Changes in Root Architecture and Aboveground Traits of Red Clover Cultivars Driven by Breeding to Improve Persistence

Abstract

Red clover persistence has been one of the major targets for the most breeding programs worldwide. A phenotypic characterization at above- and belowground level was performed to a set of highly persistent red clover populations. The objective was to identify phenotypic changes occurring after empirical selection for plant survival, which is the consensus criteria of persistence. Eleven red clover populations were established on mesocosms of polyvinyl chloride (PVC) tubes of 11 cm in diameter and 100 cm depth, containing as substrate a mixture (v/v) of sand, vermiculite, soil and perlite. The trial was organized in a randomized complete block design with four replicates, each replicate consisting of five mesocosms per population and one plant per mesocosm. In total, 220 mesocosms were handled. At aboveground level, growth parameters, specific leaf area (SLA) and shoot dry matter (ShootDM) were measured. At belowground level, root morphology (volume, diameter and length) and topology (altitude, external path length [EPL] and dichotomous branching index [DBI]) were measured through image analyses. Analyses of variance were performed implementing a phenotypic linear mixed model using the Restricted Maximum Likelihood method. Additionally, variance components were estimated and broad-sense heritability was calculated for each phenotypic trait. Highly persistent cultivars exhibited 30% higher ShootDM and 10% lower leaf size and SLA than the oldest low-persistent cultivar Quiñequeli. At root level, they showed 20, 50 and 50% higher crown diameter, root length density and root volume than Quiñequeli, respectively, but 20% lower DBI. Root traits exhibited medium-low values of genetic control; broad sense heritability ranged between 0.20 and 0.48. In conclusion, highly persistent red clover cultivars and experimental lines bred in Chile modified their phenotypic expression of individual plants at shoot and root levels relative to the oldest low persistent cultivar Quiñequeli. Associations among above- and belowground traits offer opportunities for designing more efficient selection strategies. For instance, the strong relationship between SLA and root traits offers tremendous potential for indirect phenotypic selection.

Root system architecture and environmental flux analysis in mature crops using 3D root mesocosms

“…Root mesocosms, typically large horticultural pots or long narrow pipes form which the entire root system can be extracted, have proven useful in understanding RSA and root function of several agricultural species. For examples: it was reported that a lower number of crown roots in maize can be beneficial for nitrogen acquisition in poor nitrogen soils ( Saengwilai et al., 2014 ), a moderate progressive drought could lead to RSA adaptations in various rice cultivars that improve performance under reduced water management practices ( Hazman and Brown, 2018 ), some Green Revolution wheat progenitors have smaller root systems than older landraces ( Waines and Ehdaie, 2007 ), and Chilean red clover cultivars with certain RSA traits, such as high crown root diameter and low branching index, correlate with superior persistence ( Inostroza et al., 2020 ). However, in these studies the root systems were physically constrained during growth, leading to, at minimum, compromised estimates of root length densities and other metrics across the depth profile.…”

Phenotypic Diversity and Productivity of Medicago sativa Subspecies from Drought-Prone Environments in Mediterranean Type Climates

“…This insight could be considered as empirical evidence of the drought tolerance improvement transferred from M. arborea to M. sativa . Tani et al [ 18 ], showed that at seedling stage, alborea hybrids exhibited higher stem elongation rate, photosynthetic rate, stomatal conductance, and transpiration rate (E) than sativa and arborea accessions under drought stress, indicating that the hybrids correspond to a drought tolerance ideotype [ 30 , 31 , 32 , 33 , 34 , 35 ].…”

“…Additionally, ShootDM (an estimator of forage yield) forage yield was significantly associated with SLA, leaf size and StemD, which coincide with results of other works [ 36 ]. From an agronomic point of view, the alfalfa LSratio has been used as a positive estimator of forage quality, owing to the greater quality of leaves relative to stems [ 32 , 37 , 38 ]. The LSratio performed as a differentiator trait of the agronomic categories identified by the cluster analysis.…”

Morpho‐physiological changes induced by soil environment modulate the compatibility of perennial ryegrass and white clover cultivars

“…In SSS, the mixed sward increased its RDW accumulation and RLD during the entire growing season, relative to DSS (Figure 1; Table 4). This is a common response of plants growing under marginal soil conditions to increase the soil foraging capacity and capture of soil resources (Acuña et al., 2016; Acuña & Inostroza, 2013; Inostroza et al., 2020; Inostroza, Acuña & Méndez, 2015 ; Inostroza & Acuña, 2010; Lynch, 2019). Inostroza et al.…”

“…Additionally, RLD is narrowly related with root diameter. Greater RLD species tend to have greater plasticity in root growth and greater physiological capacity for water and nutrient uptake (Fitter, 2002; Inostroza et al., 2020).…”