THE EFFECT OF GENOME AND SEX ON RECOMBINATION RATES IN PENNISETUM SPECIES

The effects of homoeology and sex on recombination frequency were stud ied in crosses between cultivated pearl millet, Pennisetum glaucum, an d two wild subspecies, P. violaceum and P. mollissimum. For the two wi ld x cultivated crosses, reciprocal three-way crosses were made betwee n the F-1 hybrid and an inbred line (Tift 23DB(1)). The three-way cros s populations were mapped to produce a female map of each wide cross ( where the F-1 was the female) and a male map (where the F-1 was the ma le). Total genetic map lengths of the two inter-subspecies crosses wer e broadly similar and around 85% of a comparable intervarietal map. In the P. glaucum x P. mollissimum crosses, the map was further shortene d by a large (40 cM) inversion in linkage group 1. Comparison of the r ecovered recombinants from male and female meiocytes showed an overall trend for the genetic maps to be longer in the male (similar to 10%) in both inter-subspecific crosses; however, analysis of individual lin kage intervals showed no significant differences. Gametophytic selecti on was prevalent, and sometimes extreme, for example 12:1 in favour of 'wild' alleles in the P. glaucum x P. mollissimum male recombinant po pulation. One of the loci which determines panicle type in cultivated pearl millet and wild relatives, H, was mapped 9 cM from Xpsm812 on li nkage group 7 in the P. violaceum cross.