Dependence of leaf area index on different multiplication methods of potato meristem plants grown under field conditions

Using a technology created in EVIKA (Department of Plant Biotechnology of the Estonian Research Institute of Agriculture), disease-free potato meristem plants were multiplied on plastic rolls in peat substrate and the first-generation potato tubers were grown under field conditions. Simple methods of tip-and stem-cutting and plant truncation introduced by EVIKA as well as in vitro micro plant cultivation on plastic rolls were used for field multiplication. The main objective of this paper is to analyse how the leaf area index (LAI) depends on the plant multiplication method, experimental year and variety of the meristem plants. The results for the other methods were compared with the results for the in vitro micro plants. Two local late potato varieties, Ants and Vigri, were used for this study, which was carried out in the EVIKA greenhouse and on an experimental field during 2005-2007. Analysis of the potato meristem plants grown under open-field conditions showed that the multiplication method and experimental year, as well as the variety, had a significant influence on LAI. Leaf area formation of the variety Vigri was more sensitive to unfavourable dry and excessively warm conditions as compared with the variety Ants. In 2005 the maximum LAI (averaged over all the multiplication methods and the two tested varieties) reached 3.4 m(2) m(-2), while in the dry and periodically very hot year 2006 the mean LAI was 2.3 m(2) m(-2) and in the meteorologically nearly optimal year 2007 it was 5.7 m(2) m(-2). Comparison of the multiplication methods showed that all the meristem plants multiplied by the three simple EVIKA methods and grown under field conditions had larger LAI values and crop photosynthetic potentials than did the in vitro micro plants, which were planted on plastic rolls directly from test tubes.