Aneuploidy in Guava (Psidium guajava L.)

I. Mechanism of variation in chromosome number

Abstract

To understand the mechanism of variation of chromosome numbers in the progeny of triploid guava, the cytological and other aspects were investigated.
Due to autotriploid nature of the seedless guava, the association of chromosomes at met. I varied considerably, which in turn had profound influence on anaphase I separation.
The separation pattern at ana. I with 14-19 chromosomes was highest (24%), and lowest in 8-25 separation (2%). The frequency of all the chromosomes going to one pole was 6 percent.
Although the stainability of pollen grains were 44 percent in triploid, they were ineffective in fertilization. The progeny raised from open pollinated seeds were, therefore, the result of pollination from diploid plants.
From the frequency of observed and expected progeny, the gametic selection was inferred. The gametes with very high and low chromosome numbers appeared to be eliminated, as no plant beyond 34 somatic chromosome numbers were observed in the progeny. The frequency of occurrence of more plants with 22 and 24 somatic chromosomes clearly supported the theory of gamete selection.