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.
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