Dihaploid Stocks of Switchgrass Isolated by a Screening Approach
- PDF / 462,284 Bytes
- 9 Pages / 595.276 x 790.866 pts Page_size
- 32 Downloads / 159 Views
Dihaploid Stocks of Switchgrass Isolated by a Screening Approach Hugh A. Young & Bradley J. Hernlem & Amy L. Anderton & Christina L. Lanzatella & Christian M. Tobias
Published online: 14 February 2010 # Springer Science+Business Media, LLC. 2010
Abstract Manipulation of ploidy in switchgrass has potential to accelerate inbred production and to provide insight about genome structure through either sequencing or cytogenetic approaches. We have identified two dihaploid individuals isolated from among the progeny of a controlled cross between two individuals of the cultivars Alamo and Kanlow. The dihaploid lines were initially distinguished from the parental lines by their reduced heterozygosity and were subsequently confirmed through estimation of C values by flow cytometry and chromosome counts of metaphase root tip squash preparations. These plants are functionally sterile, with floral bracts that remain closed and inviable pollen. They can be easily distinguished from tetraploid individuals by their reduced stature, smaller epidermal cell size, and lower number of chloroplasts per guard cell. Aberrant meiosis in these individuals is evidenced by a lack of regular pairing at diakinesis and metaphase I and suggests that the nonhomologous genomes are distinct from one another. The reduced genome size of these dihaploids will facilitate basic genome studies and genetic analyses that are impossible or problematic in polyploid accessions.
H. A. Young : A. L. Anderton : C. L. Lanzatella : C. M. Tobias (*) Genomics and Gene Discovery Research Unit, USDA-ARS, Western Regional Research Center, 800 Buchanan Street, Albany, CA 94710, USA e-mail: [email protected] B. J. Hernlem Produce Safety Research Unit, USDA-ARS, Western Regional Research Center, 800 Buchanan Street, Albany, CA 94710, USA
Keywords Bioenergy . Switchgrass . Cytogenetics . Perennial biofeedstocks . Dihaploids . Biomass . Renewable energy . Polyploidy
Introduction Due to its highly productive perennial habit, water use efficiency, and low nitrogen requirements, switchgrass (Panicum virgatum L.) is viewed as a promising source of biomass for renewable energy production. The base chromosome number for switchgrass and other Panicum sp. is believed to be 9 [16], but the species is a complex of different cytotypes. Tetraploid (2n=4x=36) and octoploid (2n=8x=72) cytotypes predominate, although diploids, hexaploids, duodecaploids, and aneuploids have been reported [9, 12, 17, 30, 33, 35, 38]. It is still unclear if gene flow between cytotypes is common in natural populations. Artificial crosses between octoploids and tetraploids are not usually successful [28, 41]. Lowland ecotypes are mainly tetraploid and are found in the southern range of the species distribution, while upland ecotypes are associated with several different cytotypes and have a wide geographical distribution. Some populations appear to exist as mixtures of ploidy levels. Mixed ploidy has been observed in seed lots obtained from germplasm repositories and commercial seed sources [32]
Data Loading...
