| Fertility and chromosome transmission of synthetic
pentaploids involving D,M, or Mu genomes of Aegilops Tetsuo SASAKUMA and S.S. MAAN Kihara Inst. for Biol. Res., Minami-ku, Yokohama, Japan, and Agronomy Dept., North Dakota State Univ., Fargo, ND, USA The concept of genome analysis was introduced by the investigation on AABBD pentaploid plants by KIHARA (1924), and his pioneer works resulted in the identification of twelve basic genomes in Triticum and Aegilops. Among them, the genomic similarity of analogy was reported among the D of Ae. squarrosa, M of Ae. comosa, and Mu of Ae. uniaristata (KIHARA, 1949). The authors have been studing on the cytogenetics of the synthetic amphiploids between T. durum (AABB) and Aegilops species having D, M and Mu genomes (MAAN and SASAKUMA, 1978). The present paper reports the fertility and chromosome transmission of synthetic pentaploids having AABB genome in common and D, M, or Mu genomes. Materials and Methods Ae. squarrosa var. stragulata (DD), Ae. comosa (MM), and Ae. uniaristata (MuMu) were crossed with T. durum Sel. 56-1 (AABB). (Aegilops species used in the experiment were originally supplyed by Dr. B. L. JOHNSON, USA). The F1 plants were treated with 0.01 % colchicine to obtain amphiploids of AABBDD, AABBMM, and AABBMuMu, where the AABB genome was genetically identical. The plants with 42 chromosomes and stable pairing conformation were selected from the F4 progenies of the respective amphiploid, and the reciprocal crosses were conducted among the amphiploids, T. aestivum cf Chris (AABBDD), and T. durum Sel. 56-1. Pollen fertility (% of stainable mature pollen grains) and selfed seed-set (% of seed-set in 1st and 2nd florets) were examined in each pentaploid obtained. Also, the respective pentaploid plants were backcrossed reciprocally with T. durum Sel. 56-1, and the cross-seed production and the somatic chromosome number of BC1F1 plants were examined. Results and Discussion The crossability in the reciprocal crosses among T. durum, T. aestivum and the three synthetic amphiploids were summerized in Table 1. The cross-incompatibility was found in the case of AABBMuMu (female) x AABBMM (male), where the reciprocal cross was successful. The slow or inhibitory pollen tube germination of ABM pollens were observed on the stigma of AABBMuMu plant. The similar phenomena to the present observation were observed in the cross between a cytoplasmic substitution Chris having the cytoplasm of Ae. uniaristata (female) and AABBMM amphiploid (male). Since the cytoplasm of AABBMuMu amphiploid came from Mu-donor species, the cross-incompatibility in the cross of AABBMuMu(female) x AABBMM (male) may be due to the incompatible interaction between the cytoplasm of Ae.uniaristata and M genome. Also, the cross-inviability was noticed when T. durum was used as the female parents in the crosses with the two amphiploids involving M and Mu genomes. All seeds obtained in these crosses were shrivelled with undeveloped embryos, and did not germinate in petri-dishes. This cross-inviability was reported to be due to the dosage unbalance between the endosperm and embryo genome constitutions, responsible for 5D chromosome of a common wheat to restore the viability (SASAKUMA and MAAN, 1978). |
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