CASTRO, C. M.

PEREIRA, A. da S.

REISSER JUNIOR, C.

ROHR, A.

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virus-based methods are being tested to improve TALENexpression and the efficiency of homologous recombinationin plants. Our goal is to optimize the use of TALENs fortargeted genome editing in potato. In this study, TALENsdesigned to target the ALS (acetolactate synthase) gene wereexpressed in a diploid potato line using a geminivirus-basedsystem and mutations were detected using PCR and sequenc-ing. Co-expression with replicase (REP) was required forefficient virus replication and expression of the GUS reporterin control experiments. These results suggest geminiviruseshave the potential to improve TALEN-mediated genomeediting and enhance the efficiency of homologous recombi-nation in a range of crop species.Dandelion as a Host of Potato Virus Y in Northern MaineBuzza, A, and A AlyokhinSchool of Biology and Ecology, University of Maine, Orono,ME 04469, USA.Potato virus Y (PVY) is an aphid-borne pathogen that causessignificant crop losses throughout the U.S. It is non-persistently transmitted by at least 50 different aphid species,and can infect approximately 120 plant species in at least fivedifferent taxonomic families. Insecticides are not particularlyeffective in preventing its spread because no insecticide killsnon-colonizing aphids quickly enough to prevent their inter-plant movement and probing. Our earlier surveys of vegeta-tion surrounding potato fields in Maine found PVY in severalcommon weed species, including dandelion (Taraxacumofficinale ). Furthermore, infection patterns suggested thatdandelion might serve as an overwintering host. Potentialexistence of a PVY reservoir outside of potato fields is likelyto play a role in the overall dynamics of this disease.CalibrationModel Impacts on Nitrogen Recommendationand Potato ProductivityCambouris, AN1, BJ Zebarth2, N Ziadi1, C Grant3, L-ÉParent41Agriculture & Agri-Food Canada (AAFC) Soils and CropsResearch and Development (R&D) Centre, QC, Canada;2AAFC, Potato Research Centre, NB, Canada;3AAFCBrandon R&D centre, MB, Canada, 4Laval University,Soil & Bioengineering Dep, QC, Canada.Appropriate N fertilization is essential to optimize potato yieldand minimize environmental N losses. This study evaluatedthe effect of rate of fertilizationwith 3 N sources on tuber yieldfor Russet Burbank grown in Quebec. The experimental de-sign included 13 treatments repeated 4 times in each of 5 years.Treatments were 4 N rates (60, 120, 200, and 280 kg N ha−1)for each of 3 N sources [ammonium nitrate (AN), ammoniumsulphate (AS) and a controlled-release N (CRN)] plus anunfertilized control. The CRN was applied 100 % at plantingand the AN and AS were applied 40 % at-planting and 60 %at-hilling. At harvest, total yield (TY) and marketable yield(MY) were evaluated. Two models (quadratic and quadratic-plateau) were used to establish yield N response and theoptimal N rate. TY and MY were significantly influenced byN rate, but not by N source or year. With the quadratic model(r2=48 and MSE=34.7), the N rate to reach maximum TY(39 t ha−1) was 216 kg N ha−1 with a confidence interval (CI)of 200–230 kg N ha−1. With the quadratic-plateau model (r2=50 and MSE=32.6), the N rate to reach maximum TY(37.5 t ha−1) was 153 kg N ha−1 with a CI of 128–180 kg N ha−1. The quadratic-plateau model produced betterstatistical parameters (higher r2 and lower MSE) and an aver-age reduction of N rates of 29 % and a reduction of TY less of4 %. The choice of the model did not influence significantlythe TY but the N rate calculated by the 2 models variedgreatly. In the long-term, this N rate reduction will certainlybe beneficial for the reduction of N loss in the environment.Potato Germplasm Enhancement for Drought Toleranceat Embrapa-BrazilCastro, Caroline M, Carlos Reisser Jr, Arione da S Pereira,and Angela RohrEmbrapa Clima Temperado, Caixa Postal 403, Pelotas-RS,96010-971, Brazil.In Brazil, potato is grown in more than 140,000 ha. Embrapa,the Brazilian corporation for research in agriculture, coordi-nates a national potato breeding program. Given to the climatechange prognosis, research activities aiming to evaluate potatogermplasm for drought tolerance have been under develop-ment since 2006. A polyethyleneglycol-basedmethodology tosimulate water deficit in hydroponic system was established.Experiments have been carried out annually at EmbrapaClima Temperado, Pelotas, RS, Brazil (41°40′42″S, 52°26′22.5″W), in one or two growing seasons per year, i.e. autumn/winter (March-July) and winter/spring (August-December).Potato genotypes have been evaluated for several morpho-agronomical and physiological traits. So far, around 50 geno-types, including old and modern potato varieties as well asadvanced clones, were evaluated. Based on the results, it wasconcluded that potato genotypes respond differently todrought stress. It was also found that the negative effect ofdrought stress in tuber development and yield is more pro-nounced in spring than in autumn season, and that somevarieties recently released by Embrapa have shown goodperformance under drought stress. The genetic mechanismsAm. J. Potato Res. (2014) 91:32–74 41

Potato Germplasm Enhancement for Drought Tolerance at Embrapa-Brazil.

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