GENOME SIZE VARIATIONS WITHIN DASYPYRUM-VILLOSUM - CORRELATIONS WITH CHROMOSOMAL TRAITS, ENVIRONMENTAL-FACTORS AND PLANT PHENOTYPIC CHARACTERISTICS AND BEHAVIOR IN REPRODUCTION

Feulgen/DNA cytophotometric determinations carried out in the root mer istem of seedlings showed that substantial quantitative alterations in the nuclear genome are present between and within 15 natural populati ons of Dasypyrum villosum in Italy. When the most variant values are c onsidered, there is a 17.6% difference between the mean genome size of the populations, and a 66.2% difference between the genome size of in dividual plants within a population. A highly significant, positive co rrelation was found to exist between the genome size of D. villosum pl ants and the altitude of their stations, and differences in DNA conten ts between individual plants were greater in populations from mountain sites. Karyological analyses showed all chromosome pairs to differ la rgely in size between plants with differing DNA contents. A highly sig nificant, positive correlation was found to exist between genome size and both the length of the chromosome complement at metaphase and the length and arm ratio of pair VII. Significant correlations were also f ound between DNA content and certain phenotypic characteristics of the plants. The mean genome size of the populations was negatively correl ated with the mean leaf length and width. In contrast, the genome size of individual plants was positively correlated with the weight of the seed from which they originated and their flowering interval. A large range of genome sizes was found in the half-sib progeny of a plant ha ving a relatively large genome. In contrast, in the half-sib progeny o f a plant having a small genome, the genome sizes of the individual pl ants were less divergent and similar to that of the mother plant. All siblings from crosses between plants with differing genome sizes had s imilar DNA contents, which were intermediate between those of the pare ntal plants, even if closer to the DNA content of the parent plant hav ing the smaller genome size. Size polymorphism within pairs was never observed in plants obtained from these crosses or in half-sibs whose g enome size differed from that of the mother plant. The intraspecific a lterations observed in the nuclear genome and their effects on plant d evelopment and phenotype are briefly discussed as evolutionary factors which allow D. villosum populations to withstand different environmen tal conditions as well as the variability of conditions in a given env ironment.