| The symbolization of complementary necrosis genes in
wheat : a proposal J. G. Th. HERMSEN Institute of Agricultural Plant Breeding, Wageningen, Netherlands Heritable remature necrosis in wheat hybrids has been studied by several research workers who all came to the conclusion that necrosis as such is determined by the interaction of complementary genes. The symbols for these genes as used or proposed in the literature are, with the authors' designation of the phenotype, given in the table. The genes are arranged on the basis of their location or probable location in the wheat genomes. A new basic symbol covering all types of complementary necrosis is needed since none of the foregoing symbols is in agreement with the rules for nomenclature and symbolization of genes in wheat as recommended by both the American and the Japanese Committee for Nomenclature and Symbolization of genetic Factors in Wheat : 1. The symbols Le (lethality) and m (probably an abbreviation of macha or of mortality) do not give the chief phenotypic effect (=necrosis) and do not hold true for all cases of necrosis because in many necrotic cross combinations no lethality occurs, neither in F1 nor in F2 and following generations (Hermsen, 1960). 2. The symbol F is only related to the " firing "-type of necrosis which in comparison with other types of necrosis is fairly rate, even though it is genetically related to these types (Hermsen, to be published). 3. The symbols A and B may be confused with the generally used designation of the wheat genomes (Kihara). 4. The use of two symbols for genes determining one character is not recommended by the above mentioned committees. 5. The symbol N proposed by the author in 1959 did not account for the symbol N for nematode reaction proposed by Ausemus et al. (1946). The author proposes to use exclusively the basic symbol Ne (of necrosis) for the following reasons. Necrosis and not lethality is the chief phenotypic effect of the complementary genes . Lethality only occurs in definite hybrids in consequence of necrosis. The symbolization al for albino, Cd for chlorophyll deficiency and D for dwarfism which in given hybrids may also cause lethality, are in close agreement with the symbolization Ne for complementary necrosis. Furthermore the Symbol Ne covers all types of necrosis (progressive necrosis, firing) and also the cases where no lethality occurs. Finally the symbol Ne can cause no confusion with other symbols, as far as the author is aware. There are three necrosis genes (Hermsen 1959, 1960) each located in another wheat genome (Tsunewaki 1960 and unpublished). To distinguish these genes we proposed to add the indices A, B and D to the basic symbol Ne. Of each of these genes some clearly different forms exist, probably multiple alleles (Hermsen 1960 and unpublished). To indicate these different forms we propose to use the indices 1, 2,..., n. Summarizing the proposed symbolization the following series are obtained : NeA1, ..., NeAn; NeB1, ..., NeBn; NeD1,.., NeDn. |