Einfluß von sortenspezifischen Merkmalen, unterschiedlichem Stickstoffangebot und Kupfer auf die Ertragswirksamkeit von Phytophthora infestans in Kartoffeln

Three potato varieties – Nicola, Rosella, and Simone, differing in the time of initiation of tuber formation (early, middle, late, respectively) – were grown in a 3-factorial field trial for two years in 2 rotational positions i. e. after grass clover and winter wheat in order to induce a different fertility status. A copper control was included. Nitrogen supply after grass clover was between 26 to 32 kg higher than after winter wheat. Late blight severity was high in 2002 but almost nil in 2003 (Area under the curve 1100 versus 75, respectively). In both years, it was consistently but not significantly higher after grass clover. N-mineralisation rates in 2002 were below average due to unfavourable weather conditions in May and June. Thus, only in 2003 the additional N-supply after grass-clover was translated into significant yield increases. Although Simone was most resistant it did not yield more then Nicola while Rosella significantly outyielded the other two varieties in both years. While copper treatment had a moderate but significant impact on disease severity in both years, yield increases due to copper were only 1 and 5% in 2002 and 2003, respectively. It is concluded that the combination of the fertility status of the site and varietal choice is an important system based means of reducing yield losses due to late blight in organic potato production while the use of copper fungicides may not result in the desired yield effects

Effekte veredelter Rohmaterialien angewandt als Dünger oder Wachstumsstimulatoren auf Pflanzenwachstum und -gesundheit

In an EU CRAFT project (COOP-CT-2004-508458) running from March 2004 to March 2006, an international consortium of producers of environmentally benign crop inputs, RTD performers and end users, evaluated the production and use of products manu-factured from different raw materials such as seaweeds, pine needles, trees and herbaceous species or physically hydrolysed bovine fur and hair residues. At the field level, the products were applied as solid pellets or liquids, as fertilisers or sprays, respectively. This paper presents as an example results from field trials of organically grown potatoes and tomatoes at the University of Kassel. Assessments were per-formed on yield, plant health and quality aspects. In most of the experiments solid products (pellets) with nitrogen contents between 7 to 12% resulted in comparable growth effects as obtained with hornmeal fertilisers. However, one of the liquid prod-ucts applied as a spray in potatoes increased yield significantly. A combination of the same liquid and a solid product based on plant raw materials reduced plant and fruit late blight in a field trial with open-field tomatoes. It is concluded that especially the combination of well adapted liquid and solid products can have promising effects on crop performance

Resistenzinduktion bei Tomaten gegen Phytophthora infestans durch Biodüngemittel und Pflanzenstärkungsmittel

Three biofertilizers (BF) and three plant strengtheners (PS) were tested in comparison to chemical fertilizer application and BABA (DL-3-amino-n-butanoic acid), respectively for their effects on the reactions of six different tomato varieties against three isolates of Phytophthora infestans in detached leaf disk assays. All experiments were repeated twice with six replicates each. Two of the BF (BioIlsa and Biofeed Quality) significantly reduced late blight severity as compared to horn meal and chemical fertilizer with no fertilizer by isolate and fertilizer by variety interactions. All PS significantly reduced susceptibility of all tomato varieties. However, the interactions among PS, variety and isolates were highly significant suggesting that different resistance mechanisms might be affected by the PS and BABA. Preliminary results indicate that the combined effects of PS and BF are additive without interactions

Kontrolle von Rhizoctonia solani in Kartoffeln mit einer neu entwickelten Reihenapplikationstechnik von suppressiven Komposten

The soil borne pathogen Rhizoctonia solani is of increasing importance since organic seed potatoes are compulsory in organic potato production. No convincing measure to control the disease is available for organic production. The effect of a suppressive compost mixture of organic household and yard waste to control R. solani in potatoes was tested in an organic field trial at the University Kassel in 2006. The compost was directly applied at the seed tuber area. Seed tubers (variety Nicola) naturally infested with black scurf were planted in three infection classes (no, middle and high infection). Compost amendment had a strong impact on symptoms of R. solani on tubers. The reduction of both the infestation of harvested potatoes with black scurf and the rate of tubers with deformations and dry core was significant at final harvest. Although the rate of initial infection of the seed tubers had an impact on tuber health and quality the disease was reduced up to 50% in all infection classes. These promising results en-courage increasing the research on a development of a strip application technique of composts to control the disease

Einfluss von ligninhaltigen Komposten und Pflanzgutgesundheit auf den Befall mit Rhizoctonia solani bei Kartoffeln

The effects of initial seed potato infection and suppressive composts made of mixtures of organic household and yard waste on the R. solani severity in potatoes were tested in field trials under organic conditions at the University Kassel in the years 2006-08 and at two sites in northern Germany in 2008. Composts directly applied in strips to the seed tuber area at 5 t dry matter ha-1 significantly reduced both the infestation of harvested potatoes with black scurf and the percentage of tubers with malformations and dry core The rate of initial seed tubers infection and the site significantly affected tuber health and quality

A review of varietal change in roots, tubers and bananas: consumer preferences and other drivers of adoption and implications for breeding

This review of the literature on varietal change in sub-Saharan Africa looks in detail at adoption of new varieties of bananas in Uganda, cassava in Nigeria, potato in Kenya, sweetpotato in Uganda and yams in C^ote d'Ivoire. The review explored three hypotheses about drivers of varietal change. There was a strong confirmation for the hypothesis that insufficient priority given to consumer-preferred traits by breeding programmes contributes to the limited uptake of modern varieties (MVs) and low varietal turnover. Lack of evidence meant the second hypothesis of insufficient attention to understanding and responding to gender differences in consumer preferences for quality and post-harvest traits was unresolved. The evidence on the third hypothesis about the informal seed system contributing to slow uptake of MVs was mixed. In some cases, the informal system has contributed to rapid uptake of MVs, but often it appears to be a barrier with inconsistent varietal naming a major challenge