M. Rosato et al., GENOME SIZE AND NUMERICAL POLYMORPHISM FOR THE B-CHROMOSOME IN RACES OF MAIZE (ZEA-MAYS SSP. MAYS, POACEAE), American journal of botany, 85(2), 1998, pp. 168-174
Twenty-one native populations (1120 individuals) of maize from Norther
n Argentina were studied. These populations, which belong to 13 native
races, were cultivated at different altitudes (80-3620 m). Nineteen o
f the populations analyzed showed B chromosome (Bs) numerical polymorp
hism. The frequency of individuals with Bs varied from 0 to 94%. The n
umber of Bs per plant varied from 0 to 8 Bs. with the predominant dose
s being 0, 1, 2 and 3. Those populations with varying number of Bs sho
wed a positive and statistically significant correlation of mean numbe
r of Bs with altitude. The DNA content, in plants without Bs (A-DNA)(2
n = 20), of 17 populations of the 21 studied was determined. A 36% var
iation (5.0-6.8 pg) in A-DNA content was found. A, significant negativ
e correlation between A-DNA content and altitude of cultivation and be
tween A-DNA content and mean number of Bs was found. This indicates th
at there is a close interrelationship between the DNA content of A chr
omosomes and doses of Bs. These results suggest that there is a maximu
m limit to the mass of nuclear DNA so that Bs are tolerated as long as
this maximum limit is not exceeded.