Development of self-fertile deletion homozygous and ditelosomic lines for the long arm of chromosome 2A in common wheat.

Most deletions for the short arm of chromosome 2A (2AS), and the telocentric chromosome for the long arm of chromosome 2A (2AL), are available only in the heterozygous condition in 'Chinese Spring' hexaploid wheat. This is due to the female sterility, and therefore self-sterility, of their homozygotes, caused by the partial or entire loss of the 2AS chromosome arm on which genes for normal synapsis and female fertility are located. On the other hand, a D-genome disomic substitution line 2D(2A) of 'Langdon' tetraploid wheat, in which chromosome 2D is disomically substituted for chromosome 2A, is available (i.e., self-fertile) despite chromosome 2A being missing in this line. This fact indicates that another gene for female fertility must be present in Langdon 2D(2A). We attempted to develop self-fertile 2AS homozygous deletion and ditelosomic 2AL lines by transferring this female fertility gene, through a series of crosses and cytological screening, from Langdon 2D(2A) to the two aneuploid lines. We finally obtained self-fertile 2AS homozygous deletion and ditelosomic 2AL lines. These lines displayed normal meiotic chromosome pairing and lacked all 12 of the 2AS markers used for PCR analysis.

Development of a self-fertile ditelosomic line for the long arm of chromosome 4B and its characterization using SSR markers.

The ditelosomic line for the long arm of chromosome 4B (4BL) of Chinese Spring (CS) wheat is not available because it is completely male sterile. Since all deletions in the 4B short arm (4BS) cause male sterility in the homozygous condition, a male-fertility gene should be located in a distal region of 4BS. Among the selfed progeny of a hybrid between a male-sterile 4BS deletion plant (4BS-8) and a Japanese common wheat cultivar Norin 61 (N61), we obtained self-fertile 4BS-8 homozygous deletion plants. We also found fertile nullisomic-4B plants among the selfed progeny of a hybrid between a monosomic line 4B of N61 and CS. This fact suggested that N61 has a novel male-fertility gene on a chromosome other than 4B. We established a self-fertile ditelosomic 4BL line after backcrossing a fertile 4BS-8 plant to CS monotelodisomic 4BL. By cytological observation and PCR analysis using 16 SSR markers, we verified that this ditelosomic line lacked the entire 4BS arm and found that three of the markers were on 4BS. We conducted deletion mapping using three 4BS homozygous deletion lines and three 4BS-specific markers.