Polyploidy in Paullinia (Paullinieae, Sapindaceae) and its Systematic Implications

Abstract—Chromosome counts from 23 populations of 16 species of Paullinia (Paullinieae, Sapindaceae) from South America are given. These include first counts for ten species in six of the thirteen sections of this genus. Counts of 2n = 24 for P. cristata, P. revoluta, P. thalictrifolia, P. trigonia, P. uloptera, P. rhomboidea; 2n = 48 for P. seminuda and P. sp.; and two cytotypes of 2n = 48 and 2n = 96 for P. carpopoda and P. rubiginosa; and ca. 2n = 216 for P. cupana var. sorbilis. The chromosome number 2n = 24 appears to be conserved for this genus, however, in this contribution polyploid series are cited for the first time for some native species. These results were interpreted in a phylogenetic context.

Estimating Nuclear DNA Content in Peach and Related Diploid Species Using Laser Flow Cytometry and DNA Hybridization

Using laser flow cytometry, nuclear DNA amounts were estimated for 12 Prunus species, representing three subgenera [Prunophora (Prunus), Amygdalus, and Cerasus (Lithocerasus)], two interspecific hybrids, four cultivars, and a synthetic polyploid series of peach consisting of haploids, diploids, triploids, and tetraploids (periclinal cytochimeras). Peach nuclear DNA content ranged from 0.30 pg for the haploid nuclei to 1.23 pg for the tetraploid nuclei. The diploid genome of peach is relatively small and was estimated to be 0.60±0.03 pg (or 5.8×108 nucleotide base pairs). The polyploid series represented the expected arithmetic progression, as genome size positively correlated with ploidy level (i.e., DNA content was proportional to chromosome number). The DNA content for the 12 diploid species and two interspecific diploid hybrids ranged from 0.57 to 0.79 pg. Genome size estimates were verified independently by Southern blot analysis, using restriction fragment length polymorphism clones as gene-copy equivalents. Thus, a relatively small and stable nuclear genome typifies the Prunus species investigated, consistent with their low, basic chromosome number (× = 8).

Genetic Control of Seven Enzyme Systems in Ipomoea Species

Genetic control of seven enzymes in Ipomoea trifida (H.B.K.) G. Don. (diploid, tetraploid, and hexaploid populations) and I. batatas (L.) Lam. was studied by starch gel electrophoresis. Inter- and intraspecific polymorphisms were detected for all enzymes in the populations analyzed, except catalase (CAT, EC 1.11.1.6). Phosphoglucomutase (PGM; EC 2.7.5.1), phosphoglucose isomerase (PGI; EC 5.3.1.9), glutamate oxaloacetate transaminase (GOT; EC 2.6.1.1), menadione reductase (MNR; EC 1.6.99.2), shikimate dehydrogenase (SAD; EC 1.1.1.25), and malate dehydrogenase (MDH; EC 1.1.1.37) collectively were encoded by a minimum of 13 genetic loci resulting in 24 allozymes. Results from the diploid I. trifida were used to infer the genetic basis of these enzymes in the polyploid species. All polyploid populations shared almost the same number of allozymes with diploid I. trifida. PGM and PGI showed evidence of duplicated genes in the polyploid series. A unique allele for MNR was detected only in polyploid series.

A contribution to the taxonomy of the Oxytropis campestris complex in northwestern North America

The Oxytropis campestris complex in northwestern North America is a polyploid series comprising at least seven morphologically and geographically distinct taxa. In light of the data of the present study, the authors propose that five taxa be reelevated to species status: O. cusickii Greenm., O. monticola Gray, O. columbiana St. John. O. jordalii Porsild, O. varions (Rydb.) K. Schum.; and that two taxa be recombined as subspecies: O. monticola Gray ssp. dispar (A. Nels.) Elisens & Packer and O. jordalii Porsild ssp. davisii (Welsh) Elisens & Packer.Three different chromosome numbers are present in the complex and represent the tetraploid (2n = 32), hexaploid (2n = 48), and dodecaploid (2n = 96) condition. Three species have uniform chromosome numbers (O. cusickii, 2n = 48; O. jordalii, 2n = 32; and O. columbiana, 2n = 48), two taxa, O. varians and O. monticola ssp. monticola, exhibit two different chromosome numbers. No attempt to subdivide O. varians was undertaken as; with the exception of guard cell size, no differences were observed between hexaploid and dodecaploid representatives. At least two distinct entities appear to be present in O. monticola ssp. monticola, for, while morphologically, cytologically (2n = 32), and ecologically uniform east of the continental divide, it is quite variable in appearance and has a different chromosome number (2n = 48) west of the divide.