Summary
Seven of the wheat crosses which were performed in 1954 and 1955 produced a uniform semi-lethal F1. Among these were four combinations with the spring wheat Koga and two with the Turkish winter wheat Eskischir. The degree of withering in the F1 appeared to be dependent on the variety with which Koga or Eskischir were combined. In the F2 of the Koga crosses carried out in 1954 a 9 : 7 ratio of semi-lethals and normal plants was found. The almost continuous gradation in semi-lethality within the group of semi-lethal plants of every F2 was conspicuous.
The facts are explained as follows: Two complementary genes determine the semi-lethality as such, while “modifying genes” are responsible for the different degrees of semi-lethality of the different F1's and for the variation in degree of semi-lethality within every F2. In the discussion this explanation is given in detail.
It is pointed out that it is perhaps possible, with the aid of the phenomenon of semi-lethality, to discover or confirm relationships between species and/or varieties.
Finally it is suggested that the rejection of F1's with withering symptoms is premature.
Samenvatting
Zeven van de door ons in 1954 en 1955 verrichte tarwekruisingen leverden een uniforme semi-lethale F1. Hierbij waren vier combinaties met het zomertarweras Koga en twee met het Turkse wintertarweras Eskischir. De graad van verdorring in de F1 bleek afhankelijk van het ras, waarmee Koga resp. Eskischir werden gecombineerd. Bij de in 1954 verrichte Koga-kruisingen werd in de F2 een 9:7 verhouding van semi-lethale en normale planten gevonden. Opvallend was de bijna continue gradatie in semi-lethaliteit binnen de groep der semi-lethale planten van elke F2.
Deze feiten worden als volgt verklaard: Twee complementaire factoren bepalen de semi-lethaliteit als zodanig, terwijl “modifying genes” verantwoordelijk zijn voor de verschillende graden van semi-lethaliteit van de verschillende F1's en voor de variatie in graad van semi-lethaliteit binnen elke F2.
Vervolgens wordt de aandacht gevestigd op de mogelijkheid om met behulp van het verschijnsel der semi-lethaliteit, verwantschap tussen species en/of rassen te ontdekken of te bevestigen.
Tenslotte wordt het verwijderen van de F1's met de besproken afstervings- of verdorringsverschijnselen voorbarig genoemd.
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Hermsen, J.G.T. Semi-lethality in hybrid offspring of wheat. Euphytica 6, 18–25 (1957). https://doi.org/10.1007/BF00179513
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DOI: https://doi.org/10.1007/BF00179513