Mapping RFLP loci in maize using B-A translocations.

Plants hypoploid for specific segments of each of the maize (Zea mays L.) chromosomes were generated using 24 different B-A translocations. Plants carrying each of the B-A translocations were crossed as male parents to inbreds, and sibling progeny hypoploid or not hypoploid for specific chromosomal segments were recovered. Genomic DNAs from the parents, hypoploid progeny, and nonhypoploid (euploid or hyperploid) progeny for each of these B-A translocations were digested with restriction enzymes, electrophoresed in agarose gels, blotted onto reusable nylon membranes, and probed with nick-translated, cloned DNA fragments which had been mapped previously by restriction fragment length polymorphism (RFLP) analysis to the chromosome involved in the B-A translocation. The chromosomal segment on our RFLP map which was uncovered by each of the B-A translocations was determined. This work unequivocally identified the short and long arms of each chromosome on this map, and it also identified the region on each chromosome which contains the centromere. Because the breakpoints of the B-a translocations were previously known on the cytological and the conventional genetic maps, this study also allowed this RFLP map to be more highly correlated with these maps.