From The University of Florida Cooperative Extension Service CIR 1190: Genetically Improved Pines for Reforesting Florida’s Timberlands1 Timothy L. White and Mary L. Duryea2 Genetically improved varieties of pines can increase the productivity and health of reforested timberlands in Florida. Just as farmers plant specific varieties of crops that have been developed through many cycles of breeding and testing, so too forest landowners need to obtain the best-available pine variety for reforestation of their lands. Introduction Breeding programs of trees involve four main steps: 1) Selection of superior trees—called plus-trees—from natural stands; 2) Grafting of these superior plus-trees into seed orchards that produce genetically improved seed; 3) Field testing of these plus-trees to identify the the best trees and improve the orchard seed by removing inferior trees; and 4) Continued improvement and development of still-better varieties through interbreeding of the best trees. When a landowner decides to regenerate a site with pines there are two genetic decisions to make: 1) Selection of the appropriate pine species and 2) Selection of the best available genetic variety of that species. When ordering genetically improved seedlings from Florida’s forest tree nurseries, landowners need to inquire about the degree of genetic improvement. Seedlings with more advanced breeding will generally grow faster and be more disease-resistant in the planted forest, and some nurseries have better varieties available. Tree breeding has the same goal as animal and plant breeding: to develop genetically-improved planting stock of forest trees that produce healthier, higher-yielding plantations (see Table 1. Glossary). An additional goal of tree breeding programs is to maintain a broad genetic diversity within each new variety to help buffer the variety against the varied environments of a long plantation life. Tree breeding programs began in the 1950s in the southeastern United States and have developed genetically-improved varieties of loblolly pine (Pinus taeda L.), slash pine (Pinus elliottii Engelm. var. elliottii), longleaf pine (Pinus palustris Mill.), and sand pine [Pinus clausa (chapm. Ex Engelm.) Vasey ex Sarg.]. Use of these new varieties is not intended to replace the utilization of quality-grown nursery seedlings, or as a substitute for good site preparation and appropriate silvicultural treatments of the plantation. However, genetically improved seedlings when used in combination with these silvicultural methods, can greatly increase plantation growth and yield. The objectives of this document: 1) Describe the nature and scope of tree breeding programs in the southeastern United States; 2) Highlight the 45-year program to develop genetically-improved varieties of slash pine; and 3) Summarize the status and availability of these pine varieties to Florida landowners. 1. This document is CIR 1190, one of a series of the School of Forest Resources and Conservation, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida.. Published: June, 1997. Please visit the FAIRS Website at http://hammock.ifas.ufl.edu. 2. Timothy L. White, Ph.D. and Mary L. Duryea, Ph.D., professor and associate professor, School of Forest Resources and Conservation, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611. The Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, color, sex, age, handicap, or national origin. For information on obtaining other extension publications, contact your county Cooperative Extension Service office. Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences / University of Florida / Christine Taylor Waddill, Dean Genetically Improved Pines for Reforesting Florida’s Timberlands Page 2 Table 1. Glossary of Tree Improvement Terms Nature and Scope of Tree Breeding Programs Like breeding programs of plants and animals, tree breeding programs involve several steps (described more fully in the section Development of genetically improved slash pine varieties). The physical size and long-lived nature of forest trees means that these steps are both costly and time-consuming. Thus tree breeding programs have not progressed as rapidly as those of major crops and animals, though the principles of the programs are identical. The cost and nature of a tree improvement program make it virtually impossible for small, private landowners to conduct their own programs. Even large forest products companies find it difficult to go it alone. This has led to unique structures—tree improvement cooperatives— composed of large companies, state agencies and universities pooling their resources and working together to develop genetically improved varieties of pines for their region. This arrangement of breeding cooperatives has been a cost-efficient way to develop varieties that are available to both large and small landowners. Currently in the southeastern United States, there are 30 companies and state agencies from 11 states participating in three of these breeding cooperatives 1.0, 1.5, etc. Symbol to describe the extent of breeding by referring to the generation of breeding breeding value Degree of genetic superiority of a clone in a seed orchard as estimated from the performance of its seedling offspring in field progeny tests clone A group of trees with the same genetic make-up first-generation of selection The first group of trees which are selected from the wild forest; the symbol 1.0 is used to describe the first generation genetic gain The improvement in volume of a variety at time of harvest—usually expressed as % yield above use of wild, unimproved seed genetic/tree improvement Applying knowledge of genetics to improve tree growth and health genotype The genetic or hereditary make-up of a tree phenotype The external appearance of a tree resulting from both genetic and environmental influences plus-tree A tree selected on the basis of its outstanding external appearance in the native forest, but as yet untested at multiple locations to determine the exact extent of its superiority progeny test A field test that compares and ranks superior plus-trees over a range of environmental conditions roguing Removing underperforming trees from the seed orchard rootstock A root system onto which the scion of the plus-tree is grafted rust resistant A clone, plus-tree, family or variety less susceptible (though not immune) to the disease caused by the fusiform rust fungus scion A branch tip cut from a plus-tree and grafted onto a rootstock plant in a seed orchard seed orchard A central location where plus-trees are grafted and cultured to produce genetically improved seed tree breeding The science of changing the genetic make-up of a population of trees through sexual reproduction and selection variety A group of genotypes grafted into seed orchards for the purpose of producing genetically improved seed June 1998 Genetically Improved Pines for Reforesting Florida’s Timberlands Page 3 housed at the University of Florida, North Carolina State University and Texas A & M University. Together, these organizations annually produce more than 1.3 billion genetically improved pine seedlings—enough to reforest nearly 2 million acres each year. More than 90% of all pine reforestation in the southern United States utilizes genetically improved seedlings. This number includes those non- industrial landowners who purchase the genetically improved seed of these new varieties from nurseries. Development of Genetically Improved Pine Varieties: A Case Study of Slash Pine All breeding programs are continuous in the sense that they strive to develop new and better varieties across time. Breeding programs of trees involve four main steps: 1) Selection of superior plus-trees from natural stands; 2) Grafting of these superior plus-trees into seed orchards that produce genetically-improved seed for reforestation; 3) Field testing of these plus-trees to quantify their superiority and improve the genetic quality of seed orchard seed through removal of inferior trees; and 4) Continued improvement and development of still better varieties through controlled interbreeding of the best trees to form varieties that combine the superior attributes of these plus-trees. The steps of a tree breeding program will be briefly described for the development of genetically improved slash pine by the Cooperative Forest Genetics Research Program (CFGRP). The CFGRP is composed of 11 companies, the state forestry agencies from Florida and Georgia, and the School of Forest Resources and Conservation (SFRC) of the University of Florida. These organizations began cooperating in the early 1950s and continue to work together as described here. Step 1: Selection of Superior Plus-Trees The slash pine breeding program began 45 years ago with the selection of large, straight, disease-free trees from the natural range of slash pine in Florida, Georgia, Alabama, Mississippi and South Carolina (Figure 1). Figure 1. An example of a plus-tree in a natural forest stand of slash pine, selected for its large size, straightness, good form, and healthy appearance. June 1998 Genetically Improved Pines for Reforesting Florida’s Timberlands Page 4 Each industrial and state member of the University of Florida’s CFGRP made approximately 200 of these plus-tree selections from their forests. In total, more than 2,500 slash pine plus-trees were selected to provide broad genetic diversity from the entire natural range of slash pine in the five southeastern states. Especially important has been the selection of 500 disease-free trees from stands heavily infected with the fungal disease called fusiform rust [Cronartium quercuum (Berk.) Miy. ex Shirai f. sp. fusiforme]. This disease causes losses of timber valued at more than $35 million annually. The 500 disease-free trees selected in heavily infected stands have proved to be more resistant— though not immune—to damage by this fungus. Figure 2a. Branch tips (scions) are collected from each of 40 to 100 plus-trees Similarly, more than 190 disease-free trees have also been selected in forests that were heavily infected with the second most important disease of slash pine called pitch canker [Fusarium subglutinans (Wollenw. & Reink.) Nelson, Toussoun and Marasas comb. nov.] In total, the 2,500 plus-trees selected in slash pine from the entire natural range form a genetically diverse base for the long-term breeding program. Step 2. Formation of Grafted Seed Orchards After selection, 20 to 40 branch tips were obtained from each plus-tree by shooting or climbing and cutting branches. These branch tips—or scions— were then grafted onto rootstock that had been planted in a central location called a seed orchard. See the following figures: Figure 2a; Figure 2b; Figure 2c; Figure 2d. . Figure 2b. These scions are grafted onto rootstock that have been previously planted into the seed orchard. June 1998 Genetically Improved Pines for Reforesting Florida’s Timberlands Page 5 Figure 2c. The grafted trees mature and inter-pollination occurs among the superior clones in the orchard. Figure 2d. The improved seed is used by nursery managers to grow improved seedlings for reforestation. The scions from each plus-tree have the exact genetic make-up as the plus-tree from which they were obtained. By grafting scions from each plus-tree into a seed orchard, exact copies of that plus-tree are created and these copies together form a clone of the plus-tree. This is how seed orchards produce genetically superior seedlings. Multiple copies of each plus-tree are needed to produce sufficient quantities of seed for reforestation. By bringing together superior clones selected throughout the natural range, the seed produced from the seed orchard will be formed by the inter-pollination among these clones. This seed will contain the genes from the superior clones, and therefore produce genetically improved seedlings that grow faster and are healthier than unimproved seedlings from wild seed. Nursery managers sow the improved seed in forest nurseries, and these genetically improved seedlings can be purchased for reforestation. In the 1960s, each cooperating CFGRP member grafted its 40 to 100 selected clones into a seed orchard. These original seed orchards are called first- generation, unrogued seed orchards because the selections came from the first generation (1.0 generation) of selection and their genetic quality had not yet been established by field testing in plantations. In the 1970s, as the first-generation orchards developed and began to produce improved seed, each member used seed from its own orchard for the reforestation of company timberlands. Two state agencies (Florida Division of Forestry and Georgia Forestry Commission) used the improved seed in state nurseries making the improved seedlings available to non- industrial landowners. Each of the CFGRP members had a different set of 40 to 100 selections in its original seed orchards (their own selections), and so the genetic quality and expected level of improvement varied among the seed orchards of the members. On average, the expected improvement from 1.0 unrogued seed orchard was approximately 9%, meaning that forests planted with seed from these varieties were expected to yield 9% more volume at harvest compared to forests planted with unimproved seed collected from wild stands (Table 2). Note: Seed from 1.0 unrogued varieties is no longer used for reforestation, since better varieties are now available as explained in the next section. June 1998 Genetically Improved Pines for Reforesting Florida’s Timberlands Page 6 Table 2. Types of slash pine varieties, their years of use, and genetic gains (in % volume yield/acre above unimproved material when the trees are 20 years old). These gains are averaged from actual CFGRP seed orchards of different levels of genetic improvement. Low- and high-hazard sites are those with little versus high incidence of fusiform rust. Years of Use Orchard Type Genetic Gain (% volume yield) Low -Hazard Sites High-Hazard Sites Average 1900-1970 Unimproved 0.0 0.0 0.0 1970-1990 1.0 Unrogued 7.6 12.9 8.8 1980-1995 1.0 Rogued 12.8 17.9 14.0 1985-2005 1.5 Unrogued 17.1 22.5 18.3 2000- 2.0 Unrogued 22.0 28.0 25.0 Step 3: Field Testing to Quantify Genetic Superiority The original plus-trees chosen from natural stands were selected solely on the basis of their external appearance, called the phenotype. The phenotype is influenced by many factors including the tree's growing environment, soil microsite, and genetic make-up. Some of the 2,500 plus-trees selected in natural stands had superior phenotypes mainly due to fertile soil pockets, more light, or other favorable environmental conditions where they were growing. Other plus-trees were more genetically superior than their outward appearance indicated. To quantify the genetic superiority of each plus- tree, it was necessary to create field tests (named progeny tests) in which a plus-tree's seedlings’ performance—growth and disease-resistance—was used to judge the genetic value of the parent. Simply put, if a plus-tree's offspring perform well over a number of soil and climatic conditions, that reflects well on the plus-tree. The members of the CFGRP planted more than 400 progeny tests to judge the genetic worth of each of the 2,500 selected slash pine plus-trees. These plantings began in the mid-1970s as follows: 1) Seed was collected from the grafted trees (scions of each plus-tree) that were growing in seed orchards; 2) The seed from each plus-tree was kept separate and grown in nurseries to produce seedlings; 3) The seedlings from 25 to 150 plus-trees were planted in any given field experiment called a progeny test and resembling a forest plantation; 4) Over several years, the seedling offspring of a given plus-tree were planted in from 1 to 20 different field progeny tests with a range of soil and climatic conditions; 5) The 400 progeny tests were maintained and the trees measured for growth, disease damage and other traits; and finally, 6) The data from these nearly 500,000 trees (the seedling offspring from 2,500 plus-trees) were used to rank the 2,500 plus-trees for several growth and disease resistance traits. These rankings were used two ways to increase the genetic superiority of the slash pine varieties available for reforestation. First, the original 1.0 generation seed orchards were rogued by removing inferior plus-trees so that only the proven-superior plus-trees were allowed to remain and contribute pollen and seed in the rogued orchard. Second, at the beginning of the program, companies formed their 1.0 orchard from plus-trees selected on their timberlands. After progeny testing, they began to exchange plus-trees with other companies in the CFGRP cooperative to obtain the very best 50 or so plus-trees. These new orchards, called 1.5 generation orchards, have higher genetic gain than 1.0 orchards June 1998 Genetically Improved Pines for Reforesting Florida’s Timberlands Page 7 because the 50 progeny-tested trees grafted into these orchards are the cream-of-the-crop not just from a single company’s own plus-trees (40 to 200), but rather from the entire cooperative effort (2,500 plus-trees). Step 4: Continued Improvement and Development As with breeding programs of plants and animals, tree breeding programs inter-mate superior genotypes and screen their offspring to locate new selections that combine the best attributes of both parents. This controlled breeding is done by control pollination which involves taking the pollen from one superior parent and placing that pollen on the female flowers of a second parent. The seedlings produced from such a mating are full-siblings (because they have the same mother and father). These seedlings receive half of their genetic make-up from each parent, but are not identical genotypes just as human brothers and sisters are different. The goal is to search among the offspring for the individuals that received the best genes from their parents. In the CFGRP, members began making control pollinations among superior genotypes in the 1970s. More than 1,000 of the best first-generation selections were chosen as parents for this breeding based on the performance of their progeny in the progeny tests. These 1,000 parents were then inter-mated in many different combinations —for example, a good grower with a good grower; a good grower with a very rust resistant parent, etc.—to form more than 2,500 different full-sib families. These families were planted out in field progeny tests in forest plantations. Altogether more than 400 progeny tests (different members planting at different locations in Florida, Georgia, Alabama, Mississippi, and South Carolina with more than 500,000 trees being planted. These field trials were managed like normal pine plantations and each tree measured at ages 5 years and 8 years for its growth rate and disease status. In 1985-87, cooperative members used the information from these progeny tests to select the 1,000 best trees. These 1,000 selections are called second- generation (2.0) selections because they are the very best offspring (combining fast growth and disease resistance) from the very best first-generations selections. These 1,000 second-generation selections form a genetically diverse, yet more advanced, population of slash pine to continue the breeding program. Many members of the slash pine breeding cooperative used the very best 30 to 60 of the 1,000 second generation selections to graft into a new clonal seed orchard. These 2.0 seed orchards—grafted between 1987 and 1995—and will produce commercial quantities of seed about 8 to 10 years between 1995 at the earliest and 2005 at the latest. Plantations established with seed from these orchards will have excellent genetic gain—more than 25% increased yield above unimproved varieties (see Table 2)—with broad genetic diversity. Choosing Genetically Improved Seedlings for Reforestation When landowners decide to regenerate a site with pines, there are two genetic decisions to make: selection of the pine species, and selection of the best available variety of that species. Selecting the Pine Species The matching of the right pine species to the right site is a critical first step. Off-site plantings of a species can result in mortality or stagnated growth. For example, there have been several plantings of slash pine on sandhill sites that grew poorly because the planting site was not a slash pine site. The selection of species is based on soil characteristics (texture, drainage), final products desired (pulpwood vs lumber), silvicultural plans (such as bedding and fertilization) and the presence of diseases and insects (especially fusiform rust, pitch canker, southern pine beetle and brown-spot needle blight). Landowners should observe their neighbors’ forest plantations to see what species are doing well and should consult a professional forester to determine the best species to plant on their site. The majority of pine seedlings planted in Florida are bareroot although some containerized seedlings (especially longleaf pine) are available. Forest tree seedlings may be purchased at any of Florida’s forest tree nurseries (Table 3). Seedlings should be ordered from Florida nurseries between July 1 and December 31, although in many years supplies have run out by December. June 1998 Genetically Improved Pines for Reforesting Florida’s Timberlands Page 8 Table 3. Florida’s forest nurseries where seedlings can be purchased. Andrews Nursery, Florida Division of Forestry PO Drawer 849, Chiefland, FL 32644-0849 Phone: 352-493-6096 Buckeye Nursery Inc PO Box 450, Perry, FL 32347 Phone: 904-584-0231 Central Florida Lands & Timber Rt 1 Box 8899, Mayo, FL 32066 Phone: 904-294-1211 Dees Tree Farms & Nursery Rt 1 Box 752 Mayo FL 32066 Phone: 904-294-1512 Dwight Stansel Farm & Nursery 5553 164th St, Wellborn, FL 32094 Phone: 904-362-2617 Jefferson Smurfit Corp PO Box 129, Archer, FL 32618 Phone: 352-495-2660 Keen Forest Management Rt 1 Box 782, Mayo, FL 32066 Phone: 904-294-2234 St Joseph Land & Development Co Route 1 Box 70, Lamont, FL 32336 Phone: 904-997-3736 Superior Trees Inc PO Box 9325, Lee, FL 32059 Phone: 904-971-5159 Nurseries will usually describe seedlings as “Improved” for slash, loblolly, sand and longleaf pines or “Improved Rust-resistant” for slash and loblolly. “Improved” means the seed came from a first generation (1.0) or more advanced seed orchard. Yet, for several reasons, not all “Improved” varieties have the same genetic superiority. First, the type of seed orchard (1.0 unrogued, 1.0 rogued, 1.5 and 2.0) implies the level of improvement, and more gain, on average, is expected from increasing levels of improvement; refer to Table 2. Second, there are many varieties within each level of improvement because different organizations compose their seed orchards with different plus-trees. Example: an organization with high hazard fusiform- rust lands may use more rust-resistant plus-trees, but fewer high-growth plus-trees. Selection of the Best Available Variety Unlike agronomic crops, there is no standard way of naming varieties of pines that describes to the buyer

Deep green needles, 5"+; 6" cones; a source of pulp, timber, rosin, and turpentine; native to the southeast U.S. Improved for Timber Production.