FLOW CYTOMETRIC AND FEULGEN DENSITOMETRIC - ANALYSIS OF GENOME SIZE VARIATION IN PISUM

A DAPI and ethidium bromide flow cytometric and Feulgen densitometric analysis of genome size variation in Pisum was conducted. The material included 38 accessions of P. sativum of widely different geographic o rigin and altogether 14 samples of P. elatius, P. abyssinicum, P. humi le and P. fulvum. The relative genome size values obtained with the th ree staining methods were strongly correlated. No evidence for genome size variation was found among P. sativum cultivars. In particular, ce rtain Italian cultivars, for which strongly deviating C-values have be en reported, proved to be invariant. The only occasion when ambiguous evidence for marginal genome size variation was found was when all 38 accessions taxonomically affiliated with P. sativum were considered. P isum abyssinicum and P. fulvum differed from P. sativum by about 1.066 - and 1.070-fold, respectively; 1 accession of P. humile differed by 1 .089-fold, and 2 of P. elatius by 1.122- and 1.195-fold, respectively (ethidiumbromide comparison), while the other accessions of these taxa were not different from P. sativum. This variation may indicate taxon omic inhomogeneity and demands further investigation. Cultivated P. sa tivum has long been suspected of not being constant with respect to ge nome size. As shown here, these findings were not based on genuine dif ferences, but rather were technical in origin.