First nuclear DNA C-values for another 25 angiosperm families

Nuclear DNA C-value is an important genomic biodiversity character with man y uses. An international workshop sponsored by Annu Is of Botany and held a t the Royal Botanic Gardens, Kew, UK, in 1997 identified major gaps in our knowledge of plant DNA C-values and recommended targets for new work, Impro ved taxonomic coverage was highlighted as a key need for angiosperms, espec ially at the familial level. In 1997 C-values were known for only approx. 3 2 % of angiosperm families; a goal of complete familial representation by 2 002 was recommended. A review published in 2000 (Bennett et al.; Annals of Botany 86: 859-909) noted poor progress towards this aims of the 691 first C-values for species only 12 (1-7 %) were for unrepresented families. We be gan new work to address this in 1999, reporting first DNA C-values for 25 a ngiosperm families in 2001 (Hanson et al.; Annals of Botany 87: 251-258). H ere we report first DNA C-values for a further 25 angiosperm families, incr easing familial coverage in angiosperms to approx. 45 %. Such targeting rem ains essential to approach the goal set by the 1997 workshop of familial co verage for angiosperms within 5 years. The 4C DNA amounts presented here ra nge from 0.76 pg (similar to Arabidopsis thaliana) in Roridula gorgonias (R oridulaceae) to 29.74 pg in Gunnera manicata (Gunneraceae). 1C values were < 3.5 pg in 23 of the 25 families; these data provide further support for t he view that ancestral angiosperms almost certainly had small genomes (defi ned as 1C <less than or equal to> 3.5 pg). Chromosome counts are reported f or 20 taxa, including first records for one genus and five species. (C) 200 1 Annals of Botany Company.