Root Traits, Nodulation and Root Distribution in Soil for Five Wild Lentil Species and Lens culinaris (Medik.) Grown under Well-Watered Conditions

Abstract

The efficient use of resources such as water and nutrients by plants is increasingly important as the world population food demand continues to grow. With the increased production of lentil in the temperate zones of North America, improvement in yield needs to be maintained. The use of wild lentil genotypes as sources of genetic diversity for introgression into cultivated lentil is an important breeding strategy, but little is known about their root systems. We evaluated the root systems of five wild lentil species and Lens culinaris under fully watered conditions. Plants were grown in 60 cm tubes containing equal volumes of soil collected from the reconstructed A, B, and C horizons. Significant differences were observed for root traits and fine root distribution between and within species and the proportion of root biomass partitioned into each soil layer was unique for each genotype. We also observed variability in nodule number and nodule shape within and between genotypes. Some genotypes more efficiently used water for either biomass or seed production. The allocation of resources to seed production also varied between genotypes. These observations could have impact on the design of future lentil breeding in the context of strategies for managing changes in rainfall amount and distribution for lentil production ecosystems.

Keywords: nodules; root distribution; root traits; soil horizons; wild lentil species.

FIGURE 1

Comparison of root dry weight distribution in three soil horizons for five wild lentil genotypes and Lens culinaris Eston. [Bar are standard errors and letters compare root dry weight between genotypes for the same soil horizon; no letters imply similar biomass].

FIGURE 2

Comparing proportions of root (R) to shoot (S) biomass and vegetative biomass (VB) to reproductive biomass (RB) in five wild lentil species to Lens culinaris Eston.

FIGURE 3

Comparison of root trait characteristics in three soil horizons for Lens culinaris Eston and five wild lentil species grown under fully watered conditions. Bars denote standard error. Letters denote significant differences at α = 5% for genotypes in the same soil horizon. (A) TRL, total root length; (B) TRSA, total root surface area; (C) RLD, root length density; (D) MRD, mean root diameter; (E) TRT, total number of root tips; (F) TRF, total number of root forks.

FIGURE 4

Percentage of total root length distribution across six root diameter classes assessed in three soil horizons for seven wild lentil genotypes in comparison to cultivated lentil (Lens culinaris Eston. The line bars are LSD values at P < 0.05 for comparison of genotypes within a diameter class. (A) A horizon; (B) B horizon; (C) C horizon.

FIGURE 5

Percentage of total root surface area distribution for six root diameter classes in three soil horizons for seven wild lentil genotypes in comparison to cultivated lentil (Lens culinaris Eston). The line bars are LSD values at P < 0.05 for comparison of genotypes within a diameter class. (A) A horizon; (B) B horizon; (C) C horizon.

FIGURE 6

Root volume distribution across six diameter classes assessed in three soil horizons in five wild lentil genotypes in comparison with cultivated lentil (Lens culinaris Eston). The line bars represent LSD at P < 0.05 for comparison within a given root diameter class. (A) A horizon; (B) B horizon; (C) C horizon.

FIGURE 7

Variations in nodule shapes found in the root systems of Lens culinaris Eston and seven wild lentil genotypes inoculated with strains of Rhizobium leguminarum (Rhizobium leguminosarum biovar viceae strain 1435; Nodulator XL SCG, Becker Underwood, Canada). (A) L. cul. Eston (B) L. orientalis PI 572376 (C) L. odemensis IG 72623 (D) L. lamottei IG 110813 (E) L. orientalis IG 72643 (F) L. tomentosus IG 72805 (G) L. ervoides L-01-827A (H) L. ervoides IG 72815.