Potato late blight control is challenging even in a stable environment. Understanding and, furthermore, predicting how the pathogen will respond to a given set of agronomic and environmental conditions is a key element of successful disease management. It is clear that blight control represents a moving target. Disease incidence and severity and the efficacy of control measures are not easy to predict and depend on several factors. Long and short-term changes in climatic conditions will clearly have a significant impact and chan-ges in active ingredients for chemical control, potato varieties and agronomic practices will similarly influence the disease. Overlying this are changes in the pathogen population that may either be occurring in response to, or independently from, the other factors. Fluxes in P. infestans populations have been described and there is an ever-expanding weight of literature documenting such change. However, until recently much of the population monitoring has been on a local scale and wider comparisons, over longer timescales, with meanngful sample sizes, have been challenging. The EU-funded EUCABLIGHT project has changed this via the assembly of a comprehensive database on almost 17,000 isolates of P. infestans from 21 European countries. A key element of the database is novel SSR fingerprint data that, for the first time, is allowing an objective picture of the pathogen population structure on a European scale. Overviews of the data and more detailed insights into local populations using SSR data will be presented and discussed. | v | ok | Myynti MTT Tietopalvelut 31600 Jokioinen

Organic potato production would be sustainable if varieties planted are adapted to low input and resistant to pests and diseases. Selection of varieties the conventional way limits the variety's performance and chance of selection. When farmers participate in the selection process, lesser time and resources are utilized and faster adoption of new varieties is achieved. 'Participatory research' was used by the project in different locations of the Philippine highlands to: evaluate and select potato varieties for organic production; document farmers' criteria in selecting potato entries and recommend potato varieties for organic production. The basic steps were followed in the participatory process such as identification and orientation of farmers, designing and planning of experiments and monitoring and evaluation, involving six farmers practicing organic production for the last three to five years. The project started with germplasm collection in 2004. A total of 55 potato entries were collected, characterized and multiplied through the rapid multiplication technique. Preliminary evaluation of the 55 entries was done at the BSU organic farm in 2005. During the trial, farmers and researchers selected 15 entries based on yield and resistance to late blight. From Nov 2005 to March 2006, multilocation trials of the 15 selected entries were conducted in different locations with elevations ranging from 1,136-2,350 m asl. Each farmer planted the 15 entries using his/her own practices of producing organic potato. Joint evaluation by the researcher and farmers resulted in the selection of six entries. CIP 13.1.1 significantly produced the highest mean yield (80.51 g/plant) across locations and was selected by all farmers and researchers. The six selected entries were advanced to the promotional trials in November 2006 to February 2007. CIP 380251.17 significantly outyielded the other entries with a mean yield of 147.77 g/plant and a return on cash expense of 80.59 percent across locations. Four entries were finally selected by the farmer-partners and researchers; CIP 380251.17, CIP 13.1.1, CIP 676089 and PHIL 5.19.2.2. These entries have mean yields ranging from 138.10 to 147.77 g/plant and return on cash expense of 52 to 80 percent across locations. The positive return on cash expense suggest that the selected potato entries could be used to promote organic potato entrepreneurship. These entries will finally be recommended for organic production in the highlands. Farmers mentioned desirable traits as their criteria for selection. The primary criterion is agronomic (high yield, late blight resistance and high canopy cover) and secondary are economic characteristics (tuber characteristics that meet market demands such as shape and color). The interaction with the farmers provided valuable information on the varietal characteristics important in organic farming. Farmers learned about on-farm research, thus, enahancing their ability to manage new potato varieties for organic production.

Field trials were conducted to determine potato response to parts per trillion (ppt) per weight concentrations of sulfometuron in soil. The herbicide was applied to achieve targeted, 0-d soil concentrations of 0, 7.5, 15, 30, 60, 120, 240, 480, and 960 ppt. Russet Burbank potatoes were planted immediately after application using standard agronomic practices. Based on midseason visual evaluations, root and tuber injury occurred with 0-d concentrations of only 7.5 ppt. Concentrations at or above 120 ppt caused a significant increase in number of tubers with deformities compared with the control. By the end of the growing season, 0-d concentrations between 120 and 240 ppt resulted in higher percentages of tubers with deformities, such as cracks, knobs, or folds. Using logistic models fit to U.S. No. 1 tuber yield and net return data, doses of 74, 156, and 324 ppt are predicted to result in 5, 10, and 20%% U.S. No. 1 yield reductions, respectively. The model predicted a 20%% net return loss, approximately $$160/ha, occurring at 262 ppt, which is near the 240 ppt concentration determined by standard ANOVAs and means comparisons with single degree of freedom contrasts causing significant tuber quality and yield reductions in our study. Growers using the 240 ppt concentration as an indicator of a no-effect level would encounter actual losses too great to withstand. This modeling approach provides an initial attempt at giving growers the tools necessary for assessing potential losses.Nomenclature: Sulfometuron; potato; Solanum tuberosum L; ‘‘Russet Burbank’’

Avaliou-se seis modelos matemáticos para predizer a dose ótima de nitrogênio (N) para a produção de tubérculos de batata em experimento realizado na UFV, em solo Podzólico Vermelho-Amarelo Câmbico. Foram avaliadas cinco doses de N (0; 50; 100; 200 e 300 kg ha-1) no delineamento experimental em blocos completos casualizados, com quatro repetições. A aplicação do N foi realizada em sulcos, na forma de sulfato de amônio. A cultivar Monalisa foi plantada em 14/05, seguindo-se as normas agronômicas recomendadas para a batata. Os tubérculos foram colhidos e pesados em 14/09. Foram selecionados seis modelos, linear plateau, quadrático plateau, Mitscherlich, sigmoidal, raiz quadrática e quadrático que foram avaliados com base nos critérios: lógica biológica, significância do quadrado médio do resíduo da regressão, não significância do F ou falta de ajustamento, alto valor do coeficiente de determinação (R²), significância dos parâmetros da regressão, ausência de padrão no gráfico de resíduos versus valores previstos e, quando possível a sobra de dinheiro após vender a batata e pagar o adubo nitrogenado. Pelos critérios adotados, o modelo quadrático foi o escolhido e a dose estimada de N para a máxima eficiência econômica foi 163 ou 171 kg ha-1, em cenários desfavorável ou favorável de preço da batata, respectivamente. | Six mathematical models were evaluated to predict nitrogen (N) optimum rate for the potato production in an experiment carried out in a Red Yellow Cambic Podzolic soil. Five N rates (0; 50; 100; 200 and 300 kg ha-1) were evaluated in a completely randomized block design, with four replications. N fertilizer was applied in furrows, as ammonium sulphate. Monalisa cultivar was planted on May 5 following the recommended agronomic practices for the potato. Tubers were harvested and weighed on September 14. Six models, linear plateau, quadratic plateau, Mitscherlich, sigmoidal, square root and quadratic, were selected and evaluated based upon the criteria: biological logic, regression mean square residue, significance of F-test or lack of adjustment, high determination coefficient value (R²), significance of the regression parameters, pattern absence in the graph of residues versus foreseen values and, when possible the money left over after selling the potato and paying the N fertilizer. For the adopted criteria, the quadratic model was chosen and the economic N rate was 163 or 171 kg ha-1, at unfavorable or favorable potato price situations, respectively.

Considerable masses of soil may be lost from arable land during the harvest of crops such as sugar beet, potato and chicory roots, as soil adhering to these crops, soil clods and rock fragments are exported from the field (together with the crop) to places such as headlands, farmsteads and crop-processing factories. This soil erosion process is referred to as soil losses due to crop harvesting (SLCH). These soil losses range from a few to tens of tonnes per hectare and per harvest and are thus the same order of magnitude as soil losses caused by water, wind or tillage erosion. However, only a few studies have incorporated SLCH as a soil erosion process. We investigated the variability of soil losses due to sugar beet harvesting at the field plot scale and the importance of controlling factors related to soil, agronomic practices and crop characteristics. Twenty-six field parcels, distributed over the Belgian sugar beet growing area, were sampled during the harvesting seasons 2002, 2003 and 2004. Soil losses ranged between 1 and 30 Mg ha⁻¹ harvest⁻¹ with an average of 4 Mg ha⁻¹ harvest⁻¹. Gravimetric soil moisture content at harvest was by far the most important controlling factor and was positively and exponentially related to SLCH. Differences in SLCH between harvesting seasons could not be explained by the factors investigated in this study, which indicates that other factors also play a role in SLCH variability.