Ja. Sandoval et al., CHROMOSOME-NUMBER VARIATIONS IN MICROPROPAGATED TRUE-TO-TYPE AND OFF-TYPE BANANA PLANTS (MUSA-AAA-GRANDE-NAINE-CV), In vitro cellular & developmental biology. Plant, 32(1), 1996, pp. 14-17
The objective of the present study on banana plants (Musa AAA Grande N
aine cv.), obtained by in vitro shoot tip culture, was to determine wh
ether modifications in chromosome number could account for the appeara
nce of the off-types with mosaiclike leaf defects or dwarf stature, th
e most frequent off-types observed after micropropagation. Chromosome
counts were conducted on shoot tip samples treated with 8-hydroxyquino
line, digested in pectinase and stained with Schiff's reagent. On aver
age, 160 counts were made for each treatment. Four types of plant mate
rial were studied: phenotypically true-to-type plants, dwarf off types
, mosaiclike off-types obtained by micropropagation, as well as true-t
o-type plants obtained by standard propagation techniques of suckers w
ith no micropropagation history. Some cells from all four types of pla
nt material were found to have an abnormal chromosome number (i.e., 2n
= 3x = 33), characteristic of triploid bananas. The percentages of an
euploid cells were 14%, 22%, 35%, and 5%, respectively. Descending ane
uploidy was noted in micropropagated plants derived from true-to-type
and dwarf off-type suckers. The statistical analysis revealed that the
two latter types of plant material had the same percentage of aneuplo
id cells. Thus, the dwarfism could not be correlated with a change in
the chromosome number. Conversely, ascending aneuploidy was observed i
n the mosaiclike material, with 34 or 35 chromosomes in almost 28% of
the cells. This percentage was significantly higher than in true-to-ty
pe plants and highlight the genetic origin of the mosaiclike variation
.