RC Big Rock

Switchgrass

Variety Description

Varieties used for comparison: 'RC Chippewa', 'Cave-in-Rock', 'Shawnee' and 'Blackwell'

Summary: The panicles of ‘RC Big Rock' emerge later than those of ‘RC Chippewa'. The plants of ‘RC Big Rock' have fewer tillers than the plants of ‘Cave-in-Rock', ‘Shawnee' and ‘Blackwell'. The stem width at the midpoint of the 3rd internode from the bottom of the plant of ‘RC Big Rock' is broader than those of ‘Cave-in-Rock', ‘Shawnee' and ‘Blackwell'. At the soft dough stage, the widest point of the penultimate leaf of ‘RC Big Rock' is wider than those of ‘Shawnee' and ‘Blackwell'. At maturity, the plants of ‘RC Big Rock' are taller than the plants of ‘Cave-in-Rock' ‘Shawnee' and ‘Blackwell'. The plants of ‘RC Big Rock' mature later than those of ‘RC Chippewa' and ‘Blackwell'.

Description:

PLANT: octoploid, agricultural or conservational utilisation, panicles emerge late in the season, erect to semi-erect growth habit at the soft dough stage, low number of total vegetative and reproductive tillers, matures late in the season

FLAG LEAF: erect to semi-erect attitude
LEAF BLADE: blue green on upper side, broad at widest point

STEM: medium to high number of internodes
INTERNODE (3RD INTERNODE FROM BOTTOM OF PLANT): broad at mid-section

PANICLE: medium to long

Origin & Breeding History: ‘RC Big Rock' originated from seed harvested in 2006 from 30 plants of the upland switchgrass variety ‘Cave-in-Rock' grown in a field in St. Timothée, Quebec. Having survived over 10 winter seasons, 30 plants from this field were visually selected for maturity, plant height, growth habit, lodging, biomass production and disease reaction and 10 % of the heaviest harvested seed was retained. In the spring of 2007, the seed was sown outdoors into 1000 cell trays. Two hundred seedlings from these cell trays were selected based on robustness and reduced tillering and transplanted into a space-plant nursery with no fertilizer applied. In 2009, further selections were made based on time of heading, maturity, plant height, biomass yield per tiller, leaf habit, stem thickness, lodging, tiller number and visual assessment of disease reactions. In the fall of 2009, pre breeder seed production commenced by harvesting 12 tillers of selected plants which was threshed and the seed cleaned for increase.

Tests & Trials: The comparative trials for ‘RC Big Rock' were conducted by REAP Canada during the 2022 and 2023 growing seasons at the Emile A. Lods Agronomy Research Centre, at the MacDonald Campus of McGill University in Sainte-Anne-de-Bellevue, Quebec. Plots were arranged in a RCB design with 3 replicates per variety per year. Each plot measured 2.4 x 1.8 metres, containing 20 plants, resulting in 60 plants per variety per year. Measured characteristics were based on 30 measurements per variety per year. Mean differences were significant at the 5% confidence probability level based on a post hoc Tukey's Honest Significant Difference Test.

Comparison tables for 'RC Big Rock' with reference varieties 'RC Chippewa', 'Cave-in-Rock', 'Shawnee' and 'Blackwell'

Time of panicle emergence (number of days from January 1 to when the panicle can be seen on 50% of the plants)

Tiller number (total number of reproductive and vegetative tillers)

Stem width (at the midpoint of the 3rd internode from the bottom of the plant) (mm)

Penultimate leaf width (at widest point) (mm)

Plant height (including panicle at maturity) (cm)

Plant maturity (number of days from January 1 to beginning of senescence)

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Switchgrass: ‘RC Big Rock' (right) with reference variety ‘Cave-in-Rock' (left)

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Switchgrass: ‘RC Big Rock' (right) with reference varieties ‘Cave-in-Rock' (centre) and ‘Shawnee' (left)

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Switchgrass: ‘RC Big Rock' (left) with reference varieties ‘Blackwell' (centre) and ‘RC Chippewa' (right)