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Flow cytometry and stomata characteristics were used for screening ploidy levels in a large population of in vitro induced autopolyploids of the Musa acuminata breeding clone SH-3362 . Culturing shoot tips in liquid medium supplemented both with 5 .0 mM colchicine for 48 hours or 30 pM oryzalin (3,5-dinitro-N4,N-dipropylsulphate) for seven days, both in combination with 2% (v/v) DMSO, resulted in a high (23 .1% and 29 .1%) frequency of non-chimeric tetraploids in the fourth vegetative generation . Although mixoploidy persisted in subsequent cycles of vegetative propagation, tetraploids as identified by flow cytometry remained solid non-chimeric during two more cycles . These autotetraploids were propagated for field testing. A rough pre-selection of regenerated V4 plants based on their stomata characteristics resulted in a population in which only 56.2% of the plants were solid tetraploids . The somatic polyploidization system reported here can be utilised for banana breeding programmes .

The leading cause of outliers appeared to be improper calibration or compromised storage of laboratory standard and primary reference waters; hence the importance of judicious storage of lab standards cannot be understated. The deprecated practice of single standard normalization was identified as a problem for some laboratories. We further recommend that laboratories strive to report parsimonious long-term precisions based upon control standards, and to improve quantification and correction for LAS instrumental drift and inter-sample carryover effects.

The diploid (2C) amount of DNA in cassava (Manihotesculenta Crantz) is 1 .67 picograms (pg) per cell nucleus . This value corresponds to 772 mega-base pairs in the haploid genome . The size of the nuclear genome in cassava is very small in comparison with other Angiosperms . Flow cytometry techniques were used to screen ploidy levels in a large population of in vitro plantlets treated with colchicine and oryzalin (3,5-dinitro-N 4,N-dipropylsulphate) . Culture of axillary node cuttings for 48 hours in liquid medium supplemented with 2 .5 to 5 .0 mM colchicine in combination with 2% dimethyl sulfoxide (DMSO) resulted in a high frequency (23 to 42%) of non-chimeric tetraploids in the V3 generation . Although mixoploidy may persist in as many as four cycles of vegetative propagation of node cuttings, solid (non-chimeric) tetraploids can be identified by flow cytometry among in vitro plantlets and then rapidly propagated for field testing . A somatic polyploidization system is proposed for implementation in cassava breeding programmes .

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