THE GENETICS OF TRIPLOID FORMATION AND ITS RELATIONSHIP TO ENDOSPERM BALANCE NUMBER IN POTATO

The ability of Solanum tuberosum Group Andigena clones to produce triploids (2n = 3x = 36) in 4x(4 endosperm balance number (EBN)) × 2x(2EBN) crosses was investigated. The difference in triploid production among the clones tested, though large, appears to be the result of low heritability. The triploids produced in the 4x × 2x crosses did not seem to bear heritable factors that improved triploid production in 2x and 4x populations derived from them. Yet, the seeds/fruit data from a similar 4x × 2x cross fit a Poisson distribution. It was argued that the low probability nonheritable random events responsible for the triploids from 4x × 2x and 2x × 4x crosses were misfertilizations, mitotic abnormalities in the gametophyte, and (or) mitotic misdivisions in the endosperm.Key words: Solanum, endosperm, triploid block, fertilization.