Thursday, November 28, 2013

Breeding for Rust Resistance in Daylilies: 
Part 3

In this installment we look at realistic goals for our projects. Not everyone can or will have the same goals. What I outline here is my ideas concerning the goals that the entire daylily community might have overall or in the broader sense. However, each person's goals may vary, as their conditions and interest will vary. Some will have more ambitious goals, while others will have less ambitious goals, and that is ok. We can't all have the same goals, as we don't all have an equal situation or interest. There is no one goal that is 'right' while others are 'wrong'. I simply don't work from an 'either/or' proposition, but rather, from a 'both/and' position. It is up to each person to find the point that works for them. For my part, I believe we need a diversity of goals and interests, some working on the plant, others on the flower, some on both. In that way, we can push all the boundaries, and not just one or two. Please know that no matter what you decide you can or cannot do, I support you and appreciate your contribution to the vast and varied world of daylilies! Read on...

Being Realistic About Our Goals

Now that we have our terms defined, let us move on to consider what it means to be realistic about breeding for rust resistance. To begin with, from reading over many years of threads on various message boards and robins and speaking privately with many daylily breeders and growers, as well as general gardeners, master gardeners and landscapers, I see that there have been two equally unrealistic approaches to rust in the daylily world. The first I call the ‘ostrich syndrome’, which has been to ignore it, pretend it isn’t there, isn’t a big deal and won’t impact daylilies, and to either suffer through it and hope others don’t notice, not talk about it and attack anyone who does or just spray and pretend the problem is solved. The second is the opposite extreme, and is the ‘we must breed total resistance right now, at all costs’ approach. Both are too extreme and unrealistic to succeed and neither has succeeded.

On the one hand, rust has continued to spread, invading more and more gardens and moving further north each year and each year since rust appeared the word behind the scene is that daylily sales are diminishing and continue to diminish unabated, at least in the southern states (though clearly, recent economic uncertainty has contributed to this downturn in daylily sales, as has the aging and passing of many of the most committed collectors). On the other hand, many who began attempting to breed for total resistance (immunity) and nothing less have become disillusioned and stopped their pursuit of resistance breeding, either giving up entirely or throwing in the towel and getting in the ‘spray and ignore’ mode, because total resistance didn’t come about instantly. 

I believe that both approaches have been too extreme, ignoring the common middle ground where average breeders, hobbyists, gardeners and landscapers reside. Fear and uncertainty have certainly been a big part of this, but in addition to fear, I see a certain kind of laziness that manifests as a fear of the effort, as well as a lack of good information on realistically breeding for disease resistance that has caused a lot of uncertainty and only contributed to this situation.

There is much good information on breeding for disease resistance if one looks outside the daylily world. Many plant species have devoted breeders, professional/commercial breeders and/or hobby breeders, who have pursued various types of resistance in the breeding programs they have undertaken. Some have not succeeded, but many have succeeded well and should be studied and emulated. One of the most important things we can do is to get realistic about what our aims should be.

It should be obvious that I do not advocate a ‘total resistance’ or ‘absolute immunity’ approach, because I think this is highly unrealistic. The notion that we are only going to introduce plants that show immunity forgets that there is more than one strain of rust and rust will continue to mutate. In short, my aim would be to begin to focus on the production of plants showing good to high resistance through combining multiple genes for resistance, or conversely to make the removal of highly susceptible individuals a major goal of breeding, thus beginning to eliminate the introduction of more and more new rust magnets. Perhaps the most astonishing thing to me is that so many highly susceptible plants have been continually introduced since rust first reared its orange-speckled head in 2000. In my opinion, this reflects poorly on the daylily community (and is something I have heard echoed from daylily growers, master gardeners, home gardeners and landscapers alike, repeatedly).

So in practical terms, what am I actually suggesting the hobbyist do? Well, first of all, except for those few plants that show low tolerance or in those few areas of the country where rust is a continuous presence (and sometimes lethal problem), having some rust is not a great tragedy, especially where many of the plants you grow show good to high resistance and there is some effort made to reduce the presence of the least tolerant and/or most susceptible, so that the garden is still attractive and does not look like a disaster area.

It goes without saying that the first time rust shows up in your garden, you are in for a shock, because many things you grow may be highly susceptible. Sentimental favorites and expensive new introductions can quickly become hideous rust-fountains and may even show poor tolerance and be adversely effected for a whole growing season or more, but once the initial shock wears off, you can take a deep breath and start to note those that show minimal rust or even no rust. Then you can begin to research and communicate with others concerning cultivars that show good to high resistance or immunity. As you eliminate the most susceptible (or those with low tolerance are eliminated for you), you can then begin to divide and increase plantings of you own resistant plants and add new cultivars that show some resistance or immunity for other gardeners, knowing that results may be slightly variable in your garden, depending on the environment and the particular strain of rust you have as opposed to those that others have experienced.

It is a wise thing during this phase to focus on less expensive cultivars with a long track record of exposure to rust. Not buying large numbers of new introductions, unless some data about their rust resistance is available, would also be a wise approach. Or if you simply can’t part with some sentimental favorite or new expensive introduction or must have something that is unknown, spraying may be a viable option for you and information about sprays is readily available online.

Do note though that spraying is expensive and only masks the problem, so I do not feel it is actually a viable approach for breeders, but at least you won’t see rust. If you are selling plants, it will probably be necessary for you to spray, but that does not mean you have to spray year round. If you spray in spring, but then stop spraying in late summer, you can still rate cultivars and especially any seedlings you may raise for their rust response. I personally consider this the most responsible spraying regimen for sellers, as it allows some awareness and culling for rust susceptibility. It must be noted though, that no one who is spraying in order to sell is actually verifiably ‘rust free’, because spraying does not kill rust in the plant, but only suppresses the sporation, thus any plant purchased from a ‘rust free garden with a spraying program’ can sporate once they are in their new home and no spray is being applied, if there was any exposure in that sell-garden in the past. This happens frequently and is one of the major ways that rust is spread. Spraying is only a prophylactic, not a cure!

So once you are past the initial shock of your first rust outbreak, and all the heartbreak has ensued, tears have been shed, curses have been uttered and hair has been pulled, you may begin to find that once the most susceptible are gone, rust is not too unbearable in a garden setting. This has been my experience and has helped me to see the middle ground approach I am advocating here. A garden full of rust-fountains is traumatic, but a garden full of plants with some slight amount of rust and some plants with no rust at all is quite manageable and not too terribly noticeable. 

I manage a garden where this is the approach we have taken and now our annual fall outbreak is barely even noticeable unless you go out and start actively looking on the undersides of the leaves. So how was this accomplished? By removing the highly susceptible altogether and only keeping or adding those with high resistance and/or immunity, most notably by dividing those of that nature in the garden and increasing the plantings of those cultivars and by then judiciously and slowly adding new cultivars that have been shown to have some resistance and then removing any of those that failed and increasing those that have shown suitable resistance in that garden. 

I consider this approach to simply be an aspect of garden maintenance and building. With experience, you too will come to realize that not everything you plant succeeds and some things fail and must be redone, replanted, rethought. This is life in the real world. However, this garden is not a breeding garden and in such I would take a different approach, but I think the approach I have taken in this garden is a realistic approach for the average gardener.

The major difference in a breeding garden would be that I would leave a good number of the most rust susceptible in order to be sure the seedlings and potential breeders were sufficiently exposed to rust to confirm their resistance levels. The cultivars that I would personally tend to keep to ensure proper rust exposure also would tend to be those I would be most interested in using for ‘salvage projects’, so such cultivars in my hybridizing garden serve two purposes – to infect the future generations and to preserve a special trait for later blending into resistant lines.

Since a small amount of rust in a garden is neither unsightly nor deeply traumatizing (to the gardener or the plants) and since the goal of breeding for total immunity is highly unrealistic for the average breeder, I tend to find that breeding for good to high resistance is the most realistic approach, with immunity both welcome and sought after, but not the only goal of the breeder. To make full immunity the sole goal of a breeding project is to invite failure and disillusionment, both of which usually lead to giving up, but when the focus is both plants with usable resistance and the removal (or non-introduction) of those with high susceptibility, we can see progress and be encouraged enough to continue our work. This is a realistic goal that is achievable and will lead to plants that can be useful and valuable to gardeners, landscapers, breeders and collectors. Further, it serves the purpose of eliminating new rust magnets, which are so disheartening and angering to so many, now that rust is simply a reality of growing daylilies.

The old rust magnets from the pre-rust days may be excusable because they were introduced before rust appeared, but the same cannot be said for those introductions made since rust appeared, especially those from recent years. I would strongly encourage the identification of resistant cultivars and the introduction of new cultivars showing resistance to help the daylily maintain its place amongst the gardens of the world and not continue to slide further and further out of favor. For the average gardener, plants showing acceptable resistance are going to become more and more important if they are to continue to grow daylilies.

I would stress that I do not advocate a rush to compost every rust magnet, or highly susceptible cultivar. There are reasons for this. The first and foremost is that one of those that is highly susceptible to a current form of rust may have resistance to a new form of rust that may emerge, or there may be other important genes there. I do think that identifying those with high susceptibility is important both to allow gardeners to avoid them and to allow those who wish to maintain them to know what they are getting into. In that vein, I do encourage that those who are going to spray anyhow to maintain as many of these as they can, just to keep the gene pool present, but I would encourage them to note their susceptibility to prospective buyers and perhaps use them with great care in breeding projects, possibly only in a salvage project wherein the offspring will be exposed to rust and culled for susceptibility.

I do not advocate the destruction of huge swaths of the domestic daylily gene pool, and I do not think a breeder should rush in and destroy all their seedlings from a given cultivar, just because it is highly susceptible. Rather, watch those seedlings carefully and look for any improvement in resistance over the susceptible parent and use them to continue the salvage project. A salvage project of this nature can take generations to achieve, after all. 

There will be a difference in what is maintained by a collector who is spraying their garden, by a breeder who is responsibly trying to continue improving the entire daylily and the average gardener or landscaper who wishes to grow daylilies. The first of these may wish to spray, the second may even spray for part of the year, but the last two aren’t likely going to spray and until we acknowledge this fact and begin to think of their interests, we condemn our beloved plant to a future of obscurity and infamy amongst such people, especially in warmer areas. Ask yourself this – How many average gardeners or landscapers use tea roses?

Now some may come along and say, “But what will you do when a new strain of rust comes your way? Then all your work will be for nothing!” Well, not necessarily. To begin with, we do not know how much variation of effect there may be in the various strains of rust. Secondly, we do not know how much variability of response there may already be in resistance genes in the current daylily gene pool, and just as new strains of daylily rust will appear, so too will new mutations for resistance appear (or be recognized as already present) in the daylily. This is a genetic dance after all between pathogen and host. 

Further, my personal approach to various strains of rust will be to simply note how a given cultivar showing high resistance over many years responds to a new strain that it has susceptibility to and then to cross it to a cultivar that shows good resistance to that strain. Thereby I can combine genes for resistance to various strains of rust. In other words, as rust continues to mutate, my work continues, so there is never a point at which one is ‘done’ and has developed ‘proven lines of daylilies that can never get rust’. In reality, there is no such thing, so rust resistance becomes just another trait that the breeder is observing, recording information about and selecting for, just as any other trait such as branching, foliage type, sun-fastness, water resistance of flowers (non-water-spotting), etc. In the end, time and time again, we see that most breeders can walk and chew gum at the same time…I believe selection for rust resistance is just another aspect of selection and nothing more.

To end this section, let us reiterate the practical methods of dealing with rust for various settings.

1. For average gardeners and landscapers, identification and use of good to highly resistant or immune cultivars is paramount, as is removal of highly susceptible cultivars and replacement with another species or another cultivar of daylily known to show resistance or immunity. In this way, the garden is kept attractive and expensive spraying programs are avoided. Production of resistant, garden-worthy daylily cultivars then becomes paramount for breeders, as well as education and identification of resistant cultivars amongst collectors and sellers, in order to maintain the interest in daylilies of this segment of the gardening population.

2. Collectors and sellers use a spraying program if desired or legally required, at least through their sell/display season. They maintain both resistant and no-resistant stocks, but make some effort to know which is which, at least marginally. No more ‘ostrich syndrome’ as if it is irrelevant or they can’t be bothered with such trivialities. Become part of the solution, rather than part of the problem. Sellers should be able to advise prospective clients on those cultivars showing some resistance to attempt to ensure happy customers and to not further damage the reputation of the daylily in the eyes of people becoming increasingly wary.

3. Breeders begin to identify cultivars showing good to high resistance and/or immunity and use those cultivars. Breeders maintain a suitable number of susceptible individuals to assure rust infection of their seedlings and where they must use their highly susceptible cultivars and seedlings in their breeding work, make them part of a salvage program to bring desired traits onto a resistant plant by crossing them to known resistant and/or immune plants. The goal of the breeder is not to create total immunity, but acceptable resistance, with the presence of occasional immune individuals as an added bonus, while also eliminating (and not introducing) the highly susceptible. Breeders seek out, identify and use resistant cultivars and expose (at least) their seedlings to rust in order to eliminate the most susceptible. 

Elimination of the most susceptible individuals becomes the most important aspect of breeding programs. The more of these that can be eliminated as future breeders or introductions, the better it is for the potential resistance of your overall gene pool. In other words, exposing your seedlings and eliminating the highly susceptible becomes the most important aspect of breeding for resistance along with using cultivars and seedlings that have shown consistent resistance over a long period of time and in multiple locations. We will look at these points in much greater detail when we discuss breeding strategies.

For our next installment, we will consider the importance of identifying consistently resistant cultivars...