Characterization of crested wheatgrass germplasms for plant maturity and associated physiological and morphological traits

Abstract

Crested wheatgrass [Agropyron cristatum (L.) Gaertn.] is a drought tolerant, winter hardy perennial grass used for early spring grazing in western Canada. This grass matures early, and mature plants are not palatable for grazing animals. The objectives of this study were: 1) determine DNA content and ploidy level of 45 crested wheatgrass accessions 2) to characterize crested wheatgrass germplasm for plant maturity and associated agronomic characteristics to identify superior germplasm with late maturity; 3) to evaluate flowering time of selected germplasms of crested wheatgrass under a controlled environment. A field plot was established using 45 crested wheatgrass accessions in July 2014 at Agriculture and Agri-Food Canada (AAFC) Saskatoon Research Center at Saskatoon SK, Canada using a randomized complete block design with four replications with data collected in 2015, 2016 and 2017. On the basis of DNA content (pg 2C-1 =DNA content of diploid somatic nucleus), mean DNA content was 14.12 pg 2C-1 for diploid, 28.02 pg 2C-1 and 39.48 pg 2C-1 for tetraploid and hexaploid crested wheatgrass, respectively. Among the 45 accessions, there were 8 diploid, 31 tetraploid, and 6 hexaploid accessions. Plant maturity and other measured characteristics differed significantly among the ploidy levels. Days to heading, plant height, leaf-to-stem ratio, forage DM yield, leafiness and plant vigor and nutritive value (crude protein, neutral detergent and acid detergent fibers) differed significantly (P ≤ 0.05) among accessions at flowering stage. In this study, days to heading showed a positive correlation with leaf-to-stem ratio (r=0.23, P<0.0001), indicating that selection for later maturity in crested wheatgrass may lead to an increase in leafiness. When all 45 accessions were considered, there was a non-significant correlation between days to heading and DM yield (r= 0.07, P=0.09), but this relationship was significant (r=0.34, P<0.0001) when only Canadian breeding lines and cultivars were considered. Based on agronomic performance and nutritive value, the 45 crested wheatgrass accessions were grouped into three main clusters. In addition, ranking of days to heading among selected accessions was consistent in field and controlled environments. In conclusion, plant maturity varied within- and among- accessions, among ploidy levels, and selection for late maturity may simultaneously increase forage DM yield and leaf-to-stem ratio in crested wheatgrass. Information obtained from this study on agro-morphological traits, nutritive values and ploidy determination among the 45 crested wheatgrass accessions will be useful for future crested wheatgrass breeding programs.