How many macrogametophytes per individual should be analyzed to genotype conifer seed trees at genetic markers?

PASTORINO, MARIO JUAN; GREGORIUS, HANS-ROHLF

Forest Genetics

Arbora Publishers

Lugar: Zvolen (Eslovakia); Año: 2002 vol. 9 p. 47 - 53

1335-048X

Each macrogametophyte in gymnosperms, usually called endosperm, represents a single meiotic event in the parental plant, and it is genetically identical with the ovule of the corresponding seed. This particularity of conifer seeds is typically used to prove the mode of inheritance of isozyme markers and subsequently to genotype seed trees for those markers to be used in population studies. In population studies several macrogametophytes must be analyzed for each single tree in order to deduce heterozygosity (if different haplotypes are found) or infer homozygosity (if only one haplotype is found). Sampling of macrogametophytes of a tree entails statistical error in genotyping. Yet, the probability of misclassification of homozygosity can be controlled. It is well known that this probability is a function of the number of macrogametophytes surveyed, and formulae are available for the single-locus case. The multiple-locus case still awaits explicit analysis. The present paper shows how in this case the error probability depends on the number of analyzed loci. Finally, the multiple-locus multiple-tree case is analyzed. For each of the three cases the proper minimum sample size of macrogametophytes to genotype conifer seed trees is specified. The relevance of the results is demonstrated for several examples taken from the literature.