Performance and prediction of potato genotypes tested in international trials

Summary A series of international trials with the potato crop was conducted in eight countries representing widely differing environments. The purpose of the experiments was: (1) to develop a method for obtaining environmental indexes which measure productivity of diverse potato-growing areas, and (2) to construct performance models for individual genotypes based on the environmental indexes. Yield data of 32 genotypes obtained from a series of 13 experiments conducted in the eight countries in 1983 and 1984 were used in the study. The response pattern of the genotypes was studied by a multivariate analysis. Five genotypes were chosen as representatives for different response patterns to the environments and their data were used for calculating a series of independent indexes for each of the experimental sites based on principal component analysis. Performance models for each of the genotypes were constructed by stepwise regression analysis of yields of a genotype on the environmental indexes based on 1983 data. Yield data of 1984 experiments were used to verify the models. Satisfactory correspondence between observed and predicted yields was obtained for most of the genotypes.     

Genetic control over grain damage in a spring barley mapping population

A genetic map was constructed using DNA‐based markers in a barley mapping population derived from the cross ‘Tankard’בLivet’, that was developed to explore the genetic control over grain damage in spring barley cultivars. Quantitative trait loci (QTL) were located for husk skinning, gape between the lemma and palea and splitting of the fused pericarp/testa/aleurone tissues. The QTL accounted for 70% of the genetic variation in Split and 60% of the genetic variation in Gape and Skinning. The QTL were clustered on chromosomes 1H, 4H, 5H, 6H and 7H. QTL analysis indicates the possibility of transgressive segregation for grain splitting and so the breeding of lines with more extreme splitting. This is of concern to the malting industry as, without extensive phenotypic assessment, such lines could be commercialized, as was the case of Landlord, and put malting barley supplies at risk. These findings are discussed in relation to the genetic control over traits including grain length and width.     

Effects of cytoplasm on heterosis and combining ability for agronomic traits in rice (Oryza sativa L.)

Summary Effect of sterilizing (WA) cytoplasm on heterosis and combining ability for days to flowering, plant height and grain yield in rice was studied in 70 crosses and their reciprocals produced by 10 cytoplasmic male sterile (A), their maintainer (B) and seven restorer (R) lines following line x tester design. The materials consisting of 140 hybrids (70 A/R and their reciprocal 70 R/B) plus 17 parental lines (10 B + 7 R) were evaluated under six environments, created by growing in three fields with different fertilizer doses (0, 60, 120 kg N/ha) and 2 seasons (dry and wet) during 1986 at IRRI farm. Reciprocal cross effect (A/R vs R/B) were highly significant for all the three traits. Interaction of reciprocal cross effects with environments were also highly significant for yield and days to flowering. Cytoplasmic effect for yield, days to flowering and plant height were estimated by comparing A/R and R/B combination and testing the significance of difference with LSD value. In order to avoid confounding effect of spikelet sterility on yields, twenty crosses showing normal spikelet fertility were selected. Both positive and negative cytoplasmic effects were observed for the three traits. The effects were modified by environments, except for plant height. Heterosis for all three traits was also affected by cytoplasm, however, manifestation of cytoplasmic effects was higher for heterosis for days to flower than in heterosis for yield and plant height. Effect of cytoplasm was more pronounced on general combining ability effects of parents than specific combining ability effects of crosses. Among the parents two CMS lines A4 (IR54752A) and A8 (IR22107-113-3-3A) and two R lines: R2 (IR46) and R7 (IR9761-19-1) showed consistent positive effect of cytoplasm on general combining ability. These lines have given several good heterotic combinations. The study indicated the usefulness of evaluating diverse cytoplasmic sources in various nuclear genotypes bred for hybrid rice breeding program.     

QTL mapping and associated marker selection for the efficacy of green plant regeneration in anther culture of rice

Anther culturability of rice is a quantitative trait controlled by nuclear‐encoded genes. The identification of quantitative trait loci (QTL) and associated marker selection for anther culturability is important for increasing the efficiency of green plant regeneration from microspores. QTL associated with the capacity for green plant regeneration in anther culture of rice were mapped on chromosomes 3 and 10 using 164 recombinant inbred (RI) lines from a cross between ‘Milyang 23’ and ‘Gihobyeo’. The quantitative trait locus located on chromosome 10 was detected repeatedly when three anther culture methods were applied and was tightly linked to the markers, RG323, RG241 and RZ400. Associations between these markers and the efficacy of green plant regeneration in 43 rice cultivars and two F₂ populations, ‘MG RI036’/‘Milyang 23’, and ‘MG RI036’;/‘IR 36’ were analysed. One of these markers, RZ400, was able to identify effectively genotypes with good (> 10.0%) and poor (< 3.0%) regenerability, based on the marker genotypes in the cultivars and two F₂ populations. This marker enables the screening of rice germplasm for anther culturability and introgression into elite lines in breeding programmes.     

Grain-yield characteristics of oat lines surviving uniform and shuttle selection strategies

Summary Four selection strategies were used on four sets of oat lines to select for grain yield. Two of these used uniform environments whereby sequential selection of the high-yielding lines occurred in continuous high- or continuous low-productivity environments. These are referred to as high and low uniform selection strategies, respectively. The other two selection strategies were conducted by sequential selection of the high-yielding lines in alternating high- and low-productivity environments. They are referred to as high and low shuttle selection strategies, respectively, with high and low designating the productivity of the first environment in the sequence. After three or four cycles of selection, the surviving lines and a random sample from each set were evaluated for mean grain yield, grain yield response to improving environments, and stability of grain yield, in a range of environments typical of oat production on Iowa farms.Grain yield and regression response for all selection strategies, when calculated across all sets of lines, were significantly greater than corresponding values for random samples. Stability was unchanged. The uniform-high and uniform-low strategies gave the greatest and the smallest gains in mean grain yield, respectively, with the shuttle strategies giving intermediate gains. Shuttle selection in predominantly high-productivity environments increased grain yield more than shuttle selection in predominantly low-productivity environments. The uniform-strategy followed by the shuttle-high strategy identified entries with superior performance in high productivity environments. Increased gain in mean grain yield across all environments was associated with increased number of selection cycles conducted in high-productivity environments.Journal Paper No. J-15252 of the Iowa Agric. and Home Econ. Exp. Stn., Ames, Iowa 50011, USA. Project No. 2447.     

Effects of protein and peptide addition on lipid oxidation in powder model system

The effect of protein and peptide addition on the oxidation of eicosapentaenoic acid ethyl ester (EPE) encapsulated by maltodextrin (MD) was investigated. The encapsulated lipid (powder lipid) was prepared in two steps, i.e., mixing of EPE with MD solutions (+/- protein and peptides) to produce emulsions and freeze-drying of the resultant emulsions. EPE oxidation in MD powder progressed more rapidly in the humid state [relative humidity (RH) = 70%] than in the dry state (RH = 10%). The addition of soy protein, soy peptide, and gelatin peptides improved the oxidation stability of EPE encapsulated by MD, and the inhibition of lipid oxidation by the protein and the peptides was more dramatic in the humid state. Especially, the oxidation of EPE was almost perfectly suppressed when the lipid was encapsulated with MD + soy peptide during storage in the humid state for 7 days. Several physical properties such as the lipid particle size of the emulsions, the fraction of nonencapsulated lipids, scanning electron microscopy images of powder lipids, and the mobility of the MD matrix were investigated to find the modification of encapsulation behavior by the addition of the protein and peptides, but no significant change was observed. On the other hand, the protein and peptides exhibited a strong radical scavenging activity in the powder systems as well as in the solution systems. These results suggest that a chemical mechanism such as radical scavenging ability plays an important role in the suppression of EPE oxidation in MD powder by soy proteins, soy peptides, and gelatin peptides.     

Selection of Tolerant Plants and Their Arrangement to Restore a Forest Ecosystem Damaged by Air Pollution

Plants tolerant to polluted environments were selected, based on several criteria, to restore a coastal forest ecosystem severely damaged by air pollutants discharged from an industrial complex. In addition, a restoration plan was prepared synthesizing these results and the diagnostic ecological indicators in the area for which restoration is required. Pollution-tolerant plants of 11 tree and subtree species, 10 herb species and one shrub species were selected from field surveys in the vicinity of two representative industrial complexes in Korea, Ulsan and Yeocheon. Nine species were selected for tolerance to SO₂ fumigation and six species were selected for tolerance to Al³⁺. Growth and photosynthetic responses of sample plants transplanted into polluted and unpolluted sites showed that 15 species out of the 26 sample plants showed a disposition for tolerance. Most of these are endemic plants and they are composed of diverse species in structure and function. This result implies that these tolerant species could play important roles in the restoration of the study area, which has several specific features. On the other hand, results from transplant tests indicate that a field survey is the most reasonable method for selection of tolerant plants to restore a pollution-damaged ecosystem, as was shown in another restoration program. Results of ecological analysis on vegetation map indicate that the spatial range within the first ridge is the sector for which restoration is required. This sector was classified into four zones on the basis of topographic conditions: lower and upper slopes of both slopes facing and opposite the pollution source. Guidelines for soil amelioration and arrangement of tolerant plants were prepared considering the degree of vegetation degradation, leaf damage of major plant species and soil pollution in each zone under the restoration plan.     

Lepidium latifolium: plant nutrient competition-soil interactions

Exotic weeds are invading rangelands of the western United States at unprecedented rates. Understanding plant-soil relationships and competitive interactions of invasive weeds is crucial in long-term control strategies. In a greenhouse experiment, we investigated the influence of soil nutrient depletion on plant growth and plant competition between the exotic invasive weeds, Lepidium latifolium (invading wetlands) and Bromus tectorum (invading a multitude of habitats). Plants were grown individually and in combination until L. latifolium flowered, then roots and aboveground mass were harvested. Soil in individual pots was homogenized, subsamples collected for nutrient analyses, and the soil was re-planted to the same species, grown, and harvested twice more for a total of three growth cycles. As nutrient supplying capacity of the soil declined through growth cycles, aboveground mass of L. latifolium decreased significantly (PА.05) and growth potential of B. tectorum surpassed that of L. latifolium. Only bicarbonate-extractable soil ortho-P positively correlated with plant mass of L. latifolium. A separate experiment demonstrated that L. latifolium has a narrow window of soil water potentials for optimal growth; greatest growth at -20 kPa with significantly declining growth at saturation and -400 kPa. Our data suggest that L. latifolium primarily invades wetlands because the high soil water content reduces tortuosity and allows efficient transport of nutrients to this sparsely rooted species. When soil moisture and/or the nutrient supplying capacity of the soil declines, plants with greater root density can out-compete L. latifolium. Monocultural stands of L. latifolium may be self-limiting in time as available nutrients, particularly P, are biocycled to drier upper soil layers.     

Erythritol attenuates the diabetic oxidative stress through modulating glucose metabolism and lipid peroxidation in streptozotocin-induced diabetic rats

We investigated the effects of erythritol on rats with streptozotocin- (STZ-) induced diabetes mellitus. Oral administration of erythritol [100, 200, or 400 mg (kg body weight)(-1) day(-1) for 10 days] to rats with STZ-induced diabetes resulted in significant decreases in the glucose levels of serum, liver, and kidney. Erythritol also reduced the elevated serum 5-hydroxymethylfurfural level that is glycosylated with protein as an indicator of oxidative stress. In addition, thiobarbituric acid-reactive substance levels of serum and liver and kidney mitochondria were dose-dependently lower in the erythritol-treated groups than in the control diabetic group. Furthermore, the serum creatinine level was reduced by oral administration of erythritol in a dose-dependent manner. These results suggest that erythritol affects glucose metabolism and reduces lipid peroxidation, thereby improving the damage caused by oxidative stress involved in the pathogenesis of diabetes.