Heterosis for biomass yield and other traits in 'Alamo' x 'Kanlow' switchgrass populations

Heterosis plays an important role in switchgrass (Panicum virgatum L.) breeding. To identify superior clones for hybrid development through seasonal single cut, 10 crosses derived from 'Alamo' x 'Kanlow' and parents were evaluated. The experiment was planted in 2018 using a randomized complete block design with two replications at two locations in Tennessee: the East Tennessee Research and Education Center (ETREC), Knoxville, and the Plateau Research and Education Center (PREC), Crossville. The crosses and their parents were evaluated for biomass yield, plant height, and clonal mass in the fall of 2019 and 2020. The crosses were significantly different in biomass yield within and across locations (P <= .05). Average biomass yield of the crosses ranged from 7.1 to 8.7 Mg ha(-1) at ETREC and from 10.0 to 11.8 Mg ha(-1) at PREC. The crosses demonstrated an average of 46% mid-parent heterosis (MPH) and 24% high-parent heterosis (HPH) for biomass yield across the two locations. The MPH and HPH were 3 and -1.3% for plant height and 12 and 1% for clonal mass, respectively. Moderate to strong positive association was found between clonal mass scores and biomass yield at individual locations across years and across locations and years (r = 0.37-0.79, P <= .05). The association between biomass yield and plant height was inconsistent (r = -0.24 to 0.67, P <= .05). The findings of biomass yield heterosis in these crosses suggested the potential of hybrid cultivars for biomass yield improvement in lowland switchgrass.