ANALYSIS OF ACTIVE NUCLEOLUS ORGANIZING REGIONS IN CAPSICUM (SOLANACEAE) BY SILVER STAINING

Nucleolar activity of 22 samples belonging to nine diploid species of Capsicum was analyzed in somatic metaphases and interphase nuclei. The y are: C, chacoense, C. parvifolium, C. frutescens, C. chinense, C. an nuum var. annuum, C. baccatum var. pendulum, C. pubescens, all with 2n = 24, and C, mirabile var. mirabile and C. campylopodium with 2n = 26 . Silver staining was applied for the first time in Capsicum, providin g useful markers for chromosome identification in combination with oth er banding techniques already employed in the genus. From two to eight AgNORs (silver-stained nucleolus organizing regions) were found in th e diploid complement of the taxa studied. Nucleolar organizers are loc ated at secondary constrictions of chromosomes which are conventionall y stained or banded (C-banding or fluorochrome banding). Polymorphism of AgNORs and attached satellites often occurs. Nucleoli are usually f used to a variable extent. Number and position of active rDNA loci are variable not only between but also within species and populations. Ho mologies in position of NORs between species were established. The dat a obtained are related to previous conclusions on phylogenetic relatio nships in Capsicum. Possible trends of karyotype evolution concerning nucleolar organizers are discussed, and four NORs in the diploid compl ement (on chromosome pairs #1 [m] and #12 [st]) are regarded as the pl esiomorphic condition.