Oat (Avena sativa L.) genotypes differ in their patterns of growth and development in response to vernalization (cold temperatures applied to germinating seeds). Genomic regions controlling vernalization response in heading date, plant height, and tiller number were mapped in a recombinant inbred (RI) population derived from the cross of oat cultivars ‘Kanota’ (vernalization‐responsive) and ‘Ogle’ (vernalization‐insensitive).Seventy‐one F6‐derived RI lines were subjected to vernalization and no‐vernalization treatments, and then grown in growth chambers. A genetic linkage map of 561 (primarily RFLP) loci was used to identify quantitativet rait loci (QTLs) affecting the traits in vernalized and non‐vernalized plants. Nine to 16 linkage groups and unlinked loci were associated with each trait assessed herein. Individual loci explained up to 37% of the phenotypic variation. Three to five significant loci were included in multiple locus linear models which explained up to 66% of phenotypic variation for each trait. One to 14 interactions between loci were found for each trait. The interactions explained up to 30% of the phenotypic variation not accounted for by the main effects of loci involved in the interactions. Inclusion of epistatic interactions tended to improve the fit of multiple locus models. As much as 83% of phenotypic variation was explained by multiple locus models including epistasis. Numerous epistatic interactions involving at least one locus with no significant main effect were detected.

The practice of sprouting is widely used to improve the nutritional value of grain seeds. Several nutritive factors such as vitamin concentrations and bioavailability of trace elements and minerals increase during germination. The objective of this work was to study the enrichment of various essential trace elements during germination of wheat (Triticum aestivum), buckwheat (Fagopyrum esculentum), and quinoa (Chenopodium quinoa) seeds in order to improve their nutritional role as a source of bioavailable trace elements. Seeds were sprouted either in distilled- or tap-water and in five different electrolyte solutions to investigate the concentration-dependent uptake. The time-dependence was investigated by analyzing aliquots of the sprouts after certain germination periods. Samples were analyzed after freeze drying for their Li, V, Cr, Fe, Mn, Co, Cu, Zn, Sr, Mo, As and Se concentrations with inductively-coupled plasma mass-spectrometry (ICP-MS). As a control for possible changes in the biochemical metabolism of the sprouts, the biosynthesis of vitamin C was also determined by using reversed-phase ion-pair HPLC. It was shown that quinoa was the most resistant to the applied electrolyte solutions and had the highest uptake rates for almost all elements, followed by buckwheat and wheat. Greatest increases were observed for Co, Sr, and Li. No significant changes in vitamin C biosynthesis were observed between sprouts grown in different electrolyte solutions. The time-dependent uptake for most elements was characterized by a significant absorption during soaking of the seeds, followed by a lag phase during the first day of germination and an increased uptake during the second and third day. Se and As showed distinctly different uptake behaviors.

Patterns of restriction fragment length polymorphisms (RFLPs) have been proposed as estimators of genetic diversity among breeding lines and as predictors of heterosis and genetic variance. We evaluated these proposals by using a set of nine elite oat lines crossed in a diallel mating design without reciprocals. RFLP analysis was conducted using HindIII-digested DNA and a total of 107 probes from three different sources: 14 heterologous wheat cDNA clones, 17 oat genomic clones, and 76 oat cDNA clones. Of the 77 probes that produced high-quality autoradiographs, 26 detected polymorphisms among this set of lines, with an average of 2.6 variants per probe. RFLP-based genetic distance (FD) was calculated from these data by using Nei and Li's measure of genetic similarity, and was compared with two other measures of genetic divergence. Genealogical distance (GD (*)) was obtained from the coefficients of parentage based on known parental pedigrees, and multivariate distance (DI) was calculated by using the first five principal components of the parental correlation matrix for 12 agronomic traits. FD was significantly correlated with GD (*) (r=0.63, P<0.01), but not with DI (r=-0.05). Cluster analysis based on these three distance estimates did not produce equivalent groupings, but the FD and GD (*) clusters were more similar to each other than to the DI clusters. These results indicate that: (1) sufficient variation exists for further application of RFLP technologyto oats, (2) RFLPs could provide accurate estimates of genetic divergence among elite oat lines, and (3) it is unlikely that dispersed markers can predict heterosis or population genetic variance in oats. Further investigations will require more parental lines, a larger set of markers, and more information on the linkage relationships between RFLP markers and loci controlling the trait of interest.

No abstract

Analysis of yield into components may provide information for devising efficient selection strategies for improving yield or traits correlated with yield in cereal crops. Our objective was to analyze changes in yield components associated with increased groat yields observed within three S1‐recurrent selection programs for high protein yield (grain yield × groat‐protein concentration) in oat (Avena sativa L.). Selection emphasized high protein yield per se (HGP), with no restrictions in grain yield or groat‐protein concentration; high protein yield due only to high grain (HG) yield; and high protein yield due to both high groat‐protein concentration and high grain yield (HP). Responses of yield components to these selection criteria were evaluated by growing 30 to 60 random S0‐derived lines from each selection cycle (C) in a hill plot experiment at two Iowa locations in 1989. Above ground biomass increased 7%, vegetative growth index (vegetative yield/number of days to heading) increased 9%, and groat index (groat yield/biomass) increased 8% from C0 to C5 in HGP. Changes in biomass, vegetative growth index, and groat index from C0 to C5 of HG were similar to those of HGP in direction, but were greater in magnitude (15,13, and 17% increases, respectively). Biomass increased by 5% from C0 to C5 in HP, but vegetative growth index and groat index did not change significantly. Seed number per plot increased in HGP by 16.6%, in HG by 28.2%, and in HP by 11.4%. Groat weight remained unchanged in all three lines of descent. Thus, the increased groat yields in all lines of descent were due first to greater biomass and second to high seed numbers.

In vitro toxin sensitivity has been correlated with in vivo disease resistance for several crop species but little has been reported on the association between disease resistance of the sporophyte and pathotoxin sensitivity in the gametophyte. The objectives of this research were to study the response of the gametophytic and sporophytic generations to cercosporin (CN) and cercospora beticola toxin (CBT) and to determine toxin sensitivity of sugarbeet (Beta vulgaris L.) lines with known levels of leaf spot resistance. Three sugarbeet lines having variedegrees of field resistance to Cercospora leaf spot were evaluated for sensitivity to two pathotoxins produced by the causal fungus, Cercospora beticola Sacc. The toxins, CN and CBT, were isolated and purified from cultures of the fungus, then applied singly or in varied combinations to leaf disks (sporophytic generation) or pollen (gametophytic generation). The CN CBT, separately or together, caused cellular leakage of Na and K in the sporophytic generation and potassium only in the gametophytic generation. This effect was toxin‐concentration dependent, but without synergism. In the sporophytic generation, the least ion leakage response to either toxin occurred in leaf disks taken from the most disease resistant of the three lines evaluated. Gametophyticion leakage responses to the toxins also were significant, but these responses were not directly correlated with leaf disk ion leakage or with sporophytic field disease resistance. The techniques facilitated a controlled study of CN and CBT sensitivity in the sporophytic and gametophytic generations of sugarbeet.

No abstract

Field trials were conducted to assess the benefit of combining a transgenic soybean cyst nematode (SCN) resistance trait, Cry14Ab-1 expressed by the event GMB151, with the native resistance allele rhg1b from PI 88788. The GMB151 event and rhg1b were crossed into common genetic backgrounds and segregated out to create four genetically related lines within each background. The lines created contained both native and transgenic resistance (rhg1b + GMB151), only native resistance (rhg1b alone), only transgenic resistance (GMB151 alone), or neither resistance type (susceptible). The benefit of GMB151 and rhg1b for SCN management was evaluated by measuring SCN control and yield protection. Soybean cyst nematode control was assessed by counting the number of females and cysts on roots early in the season and measuring the change in SCN egg population density over the entire season. The GMB151 transgenic event and the native resistance allele rhg1b both reduced early season SCN reproduction and contributed to significantly higher soybean yield. Compared to susceptible lines, the rhg1b allele improved yield by 33%, while GMB151 improved yield by 13%. Combining the GMB151 event and rhg1b allele resulted in greater SCN control and yield improvement than either provided alone. The combination of GMB151 and rhg1b reduced season-long SCN reproduction by 50% and resulted in 44% greater yield than the susceptible lines. Soybean cyst nematode virulence to rhg1b continues to increase due to the continuous planting of PI 88788-derived resistant cultivars. Pyramiding GMB151 with rhg1b provides a new management option to improve SCN control and soybean yield.