Parameters Evaluated

Half of the plants were harvested to evaluate growth parameters at 11 weeks after sowing (WAS) while the other half were at 13 WAS when mature seeds had been produced. Days to flowering was recorded as the date when more than 90% of the plants had an open flower. At harvest, plant height was measured as the distance from the soil level to the tip of the uppermost leaf. The number of pods and seeds per plant was counted at maturity. The above ground biomass was measured by placing the entire plant in labeled paper bags, and then oven dried at 70°C for 48 h prior to weighing. The duct tape that sealed the joints of the 3 tube sub-sections was removed, then a knife was used to cut and separate each tube into their respective A, B, and C horizons. The soil of each sub-section was then washed away gently on a sieve with 0.5 mm mesh size to minimize root loss. The washed roots were placed in labeled Ziploc bags, and debris and dead roots from the soil were manually removed. Root traits were measured using commercial software WinRHIZO^TM (Regent Instruments Inc., Canada, 2013) to determined total root length (TRL), total root surface area (TRSA), root length per unit volume of soil [referred to as root length density (RLD)], total root volume (TRV), the mean root diameter (MRD), root volume (RV), the total number of root tips (TRT) and the total number of root forks (TRF) in each horizon. WinRHIZO^TM also generated additional output that categorize root traits into six diameter classes: 0 – 0.5 mm, >0.5 – 1 mm, >1 – 1.5 mm, >1.5 – 2.0 mm, >2 – 3.5 mm, and >3.5 – 4.5 mm. The proportion of roots in each class was calculated as percentage of the total for each of the three root tube sections.

Before root analysis, the number of nodules in each horizon of the soil for each species/genotype was counted and photographed. After WinRHIZO^TM analysis, the roots from each horizon were placed in labeled paper bags, oven dried at 70°C for 48 h and then weighed to obtain root dry weight. The set of plants that continued to grow were enclosed in fine mesh bags to prevent shattering loss and harvested when greater than 80% of seeds were dried on each plant. The number of seeds, seed weight and thousand grain weight were determined for each species/genotype.