The expert consultation on the use of crop wild relatives for pre-breeding in potato was a workshop organized by the Global Crop Diversity Trust in collaboration with CIP and took place from the 22nd – 24th of February 2012.

1. Workshop on the use of Crop Wild
Relatives for Pre-Breeding in Potato
Craig Yencho
Department of Horticultural Science
North Carolina State University
Raleigh, NC
CIP
Lima, Peru
Feb. 22-25, 2012

2. Trait Mining in Potato CWR
Janskey-Yencho Pre-breeding Poll
(Jancho Poll – 15 breeders, 3 germplasmspecialists – all US)
1. Which traits should pre-breeding efforts focus on in the
context of climate change?
2. Which CWR taxa are promising but have so far largely
remained unexploited?
3. Where do such taxa occur and what should priorities be for
future collecting?
4. What are the main obstacles for an increased use of CWR in
potato pre-breeding (e.g. taxonomical issues; access regimes
to PGR; funding constraints; etc.) and how can we overcome
them?

3. CWR Utilization in Potato
• Many potato breeding programs have not been heavily involved in using
species in our breeding. Why?
• When we incorporate this material we often take a few steps backwards in many of
the commercial attributes we need in commercial cultivars.
• To me it is like starting up another breeding program which requires additional
funding and I don’t have the funding!!
• CWR takes us on other paths usually not directly in line with cultivar development.
• A program like mine is more oriented to developing finished cultivars, which are
needed now. My clientele and funders want answers now…. not in 20 years
• There are too many genetic barriers to overcome in utilizing these
materials, especially for traditional breeding programs.
• I have reservations about breeding for climate change. Not only will the changes be
hard to predict but associated changes in crop species grown and varieties used will
occur as a natural outcome to changing climate, plus current selection efforts will
already be adaptive in nature to changing conditions. My best guess is to breed for
wider adaptation, resistance to stress, and general hardiness.

4. CWR Utilization in Potato
• More pre-breeding is needed to provide new genetic material on an ongoing basis that can be
incorporated into breeding programs.
• Good examples
• Incorporation of S. andigena materials into northern breeding programs – R to viruses, Late Blight, nematodes, etc.
• Frank Haynes (Deceased) - Long term selection and adaptation research (ca. 20yrs!) S. phureja and S. stenotomum now being used by
Kathy Haynes (USDA-ARS) in 4x-2x crosses – PVX, PVY, processing and nutritional attributes
• Shelley’s recent cold chipper germplasm release (USDA-ARS)
• Chuck Brown’s nematode resistant parental material (USDA-ARS)
• Palta – Frost and cold tolerance in S. commersonnii and S. acaule
• You build it and they will come? In my view, demand for genetically enhance material (via CWR) will
increase as more material becomes available.
• Really exotic materials are exciting, but the more closely related taxa (e.g. diploids in series tuberosa
are a source of rich and interesting traits, which are relatively easy to cross and introduce.
• When germplasm releases are made available it would be useful to simultaneously provide, where
appropriate, markers to assist in tracking the introgression/selection of the material.
• Need to explore enhancing current or new venues to summarize material available through pre-
breeding that can be accessed by breeding programs.
• Allele mining? Is potato a good candidate crop?
• Need to define who and what our targets are…
• Poor vs wealthy, Nutrition vs. Diseases and Pests, Value-added vs Staple-Types?
• $$$ and time… - How much do we have to spend, how will it be targeted and for how long?

5. CWR Utilization in Potato
Chuck Brown (USDA-ARS, Prosser, Washington): Use of closely related wild spp?
• “Very definitely my feelings about uses of wild relatives have strayed afar from the corral of tuber
bearers. I have recently been looking at Solanum sissymbriifolium. This a very spiny non tuber bearing
Solanum. We are looking at it from the standpoint of eradicating Globodera pallida from fields in Idaho. I
have engaged in a recurrent selection program to reduce the spininess and believe that I have made
amazing progress. As I stroll through the greenhouse where I am making pollinations to produced
Reduced Spine Synthetic II, I am taken with the plasticity of this species to genetic change with simple
phenotypic selection. We inoculated this with Meloidogyne chitwoodi, late bight and powdery scab and
Liberibacter. It seemed to be immune to all of these except Liberibacter. Furthermore it has non
pathotype specific resistance to all Globodera spp. If we are looking for a realm of traits expressed in
strong fashion not plague with the special relationships between resistance genes and effectors, this
seems to be the place. What is keeping us from exploring this further? An old technique, really,
protoplast fusion. Just try and find someone who is presently carrying out somatic hybridization. How are
we to access this treasure trove of new genes? Collections. There are only five accessions of S.
sisymbriifolium, one of S. aethiopicum, one of S. quitoense, and on and on. Collection.”
Walter De Jong (Cornell)
• Which CWR taxa are promising but have so far largely remained unexploited?
• “This question assumes that one uses CWR primarily to extract alleles that confer an extreme (but
desirable) phenotype in wild taxa. As Tanksley has shown in tomato and McCouch has shown in rice -
there are lots of invisible beneficial alleles in just about any wild species.”

6. CWR Utilization in Potato
Where do such taxa occur and what should priorities be for future collecting?
We have enough potato germplasm to keep us busy for a long, long time.... The bottlenecks are
characterization and even more so - UTILIZATION! We've barely used what we've got -- why keep
collecting? In addition, it is not like we can't create alleles in the lab if we need to in the future. If you want
to preserve allelic diversity for the future, maybe do it digitally - that is, by doing a lot of sequencing, and
storing the results of what’s "out there in nature" in a database.
What are the main obstacles for an increased use of CWR in potato pre-breeding (e.g. taxonomical issues;
access regimes to PGR; funding constraints; etc.) and how can we overcome them?
• Adaptation! Currently, a breeder expects to spend 20-40 years getting all the garbage alleles out of their
germplasm while you select for the (single) desirable allele you wanted to bring in.
• As time goes by, the gap between adapted and wild germplasm is increasing, making the task of
introgression ever more difficult.
• Who is going to fund a 30-40 year effort nowadays?

7. S. etuberosum (etb) S. tuberosum x berthaultii
• Chilean species • Bolivian origin (ber)
• Non-tuber bearing • Tuber-bearing
• Resistant to • PI 265857
PLRV, PVY, PVX Insect Resistances
• PI 245939 • Colorado Potato Beetle
Insect Resistances • Flea beetle
• Green Peach Aphid • Leaf hopper
• Potato Aphid • Mites
• Leaf hopper • A & B Trichomes

8. S. etuberosum
Tbr x ber
+

9. Somatic Hybrids 1st Generation
(E + TxB)
Etb 6-21-3
A05379-211
4th Generation 2nd Generation

10. • Progeny from etb-ber somatic hybrid
• Green Peach Aphid John Trumble, UC-Riverside
 Reduced fecundity
 Growth inhibition
 Decreased nymph survival
 Novy et al., 2002. AJPR 79:9-18
• Colorado Potato Beetle
 Reduced field defoliation
• Wireworm
 Reduction in tuber damage Juan Alvarez,
 Comparable/better than Mocap DuPont
• Psyllid
 Insect vector of Candidatus Liberibacter psyllaurous (solanacearum)
 Vector resistance could aid in the control of Zebra Chip (ZC) disease
 Confirmed: Butler et al., 2011. Crop Protection 30: 1233-1238

11. PVY Resistance
Transmitted through 2 backcross generations
Resistance lost in 3rd backcross progeny
Genomic Differentiation? E –vs- A
PLRV Resistance
Expressed in 4 backcross generations
Stable across years
Segregation indicates resistance is monogenic
• Reduced PLRV translocation to tuber
Resistance gene Rlretb: Kelley et al. (2009) Mol
Breeding 23:489–500

12. Killing temperature ( C)
Categories Species (example) Before Cold After Cold
Treatment* Treatment**
Group I: Frost tolerant S. acaule - 6.0 - 9.0
and able to cold harden S. commersonni - 4.5 - 11.5
Group II: Frost tolerant S. sanctae-rosae - 5.5 - 5.5
but unable to cold harden S. megistacrolobum - 5.0 - 5.0
Group III: Frost sensitive S. oplocense - 3.0 - 8.0
but able to cold harden S. polytrichon - 3.0 - 6.5
Group IV: Frost sensitive S. tuberosum - 3.0 - 3.0
and unable to cold harden S. cardiophyllum - 2.5 - 2.5
* Plants were grown in a regime of 20°/15°C day/night, 14 h photoperiod.
** Mature Plants were transferred to 2°C day/night, 14 h photoperiod, for 20 days.

13. CWR Utilization in Potato
• CWR’s are very important.
• Efficient and timely utilization of CWR’s is problematic.
• Collection is necessary, but characterization and evaluation may be
more important due to segregation in accessions.
• Sequencing and allele mining should be considered.
• Traits related to climate change are important, but don’t forget
nutritional and disease and pest resistance traits are also key to our
future well-being.
• Long-term funding will always be needed.
• Who’s going to deal with the IP issues?
• Information management and curation and governance of such
• Conservation