The constraints imposed by the requirement of acceptable malting and brewing quality in new barley(Hordeum vulgare L.) cultivars, and the resultant use of a narrow germplasm base make the genetic gains in breeding of Midwestern malting barleys of special interest. In this study cultivars which have dominated the malting barley acreage in the tri‐state area of Minnesota and North and South Dakota since 1920 were evaluated to determine the amount of genetic gain which has been made in yield, agronomic and quality traits. Six cultivars were evaluated for 18 traits in seven trials conducted at Crookston and St. Paul, Minn. during the years 1978 to 1982. Four of the six cultivars—‘Kindred’ ‘Traill,’ ‘Larker,’ and ‘Morex’—were in turn the dominant cultivar in the tri‐state malting barley area. Cultivars differed significantly for 15 of the 18 traits. Grain yield of Morex was 51% greater than that of ‘Manchuria,’ the oldest cultivar; the average annual increase in grain yield measured from Manchuria to Morex was 0.9%. However, regression analysis indicates that for the past 40 years, the time period in which serious breeding efforts have been made in the tri‐state area, yield gains have been nearly linear with an average annual increase of 2%.During this time grower yields have nearly doubled and 73% of this increase can be attributed to improved cultivars or genetic improvement. Increases in grain yield of the cultivars were attributed to improvements in lodging resistance, an increase in harvest index( HI) from 0.31 to 0.40, and increases kernel weight and spike number. Significant improvements were achieved for plump kernels, malt extract, alpha amylase, diastatic power and disease resistance. Nitrogen harvest index also was higher in the newer cultivars. The results indicate that sizable yield gains, as well as gains for other traits, can be made within a relatively narrow germplasm base.
Recombinant inbred lines (RILs) derived from B73 ϫ M017 were screened for cold germination (CG) and desiccation tolerance (DT) phenotypes. Reciprocal F 1 hybrids were made between divergent RILs, and hybrids that showed differential phenotypes (parent-of-origin effect) for CG or DT were selected for profiling mRNA and protein expression. mRNA and proteins were extracted from embryo axes of seed germinated for 11 d at 12.5°C in the dark and developing embryos at 40% seed moisture (R5 stage) for CG and DT, respectively. GeneCalling analysis, an open-ended mRNA profiling method, identified 336 of 32,496 and 656 of 32,940 cDNA fragments that showed Ն1.5-fold change in expression between the reciprocal F 1 hybrids for CG and DT, respectively. Protein expression map (PEM) analysis, an open-ended two-dimensional polyacrylamide gel electrophoresis, identified 117 of 2,641 and 205 of 1,876 detected proteins to be differentially expressed with Ն1.5-fold change between the reciprocal F 1 hybrids in CG and DT samples, respectively. A subset of these proteins was identified by tandem mass spectrometry followed by database query of the spectra. The differentially expressed genes/ proteins were classified into various functional groups including carbohydrate and amino acid metabolism, ion transporters, stress and defense response, polyamine metabolism, chaperonins, cytoskeleton associated, etc. Phenotypic analysis of seed from self-pollinated ears of the reciprocal F 1 hybrids displayed small differences compared with the reciprocal hybrids themselves, suggesting a negligible effect of cytoplasmic factors on CG and DT traits. The results provide leads to improving our understanding of the genes involved in stress response during seed maturation and germination.
Field experiments were conducted in 1979 and 1980 to identify visual indicators that coincide with physiological maturity (PM) and 95% maximum kernel dry weight (95% MKW) in hard red spring wheat (Triticum aestivum L.). Dates of PM and 95% MKW were calculated from polynomial regression equations fitted to dry weight accumulation data from eight genotypes differing in several agronomic traits. In 1980, kernels were divided into three groups according to their position on the spike (bottom, middle, and top) to determine the order in which kernels achieve their maximum dry weight.The mean number of days from anthesis to 95% MKW and PM ranged from 22.3 to 33.7 and 27.9 to 40.1, respectively, depending upon planting date and genotype. Kernels matured, in order, from the top of the spike down. The time of 95% MKW preceded PM by about 7 days. Of the 13 visual characteristics observed during the grain‐filling period, first appearance of the pigment strand in the crease most closely coincided with the calculated date of PM. Complete loss of green color from the glumes also occurred close to PM. Complete loss of green color from the flag leaf most consistently coincided with the time of 95% MKW. An abrupt drop in kernel moisture content also occurred at 95% MKW. Complete loss of green color from the flag leaf could, therefore, be used as an indicator of the commencement of rapid kernel dry‐down and the final stage of grain filling which ends when the pigment strand is first visible and the glumes have lost all green color. Kernel moisture percentage at PM and 95% MKW was too variable to be considered a reliable indicator of either PM or 95% MKW.
Increased crop yields over the past 50 to 100 years have been attributed to new cuitivars and improved cultural and management practices. Documentation of the contribution of plant breeding to oat (Avena sativa L.) yield improvement may provide insights into the optimum strategy for attaining further gains. Our objective was to quantify genetic improvements in grain yield, kernel quality, and associated agronomic and physiological traits of oat cnltivars grown in Minnesota over the past six decades. Nine cultivars released since 1923 were grown in field experiments at St. Paul, Minn. in 1979 to 1981. Mean grain yield over all years ranged from 20.0 q/ha for 'Anthony', to 31.3 q/ ha for 'Moore'. Based on the mean yield of 'Gopher', the annual rate of increase since 1923 was 0.8%. Newer cultivars generally lodged less than older cultivars, which may also contribute to the increases in harvestable grain yield obtained in commercial fields today. Cultivars differed in groat percentage, but no trend with time of release was evident. The collective improvement in both grain yield and, to a lesser extent, groat percentage, resuited in an annual rate of increase in groat yield of 0.9%, slightly higher than that for grain yield. Kernel weight has increased over time, while the number of kernels per unit area has generally decreased. Newer cultivars thus reflect the emphasis that has often been placed on selection for yield and kernel quality and size. Biological yield, harvest index, total N (in groats plus straw), groat N, and N harvest index (NHI) were all greater newer cultivars, linearly related to cultivar age, and positively correlated with grain yield. Higher groat protein yield of modern cultivars was primarily a reflection of the gains in groat yield and improvement in NHI or N partitioning.
An apparatus was designed for simultaneous measurement of rates of N2 fixation estimated by C2H2-C2H4 assay (N21 C2H21 fixation) and N03-absorption by roots of intact, nodulated soybeans (Glycine max IL.I Merr.). The principal design features include: (a) a gas-tight mist chamber in which nodulated roots can be exposed simultaneously to C2H2 in the gas phase and to a lquid phase containing N03 sprayed in a fine mist; and (b) provision for sampling the gas phase for C2H4 determination, and the liquid phase for N03-determination.We studied N03-absorption by soybeans as affected by nodulation, N03-concentration during assay, and previous N nutrition during growth in nutrient solution culture in controlled environment chambers. It was established that 0.5 Mm N03-nearly saturated the N03-absorption system of both nodulated and unnodulated soybeans when the concentration dependence of NO3-absorption rate was measured just after flowering began. Nitrate absorption rates were measured after development of N stress in unnodulated plants, and during recovery from N stress in nodulated plants. The results suggested that the lower capacity for N03-absorption of nodulated plants was a consequence of N stress during the period of nodule growth and development.Nitrogen I C2H21 fixation rates were compared in intact plants assayed in the mist chamber and in excised roots assayed in both the mist chamber and in glass jars. Excised roots had a lower N21 C2H21 fixation rate than intact plants. The decline observed during the first hour after shoot removal was more pronounced for glass jar-assayed excised roots than for nist chamber-assayed excised roots.We discuss the advantages of our method for assessing the capability of a nodulated legume to acquire nitrogen through both N2 fixation and absorption and assimilation of N03-. A recent consequence has been a trend toward developing techniques and apparatus for in situ C2H2 reduction assays on intact nodulated legumes. Mederski and Streeter (11) devised a method for suspending soybean root systems in a gas-tight enclosure and spraying them with a nutrient mist. Acetylene reduction was then monitored over several days. Although that system was obviously well suited for ion absorption studies, no such investigation was reported. Zobel et al. (24) grew several legume species with well nodulated roots in an "aeroponic" system. Their success suggested that nodules both developed and functioned well in a nutrient mist. We were convinced that a mist or spray would serve equally well for short term studies of absorption kinetics for a single ion (NO3 ), and would also facilitate simultaneous measurements of the N2[C2H21-fixing activity of nodules.The objectives of the research reported here were to: (a) develop methodology that would facilitate simultaneous measurement on intact nodulated soybean plants of N03 absorption from a liquid phase, and reduction of C2H2 to C2H4 in a gas phase; (b) evaluate the method by comparison with previously developed techniques; and (c) determine w...
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