology of the species and the amount and structure of variation are discussed. Whichever strategy is used it is paramount that material is properly evaluated in trials and that diverse and productive germplasm is released. Cognizance of farmer's needs and criteria should be taken given that they are generally risk averse and try to stabilise production rather than solely maximise production. The consequences of release of planting stock need to be considered in relation to whether improvement will be recurrent or a single event. The establishment of breeding seedling orchards that perform the combined functions of resource population, breeding population, progeny test and seed production area would appear to offer distinct advantages. Decision strategies for improvement of non-industrial trees are discussed in relation to the features outlined.

Genetic variance of early height growth and expected gains from selection in a Minnesota population of black spruce

A genetic improvement project for black spruce (Piceamariana (Mill.) B.S.P.) was initiated in Minnesota in 1974, with an objective of improving the inherent growth rate of the local population. This study reports some field results from the initial phase of the project. Study objectives were to (i) estimate genetic and environmental variance components of early (age 10 years) tree height, (ii) estimate expected genetic gains from various selection methods in three seedling seed orchards and a clonal seed orchard, and (iii) evaluate the effect that these selection methods have on inbreeding levels in the rogued seedling orchards. Additive genetic variance accounted for 15 to 22% of the phenotypic variance in three wind-pollinated family tests and 10% of the phenotypic variance across the tests. Expected gains from combined-index (family and individual) selection in the family test - seed orchards (selection of 22 to 27%) ranged from 4.6 to 6.1%. Family + within-family selection and individual selection were 18 and 32% less efficient, respectively. Index selection resulted in the highest estimated levels of inbreeding in the rogued orchards. However, the largest difference between the various selection methods resulted in a difference in the average inbreeding coefficient of less than 0.15%. Based on this small difference, index selection could be used in roguing similarly designed seedling seed orchards with minimal risk of elevated inbreeding levels.

Studies on the apple sod culture I

1. In a too close planting apple seedling orchard in Aomori Apple Experiment Station, the growths of red clover under shady condition were investigated during the year 1949 and 1950, being compared with those in exposed field condion. Twenty Wagner pots were devoted to each block. 2. Until buds on the apple trees grew into the stage of “mouse-ear”, there had not been difference in the intensity of light measured with a rucksmeter between the too close planting orchard and the exposed field. After this, with the advance of flattening of apple leaves, the intensity of light in the orchard began to decrease, and in June when the leaves of the apple trees in the orchard completed their growth, it dropped to 50 per cent of the exposed field, the state continuing to fall. 3. In both these years, the decrease of the sun-light in the orchard had the corresponding growth of red clover, Thus, the harvest of red clover in the orchard was treated 20 days later than in the exposed field. But, concerning the height of red clover, the shady ones were taller than exposed ones. 4. In 1949, the green top weight of shady red clover was about 25 per cent of that grown in the exposed field; in 1950, at the frist harvest, 80 per cent, and at the second, 20 per cent. 5. As to those removed from pots, shady red clover showed about 20 per cent and 50 per cent of the growth of exposed ones in 1949 and in 1950.