Cultural treatments for accelerated growth and flowering of Panicum virgatum

Abstract

Background: Exploiting heterosis through hybrid breeding is essential to increase biomass yields of switchgrass (Panicum virgatum). However, life cycle timespan for clone evaluation for field evaluation is a major limitation to genetic selection. Methods & results: In an attempt to shorten the switchgrass life cycle timespan, we investigated the effect of four variables on the vegetative and reproductive morphology of the P. virgatum cultivar “Alamo”: day length, temperature, container size, and application of plant growth regulators. Seedlings grew fastest and reached flowering fastest under 18 hours of daylight with growth being severely and mildly inhibited at 8 h and 23 h, respectively. Under the optimum (18 h) photoperiod, day temperature of 25°C led to the fastest growth and flowering whereas a 5°C increase or decrease inhibited growth and flowering. Within the 18 h/25°C treatment, 44% of plants flowered after 90 d and >15% of plants reached full anthesis or post-anthesis seed set. Conclusions: Allowing 45 d for seed set and 30 d for cold stratification, generation time for the post-anthesis plants grown in 18 h/25°C conditions is approximately 165 days, allowing for the production of two generations of switchgrass per year for accelerating germplasm development for this perennial bioenergy crop.