| Complying with Hermsen's proposal (1961), the authors designate the necrosis
genes on chromosome V, XIII and XVI with Ne1, Ne2
and Ne3, respectively. The probable genotypes of the four investigated
wheats are shown in Table 2. Performance of the hybrids as to plant height and seed-setting was best in mono-XVI, due to absence of necrosis. Among the necrotic, monosomic F1 plants, however, some difference in the tolerance to necrosis was found, namely, the F1 mono-III performed better as to plant height and, especially, seed-setting, than any other necrotic di- and monosomics. It is reasonable to assume from this result that chromosome III of Chinese Spring carries a gene that conditions severe necrosis. This modifier on chromosome III may or may not be homoeologous of the necrosis gene on chromosome XVI, because those two chromosomes are homoeologous. Growth habit. Monosomic F1 plants for either chromosome IX or XVIII of Chinese Spring had winter growth habit, indicating that those chromosomes of T. macha carry recessive genes controlling winter growth habit. These genes seem to be the same as those found in other hexaploid wheats (Tsunewaki and Jenkins 1959, Morrison 1960). Awnedness. Monosomic F1 plants for chromosome VIII or X were awnletted, whereas all the other hybrids were awnless. This result indicates that T. macha carries hd and b2 On chromosomes VIII and X, respectively. An awn-suppressor of T. macha could not be identified. |
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