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Bakinowska E.,University of Life Sciences in Poznan | Pilarczyk W.,University of Life Sciences in Poznan | Pilarczyk W.,The Research Center for Cultivar Testing | Zawieja B.,University of Life Sciences in Poznan
Acta Agriculturae Scandinavica Section B: Soil and Plant Science | Year: 2015

In the years 2002–2005, special trials concerning the level of infection of pea varieties by downy mildew were performed in Poland. In these trials, the large number of varieties were tested in many locations (environments), separately on reach and light soils. Obtained trial data are unique because of the large scale of the performed investigations and also for the fact that all the observations were made by the same observer. In a paper, two methods of statistical analysis of such (ordered) data are compared. Several models have been proposed for the statistical interpretation of ordinal data. One of the most popular is the cumulative-type fixed logistic model. In the present work, using two field pea data sets, we considered whether adding random effects to the simple logistic model can improve inference. It was investigated whether there is any difference between the decisions concerning varieties resulting from the simple logistic model and the proposed mixed logistic model. The two models were also compared in terms of goodness of fit. According to two applied goodness-of-fit statistics, the mixed model performed better in all the cases. Statistical analysis (what is important for practical agriculture) enabled identification of the most resistant and the most susceptible variety from the analyzed set of cultivars. © 2015 Taylor & Francis

Przystalski M.,The Research Center for Cultivar Testing | Tokarski P.,The Research Center for Cultivar Testing | Pilarczyk W.,The Research Center for Cultivar Testing | Pilarczyk W.,University of Life Sciences in Poznan
Field Crops Research | Year: 2013

Oat crown rust is a fungal disease caused by pathogen Puccinia coronata f. sp. avenae. Crown rust reduces oat yield and causes thin kernels with low weight. In Polish trials on spring oat one of the compulsory observed characteristics is resistance to oat crown rust. In the present work, the generalized linear mixed model with several variance components is applied to model the resistance to oat crown rust in series of oat trials. The answer to the question which oat varieties tested in two consecutive years 2009 and 2010 in Polish post registration trial system are the best in terms of resistance to crown rust was searched for. © 2013 Elsevier B.V.

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