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Physiology and Biochemistry

Influence of Changes in the Nurse Cell System (Syncytium) on Sex Determination and Development of the Cyst Nematode Heterodera schachtii: Total Amounts of Proteins and Amino Acids. F. Grundler, Institut f?r Phytopathologie der Christian-Albrechts-Universit?t Kiel, Hermann-Rodewald-Stra?e 9, D-2300 Kiel 1, Germany; Marlies Betka, and U. Wyss. Institut f?r Phytopathologie der Christian-Albrechts-Universit?t Kiel, Hermann-Rodewald-Stra?e 9, D-2300 Kiel 1, Germany. Phytopathology 81:70-74. Accepted for publication 30 July 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/Phyto-81-70.

The nutrition of seedling roots of Brassica rapa var. silvestris f. campestris ?Stielmus? was manipulated to test whether sex determination in the beet cyst nematode, Heterodera schachtii, is controlled by environmental or genetic factors. Single J2 juveniles were added to germinated roots in water agar drops under aseptic conditions. Half of the test plants were decapitated by removing root tips and shoots. Two days after adding the nematodes, nutrient solution containing minerals and various concentrations of sucrose was poured over the agar drops. Twelve days after inoculation, nematode development in the 10 treatment combinations was examined, and the total amounts of protein and amino acids in the syncytia, adjacent root segments, and uninoculated control roots were determined with sensitive micromethods. Seven treatment combinations supported and three inhibited female development. The experiments provided evidence that under favorable conditions, most juveniles develop as females. In treatments that inhibited juvenile development, the high proportion of juveniles still at the J2 or J3 stage resulted from changes in the nutrient supply. Changes in the total amount of proteins and amino acids in the syncytia, as well as in the control root segments, did not obviously influence female development.