Molecular, cytogenetic, anatomical, and morphological variations associated with polyploids of prairie cordgrass

Prairie Cordgrass;Polyploidy;Chloroplast;Silver Staining;silver stained NORs AgNORs;Lodging;Morphology;Anatomy

Kim, Su Min

关键词: Prairie Cordgrass;    Polyploidy;    Chloroplast;    Silver Staining;    silver stained NORs AgNORs;    Lodging;    Morphology;    Anatomy;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/89217/KIM-DISSERTATION-2015.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Climate change or global warming, gradually increase in average global temperature, is now well documented and accepted by scientists as fact. The main cause of climate change is increasing carbon dioxide level (CO2) in the atmosphere. Bio-renewable energy sources can play a role in providing energy services to meet basic human needs in sustainable manner, in particular, in migrating climate change. However, the current bioenergy sources face both social and environmental challenges, mainly because they use food crops which lead to land-use competition between food and liquid biofuels. In order to minimize competition with food crops, the next generation bioenergy sources should be grown on marginal lands, where food crops cannot be grown.Prairie cordgrass (Spartina pectinata Link) has been recommended as a dedicate energy crop grown on marginal land. This species is tall (1-3 m), rhizomatous, C4 perennial grass, native to North America, and commonly found in lower, poorly drained soils along roadside, ditches, stress, marshes, wet meadows, and potholes. Prairie cordgrass is well known as polyploid species, including tetra- (2n=40), hexa- (2n= 60), and octoploids (2n=80), and has high abiotic stress tolerances such as salinity, cold, and waterlogging. Prairie cordgrass is successfully adapted in wide geographic distribution throughout Canada to 60° N latitude and in the United States throughout the Northeast, Great Lakes, and Midwest states, as well as most other states.According to previous studies, U.S. geographic distribution of this species is closely related to ploidy levels.Only tetraploid populations are found in the New England region, while most octoploids are distributed in the West North Central regions. Populations of tetra- and octoploids were found in close proximity in the West North Central and the West South Central regions.Unlike tetra- and octoploids, neo-hexaploids have only been reported in a single location co-existing with tetraploids.Since the polyploid evolutionary process in prairie cordgrass is dynamic, it is critical to understand how the polyploidization events influence on genetic diversity, chromosome structural changes, and morphological variations within the species. Through chloroplast DNA (cpDNA) phylogenetic analyses, three distinct genetic haplotypes were identified, which are relatively associated with geographic distribution and ploidy level. Genetic diversity in polyploids has resulted in variation in the number of silver stained NORs (AgNORs) on chromosomes at metaphase. The distribution patterns of AgNORs in metaphase cells of tetra- and octoploids appears to reflect changes in ploidy. Two populations of tetra- and octoploids have the number of AgNORs expected from their mitotic metaphase chromosome number.Four AgNORs were found in tetraploids, while octoploids have eight AgNORs. However, two hexaploids have differing numbers of AgNORs (3 and 6), indicating that chromosome structure may not be stabilized in early generations of neo-polyploidy. This recent polyploidization event also appears to have modified morphological characteristics such as stem height, thickness, and mass, which are strongly associated with lodging resistance. Hexaploid populations have higher lodging resistance than their putative tetraploid populations due to specific morphological characteristics such as shorter height or thicker and heavy stem. Overall, the past and new polyploidization events may develop novel molecular, cytogenetical, anatomical, and morphological characteristics in prairie cordgrass.Therefore, the results of this study plays an important role in understanding the creation of genetic diversity which is a critical factor for developing prairie cordgrass as a dedicated energy crop grown in stressful environmental conditions.