Studies on the effects, or lack thereof, of B chromosomes on the morphology and pollen viability in wild and cultivated plants of Xanthisma texanum (Compositae: Astereae)

Abstract

Variation in eight morphological characters of 250 plants of the annual Xanthisma texanum DC. (Compositae: Astereae) with zero to three B chromosomes was investigated within and among four populations in southwestern Oklahoma in 2 successive years. A small significant difference was found in height of the stem to the first head produced between plants with and without B chromosomes in one site in 1 year, but no significant differences in total plant height, numbers of primary and secondary branches, length of all branches, and the numbers of immature, flowering, and postflowering heads were found. No differences were found between plants in different subsites of the same population, regardless of the number of B chromosomes, but differences were found among the three populations in 1 year. The lack of effect of B chromosomes also was observed in pollen viability in a small sample of wild and cultivated plants with zero to three B chromosomes.