GENETICS OF PAPPUS PART NUMBERS IN MICROSERIS HYBRID-B87 .2. A 2ND MARKER ENZYME IN THE GENETICS OF PAPPUS PART NUMBERS IN MICROSERIS HYBRID-B87 (ASTERACEAE, LACTUCEAE)

Crossing M. pygmaea (10 pappus parts) with M. bigelovii (5 pappus parts) results in hybrids with variable pappus part numbers between 5 and 10. A system of 4 additively acting genes determines the average pappus part numbers of these hybrids. In hybrid B 87 2 genes have a 10-determining and a 5-determining allele each, two others a 5-determining and a null (inactive or missing) allele. Genetic linkage of one of the latter with the enzyme gene Esterase-1 and the leaf shape gene spatulate leaves was demonstrated. Linkage was demonstrated between one of the 2 10-determining genes and the enzyme locus Esterase-Y/B. The genotypes in the pappus part system of many specimens can now be fully determined. This is a major advance for the analysis of the evolution of this additive polygenic system.