Genetic control of B chromosome transmission rate in Zea mays ssp. mays (Poaceae)

We selected genotypes of high and low B chromosome transmission rate (TR) in a native race of maize (Pisingallo) from northwest Argentina. We made 20 female OB male IB and 20 f.IB m.OB crosses. The former (GOm) showed a large variation of B TR, with a mean of TR ± SE = 0.52 ± 0.06, ranging from 0.17 to 0.98. In the latter (GOf) the mean was TR = 0.47 ± 0.02 ranging from 0.31 to 0.58. Plants showing the highest and the lowest TR were selected to constitute the progenitors of the G1 generations. We made 19 f.0B m.2B crosses, studying 24–30 plants per cross. The TR of the high (H) and low (L) lines in Glm (GlmH and GlmL) significantly differed (TRH = 0.65 ± 0.03, TRL = 0.40 ± 0.01), indicating that the H and L lines are different groups. The large variation in male TR suggests that preferential fertilization of gametes carrying B chromosomes does not always occur. We also selected plants showing high and low TR in the progenies of f.lB m.OB crosses (GOf), and made 24 f.1B m.0B crosses, studying 23–30 plants per cross. The TRs of the H and L lines in G1f (GlfH and GlfL) were significantly different (TRH = 0.48 ± 0.025, TRL = 0.40 ± 0.02). The TRs in G0f and G1fL were significantly different (TR = 0.47 ± 0.02 and 0.40 ± 0.02, respectively), while this was not the case between G0f and G1fH. Our results demonstrate the existence of genotypes controlling B TR in this native population of maize.     

Bases and spaces: resources on the web for accessing the draft human genome - II - After publication of the draft

The volume of human genome sequence and the variety of web-based tools to access it continue to grow at an impressive rate, but a working knowledge of certain key resources can be sufficient to get the most from your genome. This article provides an update to Genome Biology 2000, 1(4):reviews2001.1-2001.5.