THE INFLUENCE OF B CHROMOSOMES ON THE SUSCEPTIBILITY OF MAIZE TO GAMMA IRRADIATION INDUCED DNA DAMAGE (RECOMBINATION).

Tests were conducted to ascertain whether B chromosomes influence the susceptibility of maize (Zea mays L.) plants to gamma-radiation-induced DNA damage. Isogenic stocks of Black Mexican sweet corn with and without B chromosomes were premeiotically irradiated and DNA damage was assayed by measuring pollen viability. Higher pollen viabilities relative to non-irradiated control plants were consistently obtained in irradiated plants with B chromosomes when compared to irradiated plants without B's. Furthermore, among plants irradiated with 1250R those with one B chromosome produced the greatest proportion of viable pollen and plants with increasing numbers of B's produced progressively less viable pollen. An exophenotypic trait elicited by B chromosomes is also reported. Plants with 5 or more B chromosomes often display an aberrant phenotype characterized by longitudinal white leaf stripes and/or narrow leaves. This phenotype intensifies with increasing numbers of B chromosomes and is the first case of a qualitative exophenotypic trait attributable to B chromosomes reported in maize