The effects of ploidy and a phenotype conferring a high water-soluble carbohydrate concentration on carbohydrate accumulation, nutritive value and morphology of perennial ryegrass (Lolium perenne L.)

Abstract

Smith, K. F., Simpson, R. J., Culvenor, R. A., Oram, R. N., Humphreys, M. O., Prud'homme, M. P. (2001). The effects of ploidy and a phenotype conferring a high water-soluble carbohydrate concentration on carbohydrate accumulation, nutritive value and morphology of perennial ryegrass (Lolium perenne L.). Journal of Agricultural Science, 136, 65-74.Tetraploidy or the use of diploid genotypes with genes conferring high water-soluble carbohydrate concentrations are two mechanisms to increase the nutritive value of perennial ryegrass. This experiment compared the morphology, nutritive value and diurnal variation in water-soluble carbohydrate (WSC) concentrations of 56-day-old plants from six perennial ryegrass cultivars grown under controlled environment conditions. Three of these cultivars were diploid (Melle, Aurora and Cariad) and three were tetraploids (Meltra, Prospero and AberOnyx) which had been derived from the respective diploid cultivars. Two of the diploid cultivars (Cariad and Aurora) had previously been selected for high concentrations of water-soluble carbohydrates. The tetraploid cultivars had fewer (mean 59), larger tillers than the diploids (mean 83). However, with the exception of Melle and Meltra the dry matter yield of the diploid cultivars was not significantly different from their tetraploid derivatives. The effect of tetraploidy on WSC concentrations was dependent on the genetic background of the cultivars. Melle, which had not been previously selected for increased WSC, had a significantly lower WSC concentration than its tetraploid derivative, Meltra. However, tetraploidy did not further increase the WSC concentration in those cultivars previously selected for high WSC concentrations. WSC concentrations in the leaf of both Aurora and Melle rose by 65?70 g/kg throughout the photoperiod, suggesting that differences in the total WSC concentration of these cultivars were not due to any increase in the amount of carbon fixed by Aurora but rather due to differences in the allocation of carbon during growth and development. This experiment demonstrated that tetraploidy was not beneficial in improving the WSC concentration of perennial ryegrass when imposed on two diploid cultivars which had the genetic potential for increased WSC accumulation. However, tetraploidy significantly increased the WSC concentration and by implication the nutritive value of a cultivar derived from a perennial ryegrass cultivar with standard WSC concentrations.Peer reviewe

The effects of ploidy and seed mass on the emergence and early vigour of perennial ryegrass (Lolium perenne L.) cultivars

“…The results obtained in this experiment were consistent with those obtained with mature perennial ryegrass plants (Neuteboom et al 1988;Smith et al 2001) or with seedlings of other species (Berdahl and Rees 1997), with tetraploid plants tending to have fewer tillers and larger leaves than diploid plants.…”

“…In nature, the species exists as a diploid (2n = 2x = 14); however, it is possible to induce tetraploidy (2n = 4x = 28) in perennial ryegrass through the use of colchicine (Morgan 1976). The induction of tetraploidy in perennial ryegrasses leads to changes in the morphology of plants, such as increased seed mass (Sugiyama 1998), increased cell size (Wilkins and Sabanci 1990), increases in the size of leaves and tillers (Neuteboom et al 1988;Smith et al 2001) and a decrease in the rate of leaf and tiller appearance (Neuteboom et al 1988;Smith et al 2001).…”

“…Tetraploid cultivars of perennial ryegrass are not widely sown in Australia, although with several cultivars commercially available their use is likely to increase, as it has done in Europe where tetraploid cultivars are widely sown due to their generally higher forage quality than that of diploids (Castle and Watson 1971;Smith et al 2001). These increases in forage quality have led to increases in milk (Castle and Watson 1971) and meat production (Vipond et al 1993(Vipond et al , 1997 when combined with appropriate grazing management.…”

Environmental and Genetic Variation for Water Soluble Carbohydrate Content in Cool Season Forage Grasses

“…A variation of 20% for WSC concentration among six diploid ryegrasses was found to be consistent over several years (Smit, 2006), the largest variation among cultivars was found during summer, in July and August. Tetraploid cultivars generally had a higher WSC concentration than diploid cultivars (Smith et al 2001;Gilliland et al 2002). DMD concentration declined during summer due to the influence of higher temperatures, however, high WSC lines exhibited fewer declines in DMD than the lines that did not accumulate as much WSC.…”

Características produtivas e morfofisiológicas de cultivares de azevém

“…A duplicação de cromossomos afeta, diretamente, o desempenho da planta, devido ao aumento no volume celular (Balocchi & López 2009). Com isto, o teor de água se eleva, assim como os teores de carboidratos solúveis, proteínas e lipídios, aumentando a digestibilidade, eficiência ruminal e desempenho animal (Smith et al 2001, Nair 2004.…”