CHROMOSOME STABILITY IN MAIZE (ZEA MAYS) TISSUE CULTURES AND SECTORING IN SOME REGENERATED PLANTS

Abstract

Cytogenetic stability of maize (Z. mays L.) tissue cultures was assessed by meiotic analysis of plants regenerated from 4- and 8-month-old tissue cultures and by mitotic analysis of cultured cells 4 and 8 mo. after culture initiation. Cultures initiated from 4 embryos each of W22 R-nj R-nj .times. A188 and A188 .times. W22 R-nj R-nj were examined. After 4 mo. in culture, only 1 of 65 regenerated plants was abnormal; after 8 mo., only 4 of 59 regenerated plants were abnormal. Three of the 5 abnormal plants had normal and cytogenetically abnormal sectors in the tassels. Inheritance studies were conducted on 51 regenerated plants. Eight plants segregated in the S1 for recessive mutations resulting in defective kernels, and 1 plant segregated for a recessive mutation resulting in a wilted phenotype. Eight different plants that produced normal S1 progeny segregated for defective kernel mutations in some S1 families, indicating a lack of concordance between male and female reproductive cells in the original regenerated plant. The cytogenetic stability observed in regenerated plants also was observed in vitro, indicating that selection at the time of regeneration did not occur. Of the 449 cells analyzed in 4-mo.-old cultures, 434 (97%) had the normal 20-chromosome complement; 377 (95%) of the 398 cells analyzed in 8-mo.-old cultures were normal. These results indicate that chromosome stability is maintained in tissue cultures of A188 .times. W22 R-nj R-nj maize.