Mapping of dv and el

dv/dv plants were crossed by a portion of the B-A translocation series. The various progeny families were grown and enriched for hypoploids and, subsequently, sporocyte samples were taken. The following chromosome arms can probably be excluded from further consideration since no sporocytes with a divergent spindle phenotype were seen:
 
arm 1S TB-1Sb 9 samples taken
arm 5S TB-1La-5S8041 37 samples taken
arm 5L TB-5La 26 samples taken
arm 6S TB-6Sa 70 samples taken
arm 7L TB-7Lb 33 samples taken
arm 9S TB-9Sd 19 samples taken

Work involving the remaining arms is continuing.

Families segregating el/el plants were also crossed by some of the B-A translocations. The progeny from these crosses were grown and sporocyte samples were taken. Based upon cytological examination of sporocytes, tentative placement of el (elongate) on the long arm of chromosome 8 can be made. Two separate crosses of TB-8Lc onto plants in families segregating el/el were obtained. Among the progeny of the first cross, a hypoploid (determined cytologically) appeared phenotypically el. A total of twelve sporocytes, were examined from this cross; those which were phenotypically El were not further analyzed. In the second cross, one hypoploid among the eight sporocyte samples taken also showed an el phenotype.

One must remember that the el phenotype is extremely variable in expression. el/el segregants in families can be difficult to discern since they may show no more pollen abortion than their normal sibs. In other backgrounds or under different environmental conditions, el/el plants may be nearly male-sterile. In the above two 8L hypoploids, early anaphases appeared normal and, as the segregation of chromosomes continued, the el phenotype became apparent.

The cross of el/el plants by TB-8Lc will be made again to confirm these preliminary results. Meanwhile, an allelism test between el and ms8, which is located on 8L, will be made and a linkage study of el and several 8L markers will be started.

Chris Curtis


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