An attempt to use embryo-endosperm marker in obtaining CMS maize analogues
--Toma Dankov, Miglena Kruleva and Zlatka Bojilova

The method of Chase for in vivo androgenic obtaining of maize analogues is known (J. Hered. 54:152-158, 1963), and the endosperm marker created by him for this purpose, known as the marker of Chase. Because of the double fertilization in maize, the endosperm marker is not a sure guarantee for distinguishing androgenetic haploids from the hybrid seeds.

We have at our disposal an embryo-endosperm marker (Compt. Rend. Bulg. Acad. Sci., in press) which is dominantly inherited, and we created sterile analogues to it with T, S and C cytoplasm.

In 1991 in an isolation plot we pollinated the above sterile analogues (in backcross five) with Mo17, which is a universal maintainer of all three types of sterility. 165 ears were obtained in T-type, 41,028 seeds, from which 195 were without embryo and endosperm marker; in S-type, 143, 37,222 and 170 respectively and in C-type 100, 31,155 and 50. The greater part of the haploid seeds were not weak and wrinkled.

In 1992 102 plants of T-type from the seeds without marker, 91 plants of S-type and 33 of C-type were grown directly in the field. From them 38, 37 and 21 respectively were androgenic haploids and entirely female and male sterile. The 3 plants which showed female sterility from T-type, 2 from M-type and 2 from C-type were pollinated by Mo17. Only two plants of T-type and one of C-type had signs of dihaploids (of Mo17) and were also pollinated by this line. The remaining greater part of the plants were hybrid, maybe because then our sterile analogues were in BC6.

We consider that in our embryo-endosperm marker and its sterile analogues of T, S and C-type the formation of androgenic haploid seeds is heritable and can be used for accelerated creation of sterile analogues. The investigations continue. 

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