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.
Craig Yencho's presentation in the framework of the expert consultation on the use of crop wild relatives for pre-breeding in potato
Workshop on the use of Crop WildRelatives for Pre-Breeding in Potato Craig Yencho Department of Horticultural Science North Carolina State University Raleigh, NC CIP Lima, Peru Feb. 22-25, 2012
Trait Mining in Potato CWRJanskey-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?
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.
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?
CWR Utilization in PotatoChuck 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.”
CWR Utilization in PotatoWhere 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 arecharacterization and even more so - UTILIZATION! Weve barely used what weve got -- why keepcollecting? In addition, it is not like we cant create alleles in the lab if we need to in the future. If you wantto preserve allelic diversity for the future, maybe do it digitally - that is, by doing a lot of sequencing, andstoring 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?
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
• 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
PVY Resistance Transmitted through 2 backcross generations Resistance lost in 3rd backcross progeny Genomic Differentiation? E –vs- APLRV 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
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 - 11.5Group II: Frost tolerant S. sanctae-rosae - 5.5 - 5.5 but unable to cold harden S. megistacrolobum - 5.0 - 5.0Group III: Frost sensitive S. oplocense - 3.0 - 8.0 but able to cold harden S. polytrichon - 3.0 - 6.5Group 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.
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