Genetic Diversity of Diurnal Carbohydrate Accumulation in White Clover (Trifolium repens L.)

Abstract

White clover (Trifolium repens L.) is one of the most important legumes for fodder production in temperate climates, particularly in intensive pasture systems. Like many other forage legumes, it lacks the energy content to maximize productivity of modern ruminant livestock breeds. White clover produces water-soluble carbohydrates and starch in its leaves as a diurnal product of photosynthesis. However, little is known about the genetically encoded variability of diel changes in carbohydrate content. We assessed the amount of glucose, fructose, sucrose, and starch in the leaves of 185 plants of a genetically diverse white clover population. Water-soluble carbohydrates only provided on average 10.6% of dry weight (DW) of the total analyzed non-structural carbohydrate (NSC) content at the end of the day (ED), while starch supplied 89.4% of the NSC content. The top 5% of individuals accumulated over 25% of their DW as starch at ED. The leaf starch content at ED showed up to a threefold difference between genotypes, with a repeatability value of 0.95. Our experiments illustrate both the physical potential of white clover to serve as a competitive energy source to meet the demand of modern ruminant livestock production and the genetic potential to improve this trait by breeding. these systems are economically less competitive with CFOs in terms of energy supply [4]. For most animal diets, energy is primarily derived from non-structural carbohydrates (NSCs), which are differentiated from structural carbohydrates that form dietary fiber. NSCs can be further distinguished into water-soluble carbohydrates (WSCs) and starch. In maize and other cereal grains, 70-80% of the grain dry weight (DW) is starch [5].In pasture and grassland systems, NSC content is determined by seasonal and diurnal accumulation of metabolites. Starch and many WSCs are products of photosynthesis that accumulate in the leaves of plants during the day [6]. These NSCs are mobilized at night to facilitate growth and respiration [7]. In perennial ryegrass (Lolium perenne L.), the WSC content is primarily derived from soluble fructans stored in the vacuoles of stems and leaves, which can reach 20-25% of the dry matter [8,9]. In forage legumes, the major WSCs are glucose, fructose, and sucrose, but osmolytes such as pinitol can become a major fraction during stress [10][11][12]. Starch can make up 25-35% of the DW biomass in some forage legumes such as red clover (Trifolium pretense L.) and alfalfa (Medicago sativa L.). Because starch is a product closely linked to photosynthesis, this accumulation is highly dependent on environmental factors such as light intensity, harvest time, temperature, and day length [13,14]. At night, starch mobilization in white clover (T. repens L.) is reduced under low temperatures and starch accumulates [15].Because of the high degree at which both WSC and starch contents are influenced by the environment, such contents have been elusive for breeders of forage crops to select. The WSC content in perennial ryegrass is influenced...

Isoflavone supplementation, via red clover hay, alters the rumen microbial community and promotes weight gain of steers grazing mixed grass pastures

“…Previous results showed that biochanin A inhibited amylolytic bacteria, including Streptococcus bovis [8]. Typical forage legumes, like clovers, contain variable amounts of starch [41]. In C3 grasses, starch tends to be a smaller proportion of the nonstructural carbohydrate than fructan [42], although starch concentrations can be elevated at low temperatures [43].…”

Starch Trek: The Search for Yield

“…It has been known for many years that increasing AGPase activity leads to increased starch synthesis, and as was mentioned above, increasing starch in food and fodder crops would improve their calorific value (Ruckle et al., 2017, 2018). However, interestingly, increasing starch amounts in this way can have beneficial effects on plant productivity.…”

“…Unfortunately, although this was demonstrated convincingly in glasshouse trials (Ral et al., 2012; Bowerman et al., 2016), when the same lines were examined in the field a reduction in yield was observed (Whan et al., 2017). Although it may not be a valuable way to increase starch yield in storage organs, repressing genes involved in this process could improve forage and silage crops by improving their calorific value for animal feed (Weise et al., 2012; Ruckle et al., 2018).…”

Rethinking temperature effects on leaf growth, gene expression and metabolism: Diel variation matters

“…Starch, sucrose, fructose and glucose contents were quantified as described in earlier studies (Ruckle et al, 2017 ; Ruckle, Bernasconi, Kölliker, Zeeman, & Studer, 2018 ). The flash‐frozen samples (see above) were lyophilized, and biomass was recorded as lyophilized leaf weight.…”