Improving environmental benefits of white clover through condensed tannin expression

Abstract

<jats:p>Forage legumes improve both the intake and quality of the diet in pasture-based livestock systems. However, the high protein content of these forages can lead to inefficient nitrogen utilisation in the rumen and to high nitrogen (N) losses in urine and dung. Condensed tannins in forages have been shown to significantly reduce N leaching and also methane emissions. The use of classical breeding approaches over more than 50 years has failed to elevate condensed tannins in forage legumes. However, molecular biology approaches have achieved condensed tannin expression in white clover at levels that are biologically significant (&gt;2% of dry matter). Results from a field trial in the USA showed that while condensed tannin levels in white clover (Trifolium repens) were similar to those produced by birdsfoot trefoil (Lotus corniculatus), plants did suffer a yield penalty. Protein binding assays were conducted by incubating soluble white clover leaf CTs in a solution containing the protein bovine serum albumin (BSA). The CTs in white clover leaves efficiently precipitated BSA from the supernatant at pH 6.5, and these CT-protein complexes dissociated at pH 2.5.While the use of genetically modified organisms in New Zealand is regulated, this development has the potential to improve environmental, animal health and animal productivity outcomes from grazed pasture systems.</jats:p>

Large Inter- and Intraspecies Variability of Polyphenols and Proanthocyanidins in Eight Temperate Forage Species Indicates Potential for Their Exploitation as Nutraceuticals

“…However, increase in floral PA concentration and higher flower density led to a decrease in white clover persistence and agronomic performance in the fields. The results from that study suggested that future research should focus on modulating PA expression in white clover leaves, which can concomitantly maintain their agronomic performance in the field. , …”

The hunt for the “holy grail”: Condensed tannins in the perennial forage legume white clover (Trifolium repens L.)

“…Progenies of genetically engineered white clover containing a TaMYB14‐1 transcription factor from Trifolium arvense (Hancock et al, 2012) were produced in another study as described by Roldan et al (2022) and Woodfield et al (2019). Briefly, agrobacterium‐mediated transformation was used to transfer the binary vector into the commercial white clover cultivar Mainstay.…”

“…In 2017 seed from backcrosses (BC 1 ) between a transgenic parent and a cultivar Mainstay genotype (2 families each for CTB and CTG event and 1 family for CTF) were grown. In 2018, the BC 2 & T 2 progeny from backcrosses (BC 2 ) (1 each of CTB, CTF and CTG) and T 2 (1 each of CTB & CTG) families were grown (Woodfield et al, 2019).…”

“…In this study, the plant traits involved only the 2019 data which included leaf width, leaf length, petiole length, stolon diameter, plant height and dry herbage yield (plants were harvested at 5 cm from ground). The plant traits from previous field trials were covered in Woodfield et al (2019). To evaluate enhancement in mean soluble CTs within 3 generations, the mean CTs in the leaves of 2019 plants were plotted with mean CTs obtained in 2017 and 2018, and the mean CTs per family from plants grown in the field trial (USA) were plotted against the mean CTs of the same family grown under glasshouse condition in New Zealand.…”

Plant breeding for resilient pastures

“…In legumes, the aim to deliver condensed tannin expression in leaves of white clover and lucerne has been achieved through using a single gene transformation (Hancock et al 2012(Hancock et al , 2014. Condensed tannins in forages, through binding protein, can significantly reduce N leaching and also methane emissions (Woodfield et al 2019). A scenario for achieving co-existence of genetically modified (GM) and non-GM crops and pastures has been proposed to stimulate discussion (Rolleston 2016).…”