Mitotic chromosome numbers and measurements were determined from enzymatically digested shoot tips for 14 species of Rosa, subgenus Hulthemia, Platyrhodon, and Rosa (the latter represented by sections Pimpinellifoliae, Cinnamoneae, Synstylae, Banksianae, Laevigatae, and Bracteatae). All were 2n = 14 or 2n = 28, as expected from previously published chromosome counts in Rosa. Arm lengths of chromosome pairs measured from digitized images were analyzed for similarity using a least-squares algorithm. On this basis, tetraploid species were compared to their diploid relatives. This study demonstrates the value of karyotypic data in combination with morphological and ecological information for examining the evolution of Rosa.
Yan Ma, David H. Byrne, and David M. Stelly
Claudine M. Bona, Jean H. Gould, J. Creighton Miller, David M. Stelly Jr., and Eliezer S. Louzada
The highly appreciated Euvitis subgenera species (2n=38) are very susceptible to pests and diseases. Tolerance/resistance may be found in the closely related Vitis rotundifolia cultivars (2n=40), but the poor rooting characteristic of this species is a problem, and conventional crossings between Euvitis and V. rotundifolia are complicated because of different chromosome numbers. Therefore, somatic hybridization may be an alternative for gene transference between these species. The establishment of an efficient in vitro procedure may facilitate future genetic manipulations. Furthermore, in vitro success may be an indicative of protoplast totipotency. The goal of this research was to test 11 cultivars from different species for their in vitro cultivation and protoplast isolation capacity. Different doses of benzyladenine (BA) were tested and explants were cultivated in both Lloyd and McCown's Woody Plant Medium (WPM) and Murashige and Skoog medium (MS). We established an efficient in vitro procedure and plants of C. sauvignon, Syrah, SV 12-375, Scuppernong, Magnolia, Higgens and B. beauty were regenerated. No rooting problem was observed in vitro. Black spanish and Herbemont callus were kept in vitro, but plants were not regenerated. SV-12327 and Jumbo died. WPM was more efficient than MS for most cultivars. The V. vinifera cultivars C. sauvignon and Syrah developed well in both media. Protoplast isolation was more efficient using leaves rather than callus or suspension cells. BA at 3 μM·L-1 induced organogenesis while 10 μM·L-1 induced callogenesis except for Syrah, where 1 μM·L-1 induced organogenesis. Protoplasts were isolated from Herbemont and C. sauvignon and microcallus were obtained.
Yan Ma, M. Nurul Islam-Faridi, Charles F. Crane, David M. Stelly, H. James Price, and David H. Byrne
To our knowledge, there has been no published technique to produce consistently high-quality slides of somatic chromosomes of roses (Rosa sp.). Therefore, various pretreatments, fixatives, digestions, stains, and maceration and squashing methods were tested to identify a procedure to produce clear, well-spread chromosomes from shoot tips. The best results were obtained after pretreatment in a mixture of 0.1% colchicine and 0.001 m 8-hydroxyquinoline for 4 h, and fixation in 2 acetone: 1 acetic acid (v/v) with 2% (w/v) polyvinylpyrrolidone. The darkest-stained chromosomes were obtained with carbol-fuchsin staining of air-dried cell suspensions that had been spread in 3 ethanol: 1 acetic acid (v/v).
Karen R. Harris-Shultz, Susana Milla-Lewis, Aaron J. Patton, Kevin Kenworthy, Ambika Chandra, F. Clint Waltz, George L. Hodnett, and David M. Stelly
Zoysiagrass (Zoysia sp.) is used as a warm-season turfgrass for lawns, parks, and golf courses in the warm, humid and transitional climatic regions of the United States. Zoysiagrass is an allotetraploid species (2n = 4x = 40) and some cultivars are known to easily self- and cross-pollinate. Previous studies showed that genetic variability in the clonal cultivars Emerald and Diamond was likely the result of contamination (seed production or mechanical transfer) or mislabeling. To determine the extent of genetic variability of vegetatively propagated zoysiagrass cultivars, samples were collected from six commercially available zoysiagrass cultivars (Diamond, Emerald, Empire, JaMur, Meyer, Zeon) from five states (Arkansas, Florida, Georgia, North Carolina, Texas). Two of the newest cultivar releases (Geo and Atlantic) were to serve as outgroups. Where available, one sample from university research plots and two samples from sod farms were collected for each cultivar per state. Forty zoysiagrass simple sequence repeat (SSR) markers and flow cytometry were used to compare genetic and ploidy variation of each collected sample to a reference sample. Seventy-five samples were genotyped and an unweighted pair group method with arithmetic mean clustering revealed four groups. Group I (Z. japonica) included samples of ‘Meyer’ and Empire11 (‘Empire’ sample at location #11), Group II (Z. japonica × Z. pacifica) included samples of ‘Emerald’ and ‘Geo’, Group III (Z. matrella) included samples of ‘Diamond’ and ‘Zeon’, and Group IV (Z. japonica) consisted of samples from ‘Empire’, ‘JaMur’, ‘Atlantic’, and Meyer3 (‘Meyer’ at sample location #3). Samples of ‘Empire’, ‘Atlantic’, and ‘JaMur’ were indistinguishable with the markers used. Four samples were found to have alleles different from the respective reference cultivar, including two samples of ‘Meyer’, one sample of ‘Empire’, and one sample of ‘Emerald’. Three of these samples were from Texas and one of these samples was from Florida. Three of the four samples that were different from the reference cultivar were university samples. In addition, one sample, Empire11, was found to be an octoploid (2n = 8x = 80). For those samples that had a fingerprint different from the reference cultivar, contamination, selfing, and/or hybridization with other zoysiagrasses may have occurred.