Thursday, October 16, 2014

Lessons In Persistence

Lessons In Persistence:
Breeding for Rust Resistance

An Interview With Ron Reimer
Part 1

 Ron in his garden in Russellville, Arkansas

Since Ron has just this fall made his first series of introductions for 2015, I am rerunning the two-part series on his breeding program that I published in 2013. To see Ron's new introductions, CLICK HERE. To go to part 2 of this series, CLICK HERE.

Ron has also asks me to add a bit of new information to the beginning of this post concerning his current rust resistance ratings and views on resistance.

"Our past several years have given us extremely bad rust infestations.  This year was by far the worst due to repeated small rains and high humidity with heavy dew throughout the season.  This is unusual for us as we usually bake in high heat and drought for the summer.  This year's weather conditions were so conducive to rust infestation that it provided a super-acid test for rust resistance.  Lots of downgrading in the rust ratings had to be done, I'm afraid, and many outstanding cultivars got a blue tag, which is ultimately a ticket to the compost heap.  This too is part of the program, keeping a small population of rust prone plants handy in the garden, but not too many. On the bright side, many cultivars have remained free of rust throughout the season."

"The University of Georgia discovery of many strains of rust have prompted me to qualify my labels of rust resistant and high rust resistance.  On my photo gallery I have indicated that I cannot claim total immunity to rust; it is just more complicated now.   I still do have totally rust free daylilies in a rust infested garden, but I am less certain about their immunity in the face of uncertain climate and the multiple rust strain question." 

Ron's current rust rating system 10/20/2014

This is the first of a two part series on the breeding work of Ron Reimer of Russellville, Arkansas. In this first part, we will look at Ron’s breeding efforts toward producing a line of rust resistant diploid daylilies and in the second part, we will look at the products of his work thus far and the direction he is pursuing in developing a line of resistant daylilies of distinct phenotype for future introduction to the public.

In my pursuit of information on breeding for rust resistance in daylilies, I have found little information that is very useful and what information that is out there that is useful has been hard to find and has required a considerable amount of sleuthing to uncover. In general, when one is seeking to breed for a given trait, you turn to both breeders and researchers to gain knowledge of practical selection methods and academic and industry research. However, in the daylily world and the academic and industry setting, very little has been done, either in terms of practical breeding efforts or applicable research. So it was that I was very happy to begin to read posts on the daylily main Internet robin by such people as Matthew Kaskel and Ron Reimer. Matthew had pursued breeding for rust resistance in tetraploids, while Ron Reimer has pursued the same in diploids. I soon learned that Mr. Kaskel is no longer breeding daylilies, so that left only Mr. Reimer for me to communicate with about an active program.

I contacted Ron Reimer in late 2011 and began to actively communicate and over that time, I have been lucky to be able to ask him many questions about his program. What follows is information that has been collected from some of his robin posts as well as through our many conversations, when I have been able to pose many questions on his program. As I have over twenty years experience in breeding for resistance to various diseases in animals, I was able to pose many questions that gave me good insight into his program and helped to confirm to me that Ron has indeed developed rust resistance to a high level in his project lines.

To begin with, let’s look at how Ron got started with this project and a bit on his background with plants and plant breeding. In his own words, Ron says, “My horticultural background goes back to when I was about eight, visiting with local breeders and nurseries in the San Francisco Bay area.  I started to raise orchids when I was twelve and only stopped when I left Santa Barbara at age 35.  My degree is in Horticulture and Landscape Architecture.  I designed and installed landscapes for most of my life. Plant breeding has always been my first love…For many years, orchids and later here in Arkansas, apricots, crape myrtles, daffodils, and azaleas and last, but not least, daylilies.  I started hybridizing daylilies in 1989 with the idea of producing strong superior garden-performing plants. I had been working with both Dips and Tets, but preferred Dips.  My goals were to develop very large, wide-segmented, heavy-textured, flat-opening and flat-formed flowers.  I pursued early morning openers with clear very strong colors (like impatiens), which were free from Spring Sickness and root rot.  All colors of flowers must perform in our hellish summer climate and still look good at 8:00 p.m.

“I was close to introducing several Tets from my own converted seedlings when Rust appeared.  It was very devastating to see so many cultivars come down with Rust.  One bright spot, however, was that many of my Dip seedlings were resistant even under extreme Rust conditions. Very few Tets showed any Rust resistance, so I decided to work with Dips. My direction from 2002 on, to breed rust resistant seedlings, started with diploids that were already generations away from their named parents.”

Ron working with his daylilies

So to more fully understand the lines that Ron has developed, I felt it important to find out what those diploid seedlings he was working with had originated from. This I felt was important, as I am of the opinion that rust resistance factors are heritable and I had noted in various rust research evaluations and surveys, that certain family lines consistently popped up. So I enquired about the origins of the dip seedlings that Ron began his resistance breeding from. Here is his informative reply.

The most influential daylily in my program was Carpenter's MERLE KENT MEMORIAL, which unfortunately is a tender evergreen.  What I did with that plant is representative of the way my seedlings have been developed.  I selfed MKM and the result was a very wide range of colors, all with perfect full flat form…here are the hybridizers that I patronized in the early days, in order of importance: Jack Carpenter, Brian Millikan, Fran Harding, Dave Talbott, Tom Wilson, Lee Gates, Patrick Stamile, and Pauline Henry.

“The purple line was from CRAYOLA VIOLET (Stamile) crossed with BE MY VALENTINE (Fran Harding).  Some of these seedlings were rust resistant. I still use (some of) those seedlings to maintain rust resistance. (I will have more to say about some of these seedlings later in this article, but for now be sure to note Crayola Violet, as it pollen parent is Super Purple, and the Super Purple family, including many cultivars descended from SP often show up amongst daylilies noted for rust resistance in many surveys and evaluations).

The red line started with DENA MARIE, also a Carpenter, x ROSIE PINKERTON (from Millikan). The yellow line started from Pauline Henry's SILOAM GREEN STRIPE x Tom Wilson's EMERALD SPLENDOR. My white line was primarily a MKM self x some of Brian Millikan's whites.  The oranges are combinations of the red and gold/yellows, and many reds were similar combinations of cool and warm colors.  Mixing my own colors in the burgundy/red/gold/orange range proved to give better results than purchasing a "red" and trying to improve on it. My pinks with red eyes came primarily from Carpenter's PEPPERMINT DELIGHT. THELMA ELAINE AND ANGEL RODGERS from Tom Wilson produced pinks with moderate rust resistance.  Rose-colored blooms came from Fran Harding's WILDERNESS FAT MAMA. I did not purchase any new named cultivars until 2009, when photos of patterned daylilies caught my eye and I invested in some of Carpenter's patterns. I have continued to purchase named cultivars yearly since then, always just for the patterns, and I continue to remove them from the hybridizing program when they show intolerable defects.” 

It is very important to note that Ron points out that not all of the early cultivars used showed rust resistance, nor were all of his diploid seedlings, at the time this work began, highly rust resistant. “My original diploid breeding stock, at the time of the arrival of rust, was not rust resistant (i.e., immune); it was just more resistant than the tets.  I bred the best to the best for generations before I saw plants that could actually stay (completely) rust-free. When I saw that I had a seedling that exceeded the performance of the parent, I removed the parent from the breeding program and continued on with the seedling.” This is important to note, because far too many breeders out there believe that to breed for rust resistance, you must have all cultivars be one-hundred percent rust free, but my experience with breeding for disease resistance suggests that one can start a program with less than 100-percent resistance. In fact, it would be very rare to even be able to begin a program in such a way. Where one should start is with the most resistant cultivars they have or can find and select from there, working to concentrate resistance factors into ever-greater levels of resistance.

Ron working in his seedling bed at peak bloom

At this point, I want to make a distinction between rust resistant and rust immune. A plant that is resistant to rust may show some rust, but will not become completely covered in rust, and the levels of resistance vary from cultivar to cultivar. In my opinion, any cultivar that shows some resistance can be used to breed up higher resistance, so long as it is bred to equally or more resistant cultivars. Immunity, on the other hand, is when a cultivar never gets any rust. While this may be the final goal, not all cultivars that never show rust will have true, genetic immunity, as there is some evidence that some such cultivars may be the result of environmental conditions keeping rust at bay, rather than true, genetic immunity. While it may be advisable to use some seemingly immune cultivars in breeding for rust resistance, especially if they have been consistently immune in various locations or for many years of rust exposure, not all cultivars will truly be immune or pass on immunity to their offspring. So in breeding for rust resistance, the notion that only the immune can be used is inaccurate and Ron’s program points this out.

Now I would like to take a moment to look at Ron’s resistance rating system, to give us a little bit more insight into his process.
I have rated my plants as:
RR (Rust Resistant, or 10) – these never get Rust even under extreme disease pressure.  
HR (High Resistance, or 9) - might get a few pustules on old leaves late in fall.
MR (Moderate Resistance, or 6-7-8) - plants that carried some Rust throughout the season or only in the end of season; this level of Rust didn't hurt overall plant performance or looks. 
PR (Poor Resistance, or 1-6) - plants where Rust started early and took the plant down or damaged it badly.  (I cull Poor Resistance immediately unless they are very unusual.)”
It is important to understand, that in some instances, Ron has used plants from every rating level, but always with a focus toward using one very resistant parent. He feels, and I would tend to agree, that if rust resistance is genetic (as it almost certainly is) and heritable, a plant showing lesser resistance from a resistance-breeding line is possibly carrying resistance factors and can be used should it also offer very unique traits. With that said though, most of his breeding has focused on the RR and HR categories.

So now that we have established some background and the rating levels, let’s look at what Ron has to say about the actual breeding he has pursued in seeking to produce more resistant lines of daylilies. As stated above, once rust first struck, Ron discontinued his efforts at breeding tetraploids and went over to his diploid seedlings to start his breeding efforts over. Those seedlings had been produced prior to the first rust outbreak and showed more resistance than the tetraploids, though very few of them showed high resistance or immunity. Ron was convinced to move forward with those diploid seedlings because, as a group, they showed higher resistance than his tetraploids. Here are some more of Ron’s thoughts on the process of breeding for rust resistance.

We get rust - in the extreme - every year in our garden in Russellville Arkansas. Because of this situation, we changed long ago from hybridizing tetraploids to diploids.  There is absolutely no question that some daylilies have outstanding resistance to rust.  The only true way to control rust is to hybridize new cultivars with the aim of including rust resistance in their genetic makeup.  We have been working to establish rust resistance in our diploid line for over ten years.  We have achieved notable success in producing rust resistant cultivars in a full color range, although some colors are more resistant than others. We started out with a handful, and with rigorous culling, have brought our diploid line up to a 60% RR level.

“I grow from 12,000 - 20,000 seeds per year and I can see the non-resistant seedlings rather fast.  I keep a row of new Southern-bred Tets to get a good strong Rust source, because without a heavy infestation of spores, you really can't make an adequate call on what to cull each season.  I say, bring the Rust on!  Since I needed volume to have any hope of achieving success, I decided to forego tagging crosses as I had in the past, and to make as many crosses and seedlings as fast as possible to create the whole range of colors in Rust-resistant plants. At first I culled all the plants that got Rust in their (seedling) pots. Then I decided to grow all seeds outdoors; it gives a stronger plant and eliminates many would-be rotters.  So now, I collect the seed, stratify it wet in plastic trays, rinse the seed twice a week for 3 weeks, and then plant it out in rows. The seeds generally get planted in late September; two weeks later they are up, which is just in time for fall Rust. In April the seedlings are lined out in blocks 3 x 5 inches apart.

“The previous year's crop is selected and each is given a detailed description on an 8" plastic tag, which is left on until the bloom season is finished.  Then all but the tagged plants are removed, allowing the selections to grow out away from crowding.
By fall they all have new strong growth (as well as) old leaves, which will set the stage for the next evaluation - Rust. Any plants that have (heavy) Rust are culled now, leaving resistant (RR) ones and any that have only light cases of Rust (HR). (I have had to cull some of the most beautiful lilies I have ever seen at this stage.)
The levels of Rust-resistance of the new selections is noted on the flower and plant evaluation tag and only in October are moved into the evaluation block.  Each year I cull, for one reason or another, about 20% of all previous selections in the evaluation block.  Just before the first heavy freeze, all plants in that block are re-evaluated each year and downgraded if necessary.

“The importance of keeping enough Poor Rust (PR) resistant plants to provide adequate infection can't be overstated.

“The year 2008 was the wettest year for us in Arkansas for the past 33 years.  We received 75.45 inches of rain.  It was also the worst year for Rust I have ever seen because of the constant heavy dew.  I had to downgrade some of the 2007 RR (or 10) plants to HR (or 9).  But older plants that I have had for years maintained their resistance code, showing me that there is true resistance, year to year, if properly selected.”

So we can see from this that Ron is following classic selection methods, as any breeder would in selecting for any trait. In selection for resistance, one must expose the individual plants to the problem we are seeking to breed resistance toward, and Ron has done this every year since rust first appeared in his garden by not spraying for rust and allowing it to run through his plants and using it as a culling device. This is a project that anyone who gets rust recurrently in his or her garden can easily pursue, but the desire to do so must be present. Beyond that, I feel there are two more things I wish to point out for this article. The first, which I touched on above, is that you can begin a breeding program for rust resistance by using any cultivars that show above average resistance in your garden. They do not all have to be seemingly immune. The second point is something that Ron states above and that helps me to be convinced that true, heritable resistance to rust really does exist and that he has actually imparted genetic resistance into his lines through selection against susceptibility. Ron states. “But older plants that I have had for years maintained their resistance code, showing me that there is true resistance, year to year, if properly selected.” The importance of this cannot be overstated.

Let us look more closely now at this last point as we close out this article. In any garden that gets rust, there will be some plants that seem immune one year, but are not the next, or in some subsequent years. As noted above, environmental factors can create seeming immunity in some plants. However, such plants, when their immunity is not due to genetic factors, will not produce immune offspring. So how do we determine real immunity or high resistance? It is through replication of results. There are two ways to do this. One is to have many clumps of a given clone growing in many locations, randomly, throughout the infected garden, or in multiple infected gardens. The second is to observe consistent resistance or immunity levels from year to year, over many years, in infected gardens.

So when Ron mentioned seedlings that have been consistently RR in his garden through many years, my interest was peaked and I began to ask many questions about these individuals. While Ron does not have huge numbers of these, there have been a handful of RR and HR seedlings that have consistently scored very high on a yearly basis over many years. I feel that these individuals are very special. Fortunately, Ron recognized their importance, and in many cases is still using them in his breeding as he works toward his eventual goal of large flowered, patterned flowers with very clear colors on vigorous plants with great scapes and branching at about 32” or more in height. While all of these older, proven RR and MR seedlings do not have all of the phenotype points that he desires in his finished line, he has recognized the importance of their long-term rust resistance and so has had the wisdom to keep using them to backcross his subsequent seedlings of more desirable phenotype with. By doing this, he is concentrating their high rust resistance while continuing to select for more refined phenotypes of flowers with improved garden plants. The fact that he has been breeding now for ten years and is only beginning to approach his targeted resistance and phenotype traits for introduction speaks volumes about his commitment to the plants, rather than the desire to quickly produce plants for resale. Such commitment to the plants is admirable.

Ron's seedling bed after end of season culling. This is the same seedling bed in the pictures above!

For anyone interested in Ron’s work, you can see many pictures of his seedlings, complete with some information about each on Ron’s Picasa Web GalleryThere you will find color pictures of many of Ron’s newer seedlings, but a careful review of all the pictures there will reveal some of the older seedlings that have remained RR or HR for many years. Most notable among those are some of the seedlings that go back to 2004 or earlier and have remained RR. Be sure to spend some time finding these seedlings amongst those pictured, as they are very important, both to Ron’s breeding efforts and to demonstrating that long-term resistance is possible.

One of Ron's beautiful lavender seedlings. This is one of my very favorites of his pre-2009 seedlings. To see many of Ron's pre and post-2009 seedlings, be sure to check out his web album, by clicking here or using the provided link in the above paragraph.

In the next installment of this series, we will look at the direction Ron is heading with his breeding, both for resistance and phenotype traits. Ron is a perfectionist, and while I might have introduced some of his RR older bridge plants, he is insistent on achieving his vision of resistance and phenotype combined before he makes any introductions. If only more breeders had this commitment to perfection!

To go to Lessons in Persistence: Part 2 CLICK HERE.