Radiata Pine (Pinus radiata) Breeding Values
To assist growers in understanding what breeding and index values represent, TBA provides a brief summary and a more detailed explanation to assist.
A TBA seedlot or genotype will have Estimated Breeding Values (EBV's) provided to describe its genetic worth. The following table indicates the information provided and what it means:
|TREEPLAN run name||PRAD2020-02-27||TREEPLAN analysis (PRAD=P. radiata, 2020=year, 02=month, 27=day).
The later the year the better the predictions (improved models and more data) – only compare EBVs in the same TREEPLAN analysis.
|EBV heading||EBV value||EBV comments|
|National (Aus) Estimated Breeding Values (EBV) – Primarily used for breeding decisions but can also be used for deployment. A set of EBV's includes an $NPV value, and the 4 genetic traits impacting performance (growth=MAI, wood strength=STIFFNESS, branch size=BRANCH and log straightness=SWEEP).|
|NPV Aus 8%||$1351||NPV=Net Present Value, Aus=national index value, 8% = discount rate.
This represents the additional $NPV ($1351) per ha at harvest, this genotype/seedlot will provide for an integrated enterprise (growing and sawmill) using a national production system and an 8% discount rate. A single NPV for each seedlot/genotype allows ranking of genetic material (higher NPV=more profit) based on a set production system.
|MAI Aus ebv||2.81||MAI=Mean Annual Increment (growth), Aus=national ebv.
Aus MAI's are produced for the national breeding program. This represents the estimated breeding value of 2.81 m3/ha/yr above baseline production of 22.6 m3/ha/yr. Overall MAI for this seedlot/genotype = 25.41 m3/ha/yr (22.6 + 2.81). Used for comparative purposes against other seedlots/genotypes and also primarily for breeding decisions.
|BRANCH ebv||-0.91||BRANCH=Branch size in centimetres from baseline production of 5.5 cm. Smaller branch size provide smaller knots, and better profitability. This seedlot/genotype has an average branch size of 4.59 cm (5.5 - 0.91).|
|STIFFNESS ebv||0.45||Timber STIFFNESS in gigapascals (GPa) from baseline production of 11.3 GPa. Higher GPa = stronger wood for construction timber. This seedlot/genotype has an average STIFFNESS of 11.75 GPa (11.3 + 0.45).|
|SWEEP ebv||-1.21||Tree straightness (SWEEP) in millimetres per metre of stem from baseline production of 10.5 mm/m. Making the tree straighter should improve mill recovery and less SWEEP is better. This seedlot/genotype has an average SWEEP of 9.29 mm/m (10.5 – 1.21).|
|Regional NPV index values (NPV) and MAI EBV's – Primarily used for deployment decisions. A set of EBV's includes a $NPV value, and 4 genetic traits. As BRANCH, STIFFNESS and SWEEP do not change across regions, the national (Australia wide) ebv's for these traits apply, therefore only NPV$ and MAI are different.
CGIPP = Central Gippsland, CVic = Central Victoria, GTR = Green Triangle Region, MVal = Murray Valley, Tas = Tasmania, WA = Western Australia.
|NPV CGipp 8%||$1656||Regional $NPV are described similarly to the above NPV Aus 8% index, but using regional Mai ebv's to calculate the $NPV.
Generally the NPV will be higher for regions, as Australia wide results are primarily for breeding decisions whereas regional results are more useful for deployment. It’s the same seedlot/genotype but re-valued for use in a specific region.
|NPV CVic 8%||$1604|
|NPV GTR 8%||$1563|
|NPV MVal 8%||$1529|
|NPV Tas 8%||$1425|
|NPV WA 8%||$1564|
|MAI CGipp ebv||4.04||Regional MAI EBV's are similar to the MAI Aus ebv but reflect the MAI of each regional area when using the same seedlot/genotype. The same baseline of 22.6 m3/ha/yr applies. More appropriately used for deployment decisions as an additional indicator to the regional $NPV to understand predicted growth levels.|
|MAI CVic ebv||3.83|
|MAI GTR ebv||3.67|
|MAI MVal ebv||3.53|
|MAI Tas ebv||3.11|
|MAI WA ebv||3.67|
The genetic merit of a seedlot or genotype (tree) allows decisions when selecting material for use. TBA uses Breeding Values and Index Values to provide this comparative performance information. This lay person explanation is to quickly assist a decision maker to understand what the numbers represent and how they may be interpreted. There is significant science and statistical data behind the values produced and TBA can assist with a more detailed understanding.
TBA is seeking to improve performance over time by identifying genotypes (trees) with better characteristics (traits) for future use. TBA breeds new varieties and tests the genetic performance of individual trees (genotypes) over time and uses their performance as well as the performance of relatives to assist in predicting genetic worth.
An annual TREEPLAN genetic evaluation is undertaken to allow us to report the genetic merit of genotypes (or seedlots) for each trait we are seeking to improve. We use early age assessments to estimate the genetic worth of each trait at harvest. Environmental conditions and silviculture regimes will also impact actual performance achieved. We are interested in describing the genetic worth after using replicated experimental design to remove performance noise caused by environmental or silvicultural impacts.
Each seedlot or genotype (tree) is allocated an Estimated Breeding Values (EBV) for each trait of importance.
|MAI EBV (see note)||Mean Annual Increment||growth in cubic metres per hectare per annum|
|STIFFNESS EBV||GPa (Gigapascals)||stiffness in gigapascals - an indication of structural timber strength|
|BRANCH EBV||Branch size in centimetres||branch size which impacts size of knots in wood - smaller branches improves value|
|SWEEP EBV||Tree straightness in millimetres per metre||straightness of the trunk in millimetres per metre length - making the tree straighter and provide improved recovery through the mill process|
MAI note - TBA reports a national MAI EBV (MAI AUS EBV) for breeding decisions as well as other regionally based MAI performance for deployment decisions. These include Green Triangle Region (MAI GTR EBV), Tasmania (MAI TAS EBV), Western Australia (MAI WA EBV), Central Gippsland (MAI CGIPP EBV), Central Victoria (MAI CVIC EBV), Murray Valley (MAI CVIC EBV). Growers should utilise the most appropriate MAI based on their end use.
These EBV's provide a performance estimate for each trait, however when multiple traits are involved, decision making becomes more complex. Some traits can be negatively correlated, for example chasing growth can reduce wood strength, so a balance is needed.
TBA looks to maximise profit based on a defined production system (product end use). The production system identifies a single index value in Net Present Dollars (NPV) for improvements to each particular trait for the end use. As each improved trait has a profit value for each unit of improvement, TBA can then combine the value of each trait into a single $NPV index value for each seedlot/genotype. This single NPV index value estimates the genetic worth of each seedlot or genotype and the higher the NPV the more profitable the genotype for the specific end use modelled. It also allows all the genetic material in a TREEPLAN analysis to be assigned an NPV and rank the list from best to worst for a specific production system.
Recommendation 1: the higher the estimated $NPV for a seedlot or genotype, the better genetic merit of that seedlot or genotype for the specific production system (product end use).
It should be noted that TBA uses a national production system to allow the breeding program to identify new elite material for use, so an NPV index for AUS describes the genetic material. TBA can also provide regional or customised production systems for use by growers depending on their end use and economic objectives. Therefore it remains important to understand the underlying production system being used to establish the NPV index value and if comparing seedlots or genotypes for use, you need to compare them using the same underlying production system.
An annual TREEPLAN analysis is undertaken using all the historical data and any new performance data collected in the last year to re-describe the genetic worth of each genotype.
Recommendation 2: identify the year of the TREEPLAN analysis and use the latest TREEPLAN run as more data and refined models may improve the predictions.
Recommendation 3: To avoid comparing apples and oranges, only compare breeding values if they are derived from the same TREEPLAN analysis.
For Australia (national) use, we currently predict breeding values against a national baseline productivity as provided in the following table. Some clients have developed customised baseline production models to suite their plantations and describe the genetic worth against their own models and the average baseline values may be different to the TBA nation baselines used. The same baseline productivity estimates are used for regional EBV's reported.
Radiata pine - national baseline production model
|Traits reported||Baseline productivity||Comments|
|MAI (m3/ha/yr)||22.6||Average growth or volume in cubic metres per hectare per year at rotation harvest|
|STIFFNESS (GPa)||11.3||Average stiffness in gigapascals - an indication of the wood quality for use in construction (strength)|
|BRANCH size (cm)||5.5 (lower is better)||Average branch size in centimetres which impacts knot size in the wood - small branch size means more profitable wood|
|SWEEP (mm/m)||10.5 (lower is better)||Average curve of the trunk in millimetres per metre length - making the tree straighter and provide improved recovery through the mill process|
The systems we use to predict EBV's are flexible to accommodate different users and different productivity systems. This allows us to rescale the EBV's depending upon user needs.
To understand the EBV for each individual trait, we report the genetic difference of the genotype or seedlot and not the total productivity. For example, with growth (MAI), an MAI Aus EBV of 3 means the genotype/seedlot will be 3 units better than the baseline level of production. TBA reports against an average baseline of 22.6 m3/ha/yr meaning an average growth rate of 22.6 cubic metres per hectare per year and any reported MAI Aus EBV variance will be above (or below = negative) this baseline. Therefore with an MAI Aus EBV of 3, this genotype has a total predicted MAI of 25.6 (22.6 + 3). The baseline production can vary depending on the EBV's being reported and it remains important to understand the baseline being used for each trait.
Recommendation 4: If you are looking to appreciate each traits worth at harvest (rather than just its genetic comparison with other seedlots), seek the baseline production values and their foundation (is it national, region, site type, etc) and if it is related to the area you intend to grow the material.
Traits can be negatively correlated, so chasing growth alone may reduce other traits and the resultant logs may not maximise profit. Each genotype/tree/seedlot has average EBV's for its production but generally, a grower is trying to improve profit, which is trying to identify the best combination of traits together for their production system. We provide an $NPV for each genotype or seedlot so users can compare the merit of material in the same analysis but it must be noted that the $NPV is directly related to the production system defined and end use. A grower may be selling his wood for fence posts, so his end use is different to grower selling wood for structural housing use. The production model and $NPV will be very different as the fence post producer may only chase growth (MAI) and not be interested in wood strength (STIFFNESS) so the economic model would be set up to recalculate the $NPV index and re-sort the rankings of genotypes with better characteristics for that specific use.