The Viariation Of Rye Chromosomes In Primary Octoploid Triticale

Common wheat (Triticum aestivum L., AABBDD,2n=6x=42) is one of the most important food crop in the world for approximately one-third of the world population. In modern agriculture system, owning to backbone parents of wheat are used more frequently and intensive production, the genetic basis of wheat become increasingly narrow and its genetic diversity become declining, the resistance to biotic/abiotic stresses of wheat losing gradually, all of these restrict the yield and quality improving in wheat. To resolve the problem, researchers focused their eyes on wild relatives of wheat, which possessing abundant genetic variations. It is the advantages to transfer the desirable genes into wheat, and it can broaden the genetic background of wheat as well as improve the yield and quality. Rye (Secale cereale L.) is the third genetic source for wheat improvement and it has provided a number of desirable genes, such as those for resistance to biotic and abiotic stresses and associated with increased yield potential, for use in wheat breeding.In the present paper, a primary 8x triticale (MQ) between common wheat variety ’Mianyang 26’(MY26) and Qingling rye through wild cross and chromosome doubling of hybrid F1 plant was obtained. The chromosome behaviors of MQ were investigated at metaphase I, anaphase I and tetrad period in meiosis of pollen mother cell. The selfing fertilities and hybridization fertility were analysesed for both second selfing generations of MQ and hybrid F1 of second generation of MQ with MY26. The plants with highest, moderate and lowest seed setting ratio for selfing and hybridization, respectively, were selected to analysis rye chromosome constitutions by in-situ hybridization (ISH) and FISH. The main results are described as follows:1. Abnormal behaviors of chromosome in primary octoploid triticale pollen mother cell during meiosis was observed. (1) At metaphase I, there were a lot of univalents which derived from rye and wheat, and a few of multivalents were also observed. (2) At anaphase I, there were many lagged chromosomes that 66.76% derived from rye. (3) There were micronuclei with different size and numbers that 88.43% derived from rye in the tetrad stage. The results provide a certain basis for cytological instability in primary octoploid triticale.2. Unbalanced segregations of chromosomes between wheat and rye in selfing progeny and hybrid F1 of primary octoploid triticale were found. The somatic cells with different chromosome constitution or number in a same plant were observed in some selfing progenies of MQ and hybrids between the second generation of MQ, rye chromosomes in pairs which not separated were observed in hybrids, these results suggested that unbanlanced segregation of chromosomes were existed in somatic cell and sexual cell. This phenomenon was reported rarely before.3. The transmission rate of rye chromosome through gametes in primary octoploid triticale was analysised. The highest transmission rate of rye chromosome was 4R, and that of the lowest was 5R through female gametes; whliethe highest transmission rate was 5R, and that of the lowest was 4R through male gametes; meanwhile, the transmission rate of rye chromosome through male gametes was higher than that through female gametes except 2R and 4R. The results provide a certain basis for transmission rate of rye chromosome through gametes.4. Variations in rye chromosome number in selfing progeny and hybrid Fi of primary octoploid triticale were analysised. Different rye chromosomes appeared in different frequence, in the third generation of MQ,7R being the most frequent,4R,5R, the second and the third,6R, the least; in F1 between the second generation of MQ and MY26,4R being the most frequent, 2R, the second,5R, the least. The results provide a certain basis for transmission rate of rye chromosome in wheat.5. Stucture variations of rye chromosomes in selfing progeny and hybrid F1 of primary octoploid triticale with common wheat were observed. the signal of pSc119.2 in subtelomere of rye chromosome 6RL in all analysised plants of the third generation of MQ and F1 between the second generation of MQ and MY26 were absence, rye chromosome fragments and wheat-rye translocations were also found in some plants in the third generation of MQ and F1 between the second generation of MQ and MY26. This phenomenon was reported rarely before.6. The variations of rye chromosome in the progenies that from selfing and hybrids between primary octoploid triticale and common wheat with different seed setting ratio were also analysised. In the progeny of highest selfing seed setting ratio (the third generation of MQ4),3R and 7R hadn’t losing and they were transmitted completely; in the progeny of moderate selfing seed setting ratio (the third generation of MQ20), the appearing frequency of 3R was 83.3%; in the progeny of lowest selfing seed setting ratio (the third generation of MQ15),. the appearing frequency of 3R was 33.3%. In the progeny of highest hybridization seed setting ratio (F1 between the second generation of MQ17 and MY26), the appearing frequency of 4R was 71.4%, and it was the highest; in the progeny of moderate hybridization seed setting ratio (F1 between the second generation of MQ6 and MY26), the appearing frequency of 4R was 90.9%, and it was the highest; in the progeny of lowest hybridization seed setting ratio (F1 between the second generation of MQ12,14,15 and MY26), the appearing frequency of 1R was 72.7%, and it was the highest. The results provide a certain basis for relationship between seed set radio and rye chromosomes.