Breeding Program Update

February 2016: by Eric Evans, Maine Breeding Coordinator

The current focus of our breeding program is to harvest seeds (B3-F2) from the most blight-resistant trees in our third-backcross (B3) orchards, and plant them in our seed orchards, which constitute the 5th generation of our 6-generation breeding program. After evaluation and selection for blight resistance and American type, the seed orchards will produce seeds (B3F3 – the 6th generation) for chestnut test and restoration plantings in Maine’s forests, starting in about 2020. We have two parallel and separate programs, named for the 1st-backcross tree that was the source of blight resistance – Clapper and Graves (the breeders who made the original Chinese-American crosses). Each program has 20-24 breeding lines planted in our 3rd backcross orchards, and each is producing seeds for a system of 9 seed orchards.

CLAPPER – Last spring we planted 4650 B3-F2 chestnut seeds (31 plots of 150 per plot) from our Merryspring (Camden) and Highmoor (University of Maine Experiment Station, Monmouth) B3 orchards into our seed orchards. This June we made final selections of the most blight resistant trees in the three breeding lines in our Mosher (Hope) orchard and the two remaining lines in Highmoor orchard #4 (Monmouth). Our harvest from these trees in October provided enough seeds for planting 13 new plots in our Clapper seed orchards this spring. Our October harvest totaled 9419 seeds from our Highmoor, Merryspring, and Mosher (Hope) orchards. This spring we will draw from these to establish 30 new plots of 150 seeds each in our Phippsburg, Searsport, and Stetson seed orchards. This will bring our total seed orchard plantings to 31,200 – well past the midpoint of our goal of 54,000 hybrid chestnut trees in our seed orchards by 2020.

GRAVES – The development of our Graves system is a little behind Clapper. In June we inoculated our Graves backcross orchards in Lovell and Morrill, and began the selection and culling process in our Veazie, Bradley, and Unity orchards that we inoculated last year. After we make final selections of the most blight-resistant trees there this June, we can collect B3F2 seeds for planting in our Graves seed orchards in Hartland and Winthrop in 2017. We will inoculate our youngest Graves backcross orchards in Unity and Hope in 2017, for planting the final new seed orchard plots in 2019-21.

Here is a summary of our seed orchard plantings:

ME Breeding Program Update TABLE 1: Seed Orchard Plantings

 

 

 

 

We expect to begin inoculating our seed orchards in Hartland this year with live blight fungus, to begin evaluation of their blight resistance. After selection and culling, we can collect B3F3 seeds for our first test plantings of potentially highly blight-resistant trees starting around 2020. This testing phase will continue for at least 10 years as the rest of our seed orchards go through the same process. We expect blight resistance to improve during that time, as the selections are refined based on initial testing results, and as more lines join the breeding population. Priority for getting trees for testing in the 2020s will go to members and volunteers. We give special thanks to all our orchard managers, and especially to our seed orchard managers – Glen Rea, Larry Totten, Bruce Probert, and Peter Bohman.

Breeding Program Update – August 2015

By Eric Evans, Maine Breeding Coordinator

The current focus of our breeding program is to harvest seeds (B3-F2) from the most blight-resistant trees in our third-backcross (B3) orchards, and plant them in our seed orchards, which constitute the 5th generation of our 6-generation breeding program. After evaluation and selection for blight resistance and American type, the seed orchards will produce seeds (B3F3 – the 6th generation) for chestnut test and restoration plantings in Maine’s forests, starting in about 2020. We have two parallel and separate programs, named for the 1st-backcross tree that was the source of blight resistance – Clapper and Graves (the breeders who made the original Chinese-American crosses). Each program has 20-24 breeding lines planted in our 3rd backcross orchards, and each is producing seeds for a system of 9 seed orchards.

CLAPPER – Last October we harvested over 9600 seeds from our Highmoor and Merryspring orchards. This spring we drew from these to establish 31 new plots of 150 seeds each in our Phippsburg, Searsport, and Stetson seed orchards. This brought our total seed orchard plantings to almost 27,000 – the midpoint of our goal of 54,000 hybrid chestnut trees in our seed orchards by 2020.

This June we made final selections of the most blight resistant trees in the three breeding lines in our Mosher (Hope) orchard and the two remaining lines in Highmoor orchard #4 (Monmouth). Our harvest from these trees this fall could be plenty to fill all our Clapper seed orchards to the original plan of 20 breeding lines.

GRAVES – The development of our Graves system is a little behind Clapper. In June we inoculated our Graves backcross orchards in Lovell and Morrill, and began the selection and culling process in our Veazie, Bradley, and Unity orchards that we inoculated last year. After we make final selections of the most blight-resistant trees there this fall or next spring, we can collect B3F2 seeds for planting in our Graves seed orchards in Hartland and Winthrop in 2017. We will inoculate our youngest Graves backcross orchards in Unity and Hope in 2016-17, for planting the final new seed orchard plots in 2019-21.

Here is a summary of our seed orchard plantings:

ME BREEDING Breeding Program update Table 2
We expect to begin inoculating our seed orchards next year, at age-4. After selection and culling, we can collect B3F3 seeds for our first test plantings of potentially highly blight-resistant trees starting around 2020. This testing phase will continue for at least 10 years as the rest of our seed orchards go through the same process. We expect blight resistance to improve during that time, as the selections are refined based on initial testing results, and as more lines join the breeding population. Priority for getting trees for testing in the 2020s will go to members and volunteers.  We give special thanks to all our orchard managers, and especially to our seed orchard managers – Glen Rea, Larry Totten, Bruce Probert, and Peter Bohman.

Breeding Program Update – January 2015

By Eric Evans, Maine Breeding Coordinator

The current focus of our breeding program is to harvest seeds (B3-F2) from the most blight-resistant trees in our third-backcross (B3) orchards, and plant them in our seed orchards, which constitute the 5th generation of our 6-generation breeding program. After evaluation and selection for blight resistance and American type, the seed orchards will produce seeds (B3F3 – the 6th generation) for chestnut test and restoration plantings in Maine’s forests, starting in about 2020.

In the spring of 2014 we planted 8,850 B3-F2 chestnut seeds from our Merryspring (Camden) and Highmoor (University of Maine Experiment Station, Monmouth) orchards into our seed orchards in Phippsburg, Searsport, and Stetson, bringing our total seed orchard plantings to 22,350. In October 2014, we harvested over 9,600 seeds from our Highmoor and Merryspring orchards. This spring we will draw from these to establish 33 new plots of 150 seeds each in our Stetson, Phippsburg, and Searsport seed orchards. This will bring our total seed orchard plantings to over 27,000 – the midpoint of our goal of 54,000 hybrid chestnut trees in our seed orchards by 2020.

Last June we injected live, lab-grown blight fungus into the bark of more than 200 trees (we call this “inoculation”) in our orchards in Veazie, Bradley, and Unity to begin the process of evaluating their blight-resistance. This year we will continue evaluation of blight resistance and American type, and expect to harvest more B3F2 seeds from our Monmouth, Camden, and Hope orchards. In the summer of 2015, we plan to inoculate trees in our orchards in Morrill and Lovell.

Breeding Program Update – June 2014

By Eric Evans, Maine Breeding Coordinator

The current focus of our breeding program is to harvest seeds (B3-F2) from the most blight-resistant trees in our third-backcross (B3) orchards, and plant them in our seed orchards, which constitute the 5th generation of our 6-generation breeding program. After evaluation and selection for blight resistance and American type, the seed orchards will produce seeds (B3F3) for chestnut restoration plantings in Maine’s forests, starting in about 2020.

Last spring we planted 7800 B3-F2 chestnut seeds from our Merryspring (Camden) and Deer Hill (China) B3 orchards into our new seed orchards in Winthrop, Hartland, Phippsburg, Searsport, and Stetson, bringing our total seed orchard plantings to 14,000. Last October we harvested over 14,000 seeds from 12 breeding lines in our Highmoor Farms B3 orchard in Monmouth (University of Maine Experiment Station). This spring we drew from these to establish 58 new plots of 150 seeds each, which brought our total seed orchard plantings to over 22,000 – approaching half of our goal of 54,000 hybrid chestnut trees in our seed orchards by about 2020. As in the first two years, we planted these seeds directly into the ground in April and May. This first planting from our Highmoor lines was only about half of our goal of 126 plots from those trees, so we will be nurturing those trees this summer, and returning to harvest there again this fall.

We are very pleased with the early growth of the seed orchard plantings. For example, the 2013 plantings in Searsport and Winthrop measured in November averaged 91% germination and survival, and the average seedling height is 17”. The survival of the trees from our first plantings in 2012 has been excellent, and some of them are over 6 ft tall.

In June we injected live, lab-grown blight fungus into the bark of about 120 trees (we call this “inoculation”) in both the Mosher B3 orchard in Hope and the remaining lines at Highmoor, to begin the process of evaluating their blight-resistance. This year we will begin culling, eventually keeping the best 2-4 trees in each breeding line. The trees that we select from this process will produce seeds for planting in our seed orchards starting in 2016. This year we expect to inoculate the trees in our orchards in Veazie, Bradley, Lovell, Unity, and Morrill.

Breeding Program Update – January 2014

Eric Evans, V.P. and Breeding Coordinator

The current focus of our breeding program is to harvest seeds (B3-F2) from the most blight-resistant trees in our third-backcross (B3) orchards, and plant them in our seed orchards, which constitute the 5th generation of our 6-generation breeding program. After evaluation and selection for blight resistance and American type, the seed orchards will produce seeds (B3F3) for chestnut restoration plantings in Maine’s forests.

Last spring we planted 7800 B3-F2 chestnut seeds from our Merryspring (Camden) and Deer Hill (China) B3 orchards into our new seed orchards, bringing our total seed orchard plantings to 14,000. Last October we harvested over 14,000 seeds from 12 breeding lines in our Highmoor Farms B3 orchard in Monmouth (University of Maine Experiment Station). This spring we will draw from these to establish 68 new plots of 150 seeds each in our seed orchards in Phippsburg, Searsport, and Stetson, which will bring our total seed orchard plantings to about 24,000 – approaching half of our goal of 54,000 hybrid chestnut trees in our seed orchards by about 2020. As in the first two years, we will plant these seeds directly into the ground in April and May. This first planting from our Highmoor lines will be only about half of our goal of 126 plots from those trees, so we will be nurturing those trees this summer, and returning to harvest there again this fall.

We are very pleased with the early growth of the seed orchard plantings. For example, the 2013 plantings in Searsport and Winthrop measured in November averaged 91% germination and survival, and the average seedling height is 17”. The survival of the trees from our first plantings in 2012 has been excellent, and some of them are over 6 ft tall.

In June we injected live, lab-grown blight fungus into the bark of about 120 trees (we call this “inoculation”) in both the Mosher B3 orchard in Hope and the remaining lines at Highmoor, to begin the process of evaluating their blight-resistance. This year we will begin culling, eventually keeping the best 2-4 trees in each breeding line. The trees that we select from this process will produce seeds for planting in our seed orchards starting in 2015. This year we expect to inoculate the trees in our orchards in Veazie, Bradley, Lovell, and Morrill.

Breeding Program Update – February 2013

By Eric Evans, V.P. and Breeding Coordinator

Back-cross Breeding Orchards: We planted the first of our 3rd-back-cross (BC-3) breeding orchards in 1999, and expect to plant our last one this spring. In fall of 2011 we harvested BC-3 seeds from trees in Orono, Bowdoinham, Augusta, and Wytopitlock. Last spring we planted seeds from three of these lines in our existing orchards in South Hope and Unity. We planted the rest in a nursery, and this spring we will plant these seedlings in a new orchard on Mary Bok’s farm in Hope, to raise our total to twelve BC-3 orchards.

Breeding Program Overview: We often talk about the chestnut breeding program being a “numbers game”. We need certain minimum numbers of trees in our breeding orchards to make sure that we can find lots of individuals with good blight resistance. And we need to include large numbers of wild chestnut trees in our breeding program to ensure the high level of genetic diversity that will give our Restoration® chestnuts the best chance of adapting to many environments and challenges in Maine forests in the coming decades and centuries.

In the next few years the Maine Chapter of TACF will be filling out our seed orchards with nearly 60,000 chestnut seeds. Why so many? And what will become of them all? To answer these questions we need a quick over-view of the TACF breeding program. TACF’s founders understood that blight-resistance of Chinese chestnuts could be added to American chestnut populations by using a six-generation “back-cross” breeding program. Starting with Chinese-American hybrids, the un-American Chinese characteristics are diluted in three generations of crossing back to pure Americans. Chinese chestnuts have an orchard tree form, whereas American chestnuts have a tall lumber-producing forest tree form that is desirable to preserve. And there are many other Chinese characteristics that we don’t want to introduce into our Restoration® chestnuts. At each backcross, the Chinese blight-resistance genes can be identified in a small percentage of trees, and saved for the next generation. Maine’s breeding program starts with pollen from selected second-back-cross trees (BC-2, generation #3) sent to us from the TACF research farms in Meadowview, VA. We pollinate native-ME American chestnut trees with this pollen to make third-back-cross trees (BC-3) for our breeding orchards – generation #4 in the six-generation program. When these trees are 6-8 years old, we evaluate their blight-resistance and American form, and then rogue out all but the best 5%. When these selected trees pollinate each other, 1/64 of the seeds (BC3-F2, generation #5) will have blight-resistance genes from both parents, and so should be as blight-resistant as the original Chinese great-great-great-grandparent. These are the seeds that we will plant in our seed production orchards.

Last spring we planted nearly 6000 BC3-F2 chestnut seeds in our first seed orchard plantings. And in the next 10 years, our seed orchard plantings will swell to 10 times that much, for a total of nearly 60,000 trees. Why these numbers? The purpose of the seed orchards is to produce Restoration® chestnut seeds for forest plantings that will be most likely to breed true for good blight resistance and American type – the culmination of our 6-generation back-cross breeding program. The seed orchards are planted in “units”. Each unit contains 20 plots, each with 150 seeds from each of 20 different breeding lines from our existing twelve 3rd-back-cross (BC-3) orchards. So each unit has 150 x 20 = 3000 seeds, gradually filled in over the coming 8-10 years as our BC-3 orchards mature and produce seeds. However, one such unit is not enough – to ensure success and keep a high level of genetic diversity in our final products, we plant nine replications of each seed orchard unit. And we need to double that number of units, because we have two parallel breeding programs, each from a separate source of Chinese chestnut blight-resistance. So the whole plan is to have 18 seed orchard units, each with 3000 seeds for an eventual total of 18 x 3000 = 54,000 chestnut trees. The seeds are planted just 12” apart in rows 7 ft apart, so a whole unit with 3000 seeds occupies about ¾ acre.

ME BREEDING Program Update table 3We will never have 54,000 trees to care for all at once, because we will be planting them over a 10-year span, and when each plot of 150 trees is 4-5 years old we will rogue out all but the best single tree. The time-line chart describes the progress of our breeding program in the coming years.

 

 

 

Seed Orchard Status: Our seed orchard plantings last spring consisted of 3-5 plots (out of an eventual 20) in each of 10 orchard units in Phippsburg, Hartland, and Stetson. Last fall we harvested enough seeds to expand these units with several additional plots, and start the remaining 8 units (of our total of 18) with these same breeding lines from our BC-3 orchards in Camden and China – a total of over 7500 seeds to plant this spring! These will include two more units on Penobscot County Conservation Association property in Stetson, and 6 new units on SWOAM (Small Woodlot Owner’s Assoc.) property in Winthrop and Searsport. We have completed the evaluation and selection of the trees in our BC-3 orchard at Highmoor Farms in Monmouth, and this year we expect to start this process in two more BC-3 orchards. The BC3-F2 seeds from these orchards will be available for planting into all 18 seed orchard units starting in 2014.

New Seed Orchard Sites : The Small Woodland Owners Association of Maine has very generously made available some of their property for the Maine Chapter to use for our chestnut seed orchards to be planted this spring. There is one site in Searsport where we will plant two seed orchard units, and two sites in Winthrop where we will plant four units. All of these sites are currently fields with soils well-suited to chestnut culture. Last fall we applied 3-ft-wide strips of landscape fabric in rows 7 ft apart, and then we will plant the seeds through holes in the fabric this April. Thank you SWOAM and PCCA!

Share This
Share on FacebookTweet about this on TwitterShare on TumblrShare on Google+Pin on Pinterest