Search

Breeding cool-season (C3) grasses with higher magnesium (Mg) content is a promising attempt for reducing grass tetany hazard in ruminants. Faster methods for plant mineral analyses could increase the number of individual plants screened for higher Mg content (High-Mg). This study evaluates the effectiveness of energy dispersive X-ray microanalysis (EDX) as well as energy reflectance X-ray spectrometry (XRF) for screening high-Mg grass genotypes. The approach was verified by using two tall fescue cultivars having known differences in magnesium (Mg) content, viz. HiMag (high-Mg cultivar) and Ky-31 (control cultivar). We assumed that cultivars with known variation in Mg concentrations could provide a test for the applicability of the new methodology in finding naturally occurring high and low Mg containing grass genotypes. Plants samples included a population of 8 plants consisting of four harvests for three years and were analyzed for Mg, calcium (Ca), and potassium (K) by EDX and ERF, and data were verified with atomic absorption spectrometry wet (AAS). While observing the frequency distribution for different nutrient concentrations, HiMag tall fescue showed higher Mg and lower K concentrations than that of Ky-31. There was positive linear relationship between AAS and EDX estimated Mg, Ca and K (r = 0.88, 0.62 and 0.89, respectively), indicating close agreement between AAS and EDX estimation. Also, there was a positive linear relationship between AAS and XRF, as the r values were 0.87, 0.65 and 0.88 for Mg, Ca, and K, respectively. The tetany ration was established for EDX and XRF and the results were dependable with wet chemistry. [ABSTRACT FROM AUTHOR]

An experiment was conducted to evaluate the effect of endophyte Neotyphodium coenophialum (Morgan-Jones and Gams) Glenn, Bacon, and Hanlin on the mineral content of tall fescue (Lolium arundinaceum Schreb., SJ Darbyshire) ecotypes (Fukaura, Koiwai, and Showa) grown on two Andisols (Black Andisol and Red Andisol) with different fertilities. Black Andisol, with a naturally low content of phosphorus, was high in other nutrients, while Red Andisol, with a naturally high content of phosphorus, was low in other nutrients. Shoot dry weight was significantly higher in endophyte-infected (E+) than endophyte-free (E-) plants grown in Black Andisol. On the other hand, in Red Andisol, only Fukaura showed higher shoot dry matter production in E+ plants as compared to E- plants. In general, greater concentrations of phosphorus and manganese were found in endophyte-infected (E+) plants than non-infected (E-) plants. Accumulation of all nutrients in E+ plants was remarkably higher than in E- plants. Excluding the plant ecotype effect, the nutrient concentration and accumulation pattern for plants in the two soils was different in E+ and E- plants. Plants growing in Black Andisol had greater concentrations of phosphorus (P), copper (Cu), and zinc (Zn) in E+ plants than those of E- plants whereas for plants in Red Andisol the reverse was true. Significantly higher concentration of manganese (Mn) was found in E+ plants irrespective of soils. Regardless of endophyte and ecotypes, plants grown in Black Andisol showed significantly higher values for both nutrient concentration and accumulation than those in Red Andisol. Apart from the plant ecotype Showa, all other ecotypes had the greatest accumulation and concentration of phosphorus in E+ plants. In two types of soil and among the three plant ecotypes, endophyte infection had different effects on nutrients acquisition. Giving emphasis on nutrient accumulation, endophyte played an overall negative role on plants grown in Red Andisol. There may be a metabolic cost of harboring endophytes offset its benefit in Red Andisol. Since the same species of endophyte infected all three ecotypes, our results show that the host/endophyte interaction depends on plant ecotype as well as the ability of the soil to supply nutrients. [ABSTRACT FROM AUTHOR]

Neotyphodium coenophialuminteracts mutualistically with its host grasses. Tall fescue (Festuca arundinaceaSchreb.) plants infected by the fungal endophyte,Neotyphodium coenophialum(Morgan-Jones and Gams) Glenn, Bacon and Hanlin, often perform better than non-infected plants, especially in limited resource environments. However, there is a scarcity of information about endophyte-grass ecotypes interaction in Andisols of temperate regions. Clones of three tall fescue ecotypes (Fukaura, Koiwai and Showa) either infected withN. coenophialum(E+) or noninfected (E-) were grown in Andisols (Black Andisol: naturally low content of phosphorus, high in other nutrients; Red Andisol: naturally high content of phosphorus, low in other nutrients) for 133 days in a controlled environment. Cumulative shoot dry weight, daily regrowth rates (tiller number, plant height and shoot dry matter) after clippings and nutrient uptake, transport and efficiency ratios were measured. In Black Andisol, E+ plants had significantly higher cumulative shoot dry weight as well as daily regrowth rates than E- plants, while in Red Andisol the reverse was true. Among the ecotypes studied, Showa had the highest shoot growth. Significantly higher phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) uptake as well as transport were identified in E+ vs. E- plants grown in Black Andisol. With few exceptions, values for nutrient efficiency ratios were not significantly different between E+ and E- plants grown in both soils. Significant three-way interaction (endophyte × ecotype × soil) for cumulative shoot dry weight and regrowth rate revealed that the ecotype specific regrowth responses to endophyte infection were depended on soil nutrient conditions. Vegetative growth and nutrient acquisition in tall fescue varied with ecotype and were modified by abiotic (soil fertility status) as well as biotic (endophyte infection) factors. [ABSTRACT FROM AUTHOR]

There is a continued need for breeding high-Mg grass cultivars with low grass tetany risk. Since interaction between magnesium (Mg) and potassium (K) exists, there is a possibility that genotypes characterized for higher Mg concentration may exhibit contrasting behavior for nutrient uptake with K application. A solution culture experiment was conducted to find a suitable K level for individual selection of high-Mg plants. Three K treatments of 1.0, 5.0, and 25 mM were superimposed. The uptake pattern of Mg, calcium (Ca), and K for approved high-Mg cultivars of Italian ryegrass (Magnet), orchardgrass (Mgwell), and tall fescue (HiMag) were compared with that of control cultivars. The seedlings were evaluated for shoot dry weight, amount of nutrient uptake, and average shoot nutrient concentrations. There was an increase in shoot dry weight grown with higher nutrient solution K levels. The effect of K on the trend of Mg uptake was paralleled among the high-Mg cultivars of the three species. The high-Mg cultivars showed higher Mg uptake and average shoot Mg concentrations than the control cultivars. Potassium uptake and average shoot K concentrations of high-Mg cultivars was always lower than the control cultivars. The greatest difference between the controls and high-Mg plants for average shoot Mg and K concentrations was observed in the plants grown under 5.0 mM level of K. This indicates the effectiveness of screening high-Mg grass seedlings using 5.0 mM level of K under solution culture condition. Methodology introduced in this experiment is aimed at expediting the term necessary for screening high-Mg plants. [ABSTRACT FROM AUTHOR]

Breeding for high magnesium (Mg) concentrations has been conducted for several forage species. Mgwell, Magnet, and HiMag are the first experimental strains, bred for increased Mg concentrations of orchardgrass, Italian ryegrass, and tall fescue, respectively. This experiment compared the performance and genetic variability of these high-Mg cultivars grown in solution culture with other cultivars in each species. Three mineral absorption experiments were carried out with one month aged seedlings. Seedlings were evaluated for shoot dry weight, uptake and concentration of Mg, calcium (Ca), and potassium (K), and also the density of these minerals in the shoot. The cultivars of different species behaved differently among the experiments even though the over all environmental condition was kept similar. The high-Mg cultivars showed higher Mg uptake per plant, but the differences were not so distinct. However, the trend in Mg concentration among the cultivars of different species was similar, and the difference between high-Mg cultivars and control cultivars was distinct. The Mg density in the shoot of these cultivars was significantly high. Also the high-Mg cultivars showed lower equivalent ratio, K/(Ca + Mg). Genotypic differences in high-Mg cultivars with others could be distinctly explained by differences in Mg concentration and Mg density in the shoot, which coupled with low K/(Ca + Mg) ratio. These common properties of high-Mg cultivars might be considered as a good parameter for screening. [ABSTRACT FROM AUTHOR]