| Classification of tetraploid wheats based on the response
to Aegilops squarrosa cytoplasm Ichiro OHTSUKA Kihara Institute for Biological Research, Yokohama, Japan A total 100 strains of tetraploid wheats were investigated on the genetic compatibility of their genomes to the cytoplasm of Aegilops squarrosa. These tetraploid wheats were classified into three types of responses to squarrosa cytoplasm, as AB, AG and AB' type (Table 1). Genetic analysis proved that two nuclear factors affected by the compatibility to squarrosa cytoplasm. One of them was a factor for plant vigour, which might affect the development or ability of mitochondrion. The other was considered as a factor for the development of plastid. The incompatibility of the latter factor to squarrosa cytoplasm was manifested as follows; gametic sterility in male with lack of starch, zygotic lethality caused by degeneration of endosperm, and chlorophyll variegation in plant due to abnormal development of chloroplast. Majority of Emmer wheats (AABB genomes),Triticum turgidum (3 strains), T. durum (11 strains), T. polonicum (2 strains), T. orientale (2 strains), T. aethiopicum (3 strains), T. isphahanicum, T. dicoccum (17 strains) and T. dicoccoides (4 strains from Palestaine and 5 strains from Zagros Mts. region) showed the zygotic lethality under the cytoplasmic background of Ae. squarrosa. When these strains were crossed to the lines having the genetic constitution of (squarrosa)AABB+1D, many abortive seeds (zygotic lethal) were produced and their genetic constitution was presumed to be (squarrosa)AABB. On the other hand, all F1 seedlings from non-abortive (normal) seeds developed to normal plants in growth with the chromosome number of 2n=29 indicating the genetic constitution of (squarrosa)AABB+1D, although these plants were partialy male sterile due to the gametic sterility of (squarrosa)AB. Genomes of these species were incompatible to squarrosa cytoplasm, and classified as AB type on the basis of their response to squarrosa cytoplasm. Timopheevi wheats (AAGG genomes, 7 strains of T. timopheevi, 6 strains of T. araraticum collected in Trans-Caucasia and 18 strains of T. araraticum collected in Zagros Mts. region) were completely compatible to squarrosa cytoplasm. When the (squarrosa) AABB+1D lines were pollinated with these Timopheevi wheats, no abortive seeds were observed, and all the F1 seedlings developed to normal plants in growth irrespective of their chromosome number such as 2n=28 or 2n=29. These strains were classified as AG type. |
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