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Genotypic reaction of sugar beet to Rhizoctonia solani root and crown rot - susceptibility, yield and quality at different intensity level of infestation

  • Autor/in: Buddemeyer, J., B. Märländer
  • Jahr: 2005
  • Zeitschrift: Z.PflKrankh. PflSchutz 112
  • Seite/n: 105-117

Abstract

Sugar beet (Beta vulgaris L.) root and crown rot caused by Rhizoctonia solani is becoming increasingly important in Europe. A concept for integrated control of the disease is based predominantly on the cultivation of sugar beet varieties with tolerance to R. solani. This investigation aims to determine the influence of infestation on disease symptoms, yield and quality parameters, and the relationship between the level of Rhizoctonia root rot and the yield loss of a susceptible and a tolerant sugar beet variety, respectively. Natural infestation as well as additional inoculation were used at two sites (Lower Saxony, Bavaria) in 2002 and 2003 to obtain different intensities of infestation. The degree of resistance was expressed by the Rhizoctonia index (RI) of 1 (plants healthy) to 9 (plants dead), and the tolerance by the response of white sugar yield to the disease, which was similar for both varieties. However, infestation led to a significantly lower disease severity of the tolerant variety. Without infestation, white sugar yield was 14 % higher for the susceptible variety, while it tended to be similar at RI of 2 to 3 and decreased to about 0 at RI of 9 for both varieties. The reaction of white sugar yield was mainly influenced by the reaction of root yield in response to different RI levels, while sugar content decreased and standard molasses loss increased only to a smaller extent. R. solani infestation led to an enormous increase of reducing sugars for both varieties, which was up to eleven fold higher for the susceptible variety. The molassigenic components sodium and amino-N showed minimal or no reaction to infestation, whereas potassium increased with increasing disease severity. Quadratic regression was uniformly used to describe the relation between Rhizoctonia root rot and yield and quality parameters as well as for reducing sugars. Instead, an optimal fitting of curves for the parameters white sugar yield and reducing sugars was achieved using a rational and linear function, respectively. The occurrence of the disease, the degree of infestation and damage are not predictable. Consequently, breeders are challenged to provide new varieties with both traits, a high degree of resistance and high yield performance under no infestation conditions.
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