Willem Jan de Kogel, Domenico Bosco, Marieke van der Hoek, Chris Mollema
Lit
The effect of different host plants on Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) body size was ...investigated. Thrips from three different populations, from the Netherlands, Italy, and USA, achieved greater body sizes when reared on cucumber than on bean. The same thrips grew larger when reared on susceptible than on resistant cucumber. On the latter, reproduction was reduced, suggesting that smaller thrips have a lower reproduction. However, no evidence was found for a correlation between size and reproduction in experiments with thrips from four different populations, from the Netherlands, New Zealand, France, and USA that differed significantly in body size. Also when individual thrips from the four populations were tested, there was no correlation between size and reproduction. It is concluded that resistant cucumber affects both size and reproduction of F. occidentalis. However, lower reproduction in general is not associated with smaller body size.
Female hybrids of the cross Chironomus t. thummi female × Ch. t. piger male which are largely affected by the sterility inducing Rud syndrome were backcrossed with males of both parental strains. The ...aim of the study was to provide information about those egg volumes that are insufficient for a normal embryogenesis and to ascertain whether in the hybrids the lethally small egg size represents a new abnormal trait of the Rud syndrome. The egg masses obtained contain eggs of very different sizes with volumes ranging from 0.5 nl to 3.49 nl. Embryo mortality is unusually frequent in those eggs of the backcrosses and of the parental strains that have volumes smaller than 1.5 nl. An egg volume of 1.5 nl represents in Ch. thummi the lower limit for those volumes that are sufficient for a normal embryogenesis. Mortality increases with decreasing egg size, reaching 100% in backcross eggs with volumes of 0.99 nl and smaller. Small egg size is a new trait of the Rud syndrome affected thummi female × piger male hybrids. This trait is part of a postzygotic reproductive isolation barrier between thummi and piger and manifests first in the backcrosses. Most backcross eggs show volumes between 1.5 nl and 2.99 nl. Within this volume range the amount of mortality does not depend upon egg volume. Here, embryo death is great in the backcrosses but normal in the parental strains. The high frequency of embryo death in the backcrosses must be predominantly due to the action of the Rud syndrome and a second hybrid syndrome, called HLE syndrome. Since further characteristic traits of these syndromes could be detected in surviving backcross individuals, the study demonstrates the occurrence of the syndromes in this generation also. Therefore, the postzygotic reproductive isolation mechanism of both hybrid syndromes is effective in the hybrids and in their progeny as well.
Klaus Hägele, Monika Kasper-Sonnenberg
4 obrázky, 2 tab.
Lit.
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Z ústavu soukr. ekonomiky při c. k. čes. vys. škole techn. v Praze a ústavu pro zeměděl. účetnictví čes. odboru rady zeměděl. pro král. Čes.
Se 4 grafikony
Ing. Dr. J. ...Schrank ; S úvod. prof. dra Vlad. Brdlíka
Se 4 grafikony
Zvl. otisk Zemědělského archivu
Z ústavu soukr. ekonomiky při c. k. čes. vys. škole techn. v Praze a ústavu pro zeměděl. účetnictví čes. odboru rady zeměděl. pro král. Čes.
