Switchgrass (Panicum virgatum L.) Intraspecific Variation and Thermotolerance Classification Using in Vitro Seed Germination Assay

Abstract

Cardinal temperatures for plant processes have been used for thermotolerance screening of geNotypes, geoclimatic adaptability determination and pheNological prediction. Current simulation models for switchgrass (Panicum virga-tum L.) utilize single cardinal temperatures across geNotypes for both vegetative and reproductive processes although intra-specific variation exists among geNotypes. An experiment was conducted to estimate the cardinal temperatures for seed germination of 14 diverse switchgrass geNotypes and to classify geNotypes for temperature tolerance. Strati-fied seeds of each geNotype were germinated at eight constant temperatures from 10<sup>o</sup>C to 45<sup>o</sup>C under a constant light intensity of 35 µmol m<sup>-2</sup> s<sup>-1</sup> for 12 h d<sup>-1</sup>. Germination was recorded at 6-h intervals in all treatments. Maximum seed germination (MSG) and germination rate (GR), estimated by fitting Sigmoidal function to germination-time series data, varied among geNotypes. Quadratic and bilinear models best described the MSG and GR responses to temperature, respectively. The mean cardinal temperatures, T<sub>min</sub>, T<sub>opt</sub> and T<sub>max</sub>, were 8.1, 26.6, and 45.1<sup>o</sup>C for MSG and 11.1, 33.1, and 46.0<sup>o</sup>C for GR, respectively. Cardinal temperatures for MSG and GR; however, varied significantly among geNotypes. GeNotypes were classified as sensitive (‘Cave-in-rock’, ‘Dacotah’, ‘Expresso’, ‘Forestburg’, ‘Kanlow’, ‘Sunburst’, ‘Trailblazer’, and ‘Warrior’), intermediate (‘Alamo’, ‘Blackwell’, ‘Carthage’, ‘Shawnee’, and ‘Shelter’) and tolerant (‘Summer’) to high temperature based on cumulative temperature response index (CTRI) estimated by summing individual response indices estimated from the MSG and GR cardinal temperatures. Similarly, geNotypes were also classified as sensitive (Alamo, Blackwell, Carthage, Dacotah, Shawnee, Shelter, and Summer), moderately sensitive (Cave-in-rock, Forestburg, Kanlow, Sunburst, and Warrior), moderately tolerant (Trailblazer), and tolerant (Expresso) to low temperatures. The cardinal temperature estimates would be useful to improve switchgrass models for field applications. Additionally, the identified cold- and heat-tolerant geNotypes can be selected for niche environments and in switchgrass breeding programs to develop new geNotypes for low and high temperature environments

Salinity effects on perennial, warm-season (C4) grass germination adapted to the northern Great Plains

“…Among the three parameters, a represents the maximum germination, b determines the time (day) when the midpoint of the curve occurs, and c is the slope of the curve. The logistic function has been widely used for germination data analysis (Schimpf et al 1977;Hsu et al 1984;Lafond and Baker 1986;Seepaul et al 2011). Equation 1 was chosen because it can be easily manipulated for estimating parameters either by linear or nonlinear regression and the natural logarithm of time (d) removed the skewness in the data (Schimpf et al 1977;Lafond and Baker 1986).…”

Methods for breaking seed dormancy of ryegrass during storage periods

“…It was not recommended as a method to break the dormancy of ryegrass seeds. Studies conducted with forage species reveal that the optimum temperature for germination is specific for each cultivar and that seeds do not germinate at temperatures above 45°C (Seepaul et al, 2011).…”

Stress-Tolerant Feedstocks for Sustainable Bioenergy Production on Marginal Land

“…[86,234] (Table 4) (Table 4). Commonly cultivated Panicum virgatum cultivars "Alamo," "Cave-inRock," and "Kanlow" were sensitive or moderately sensitive to low temperatures [243]. Although many Agave species are associated with warm desert ecosystems, a number of Agave spp.…”

“…"Alamo" and others) to high tolerance (cv. "Summer") to heat stress during germination [243] and thus may be good candidates for production on marginal lands in warm regions. Commonly grown cultivars "Cave-in-Rock" and "Kanlow" were heat sensitive [243].…”

“…"Summer") to heat stress during germination [243] and thus may be good candidates for production on marginal lands in warm regions. Commonly grown cultivars "Cave-in-Rock" and "Kanlow" were heat sensitive [243]. Heat-tolerant woody species include Jatropha curcas, and Eucalyptus occidentalis and others, Pinus densiflora and others, Populus euphratica, Robinia pseudoacacia, and Salix nigra ( Table 5).…”