Plant resistance to Myzus persicae induced by a plant regulator and measured by aphid relative growth rate

Myzus persicae showed a reduced relative growth rate on plants given soil drenches of 1% CCC (a plant growth retardant), and a greater reduction when CCC was applied as a foliar spray. The use of the relative growth rate of aphids as a convenient measure of their performance in relation to plant resistance is discussed.

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Zusammenfassung Die Resistenz von Kohlpflanzen, die mit 1% CCC (einem Regulator des Pflanzenwachstums) behandelt worden waren, gegen Myzus persicae wurde mit Hilfe des Wachstumsquotienten der Blattläuse (g/g/Tag) gemessen. Diese Methode arbeitet rasch und ergibt eine ziemlich geringe Variabilität. Der Maßstab scheint sinnvoll und ziemlich empfindlich zu sein.Mit CCC gedüngte Pflanzen zeigten stets eine ziemlich starke Verminderung des Wachstumsquotienten von Myzus persicae. Wurde CCC auf die Pflanzen aufgesprüht, so ergab sich ein noch geringerer Wachstumsquotient der Blattläuse.

     

Chromosome number and ploidy-level in a Dutch population ofCrenobia alpina Dana (Planaria)

A Dutch population ofCrenobia alpina was found to have a chromosome number of 2n=42. One pair of large chromosomes is acrocentric and probably shows a secondary constriction; one small pair is acrocentric as well. All other chromosomes are metacentric or sub-metacentric; it has not been possible to discriminate with certainty between them. According to the hypothesis ofDahm (1958) populations with, 2n=42 are autohexaploid, the basic genome consisting of seven chromosomes. On basis of the karyotype it was concluded that the Dutch population described here, is not autohexaploid but functionally diploid, perhaps allohexaploid.