Oat Lines Research Articles

Germination response to phytochrome depends on specific dormancy states in wild oat (Avena fatua)

Effects of brief red and far-red light on germination of seeds from dormant lines of wild oat (Avena fatua L.) were studied in combination with mechanical injury to the seed coat, application of gibberellin A3, or changes in relative humidity during afterripening. Aberrant germination responses to phytochrome action were observed in the mechanically injured seeds in some of the lines, i.e., brief red light inhibited or delayed germination induced by injury, and immediately following far-red light cancelled the negative effects. Phytochrome action influenced germination of the gibberellin-treated seeds in a normal fashion, although effects of the gibberellic acid and brief red light on germination were not additive. Brief red light inhibited germination of seeds afterripened in zero relative humidity; the same light promoted germination of those in 30 and 60% relative humidity. Germination response to phytochrome in wild oat depends on specific seed dormancy states, illustrated by genetic origins, dormancy-breaking methods and afterripening conditions. Key words: Avena fatua, dormancy, mechanical injury, gibberellin A3, phytochrome, relative humidity.

Selection for Yield and Stability among Oat Lines

Methods to simultaneously select for yield and stability need to be compared to determine which index is the best choice to identify high‐yielding, stable genotypes. A comparison of the repeatability of different measures of stability would be useful because stability statistics with high repeatability should be superior to identify stable genotypes. Stability measures were evaluated for 116 oat (Avena sativa L.) lines in 36 Iowa environments. The objectives were (i) to evaluate the mean selection differential when selection was for yield, stability statistics, or simultaneous selection for both yield and stability, using different indices; (ii) to compare repeatability of the stability regression (b1) stability variance component (σ21), and deviation from regression mean square (sd21) across random subsets of 18 environments; and (iii) estimate rank correlations between stability statistics and mean grain yield, in all environments. Simultaneous selection for yield and stability, based on three indices, identified high‐yielding, stable genotypes. Selection solely for yield identified genotypes with high mean yield that on average were not stable. Selection solely for each stability measure identified genotypes with low yield that were stable. The repeatability of b1 was 0.61, and the index that used this measure of stability combined with selection for yield identified 12 genotypes that yielded 3% less than the average of the highest yielding 12 genotypes. Repeatability of σ21 was 0.28 and repeatability of σ21 was 0.17. The correlation between yield and b1 was 0.73, between yield and σ21 was 0.21, and between yield and σ21 was 0.28.

Identification of a RAPD marker linked to the oat stem rust gene Pg3

The feasibility of identifying molecular markers linked to disease resistance genes in oats was investigated utilizing random primers in conjunction with polymerase chain reaction technology. A pair of near-isogenic oat lines were screened for polymorphic DNA fragments linked to the stem rust resistance gene Pg3. Two primers were identified which amplified DNA fragments that were polymorphic between the lines analyzed. One primer (ACOpR-2) was shown to be completely linked to the Pg3 locus; the other primer was not linked to either the ACOpR-2 or the Pg3 loci. This type of analysis, combined with rapid leaf disc DNA extraction techniques, offers an effective means of identifying useful molecular markers and of applying them to plant breeding selection strategies.

Resistance to Oat Crown Rust in Diploid and HexaploidAvena

The minimum number of Pc genes for resistance to oat crown rust (Puccinia coronata var. avenae) was determined from infection-type data based on the interactions of several oat lines and 47 isolates of crown rust from the Iowa State University collection. Infection-type data from seedlings of seven diploid oat accessions, a hexaploid chromosome addition line (X117), and its recurrent parent (C649), were evaluated in reference to 33 differentials to determine low or high infection type. At least 17 unique crown rust resistance genes can be detected in the hexaploid differentials with the Iowa State University crown rust collection. Four additional resistance genes can be detected among the diploid accessions (.)

Inheritance of Resistance to Loose Smut of Oat

The percentage of plants infected with loose smut (Ustilago avenae) was determined in oat (Avena sativa) parental cultivars and lines and in progenies after kernels were inoculated with water suspensions of teliospores by a vacuum procedure. Inheritance of resistance was studied with F 4 populations of three crosses. In cross Ogle/ND 820559 (susceptible/moderately resistant), the distribution of F 4 progenies appeared bimodal, with more of the progeny clustered around ND 820559 than around Ogle. Twenty-one percent of the F 4 lines displayed fewer infected plants than the resistant parent. In Don/Starter (resistantJresistant), the distribution of F 4 lines was skewed toward low incidence of infection, with many lines more susceptible than either parent

The oat line Pc54 as a source of resistance to crown rust, stem rust and powdery mildew in Europe

The oat line Pc54 was found to be resistant to powdery mildew under both field and glasshouse conditions. The ratio of resistant to susceptible F2 and F2 progeny of a cross between a selection from the Pc54 line (Cc7422) and a susceptible cultivar (Selma) showed that, in addition to carrying the crown rust resistance gene Pc54 and the pg15 gene for stem rust resistance, the mildew resistance of the Pc54 line was conditioned by a single incompletely dominant gene along with additional factors which modified the expression of resistance. Previous results, that there was no linkage between genes Pc54 and Pg15, were confirmed. In addition, there was no evidence of linkage between the mildew resistance gene and gene Pc54. Evaluation of selections from within the Pc54 line showed that the expression of both stem rust and mildew resistance was modified by, or linked to, plant height. The effectiveness of genes Pc54 and Pg15, as measured by virulence frequencies, in central and eastern Europe is described.

After-ripening and phytochrome action in seeds of dormant lines of wild oat (Avena fatua)

The effects of a short exposure to red, far-red or alternate red/far-red light on the germination of seeds after-ripened for different periods of time were studied in dormant lines of wild oat (Avena fatua L.). Three stages were distinguishable in the after-ripening period in the response of germination to light. Seeds stayed dormant and showed no response to light during stage I. Phytochrome-mediated germination was observed in seeds during stage II. The phytochrome action disappeared during stage III, i.e. seeds fully germinated following treatments of all light qualities. When the seeds were imbibed in polyethylene glycol solutions, dark germination was reduced and phytochrome again had an effect, which suggested the involvement of phytochrome in water uptake of the seed.

Field and greenhouse screening of oat seedlings for iron‐nutrition efficiency

Abstract Susceptible oat (Avena sativa L.) genotypes may express iron deficiency chlorosis when grown on calcareous soils. Known resistant ('Coker 227') and susceptible (TAM O‐312') cultivars were compared to 28 cultivars and breeding lines of oat in greenhouse and field plots. The soil used for both field and greenhouse studies was a Parrita sandy clay loam (Petrocalcic Paleustoll) with pH near 8.0. Previous research indicated that chlorosis expression was enhanced when seedlings were grown in saturated soils. Field plots were irrigated three times per week, while greenhouse seedlings were maintained in saturated soils after the 1.5 to 2‐leaf stage. Visual chlorosis scores were recorded in both field and greenhouse experiments. Individual seedlings were recovered from Super Cell Cone‐tainers when seedling were 3 to 4 week old, and data recorded on shoot and root length and dry weights. A root fibrousness score was also assigned. Root fibrousness was not highly related to chlorosis score (r = 0.25). Chlor...

Agronomic and Bioenergetic Consequences of Selection for High Groat‐Oil Content and High Protein Yield in Oat*

AbstractFew studies have examined the effects of selection for high oil or protein content on the chemical composition of cereal seeds. This study was conducted to examine agronomic and bioenergetic consequences that result with changes in the chemical composition of groats of oat (Avena sativa L.). Oat lines with low and high groat‐oil content (GO) and with low and high groat‐protein content (GP) were chosen from each of five cycles of a recurrent selection program for increasing GO and from each of four cycles of a recurrent selection program for increasing protein yield via elevating GP, respectively. These lines were evaluated at three Iowa locations in 1988. The results indicated that GP was not significantly affected by selection for high GO and that GO significantly increased during selection for high protein yield via elevating GP. Both selection procedures resulted in oat lines with higher groat‐energy contents. A bioenergetic cost analysis showed that for GO in the oil population and GP in the protein population to be increased, additional photosynthate needed to be available.

Correlated Response to Selection for Protein Yield in Oats After Three Cycles of Recurrent Selection

AbstractThree oat (Avena saliva L.) populations (i.e., lines of descent), high grain yield (HG), high protein content (HP), and high protein yield per se (HGP), each developed by three cycles of S, recurrent selection, were evaluated for the effect of selection for groat‐protein yield upon other agronomic traits. Selections making up the HG line of descent had high protein yield primarily due to high grain yield, and those selected for HP had high protein yield due to both high protein content and high grain yield. Selection in HGP was on the basis of protein yield per se. Selection caused increases in bundle weight, harvest index, vegetative growth rate, and seed number in all lines of descent. Heading date, plant height, and seed weight were unaffected, whereas groat percentage and test weight were decreased in HP and HGP. Heritabilities were high for heading date, plant height, test weight, and seed weight, moderate for harvest index and bundle weight, and low for groat percentage. Genetic variability generally declined from CO to C3 for all traits.Groat‐protein yield and amount of protein per groat increased in all lines of descent. In HG, the increase in groat weight was due primarily to increases in the nonprotein fraction, with groat‐protein content actually decreasing. In HGP, groat weight increased due to increases in protein and nonprotein fractions, and groat protein content remained constant. In HP, groat weight and amount of nonprotein per groat decreased, thus increasing groat‐protein content.Three cycles of recurrent selection resulted in oat lines with groat‐protein yields significantly higher than the highest lines from CO. Utilization of index selection may be desirable to obtain populations of greater breeding value.

Avenin Banding Pattern Variation in Tissue Culture‐Derived Oat Lines

Plant tissue culture generates genetic variation in crop plants. Biochemical variation from culture has not been examined in oat (Avena sativa L.) regenerants. The objectives of this study were to examine avenin (prolamine) variation in R5 generation oat lines derived from R1 progeny of tissue‐culture regenerated plants (R0) that had no detectable karyotypic aberrations, and to test for associations between avenin and agronomic trait variation. Avenins extracted from seed of 56 R4 ‘Lodi’ lines and 147 R4 ‘Tippecanoe’ lines were separated on horizontal isoelectric focusingels (pH 5‐8). The Lodi lines had no variant patterns. Three variant Tippecanoe patterns were observed. One (V1) was identified as the probable product an outcross and two as culture‐generated variant patterns. Variant V2 was found in one line and had a new band at pI 7.85. The third variant (V3) was found in 23 of the 147 Tippecanoe lines and occurred in regenerants from three independent embryo‐derived cultures. Two‐dimensional gel electrophoresis indicated that one of the band differences in these variants came from production of a new 27‐kDa protein. The 23 lines with the V3 avenin variant pattern were further characterized by agronomic trait comparisons. These V3 lines were shorter and later than controls, had increased seed weight, seed number, grain yield, and bundle weight, and they had decreased seed protein and flag leaf area. These results indicate that biochemical variation is generated in oat tissue cultures and that some variant types occur at high frequencies. Avenin banding pattern evaluation should be useful in identifying the products of outcrosses and may provide molecular markers for agronomic traits.

Combining Ability for Test Weight and Agronomic Traits of Oat

The relative importance of additive and nonadditive variation for agronomic traits provides guidelines for setting breeding strategies for cultivar development. To estimate the relative importance of general and specific combining ability (GCA and SCA) for five traits of oat (Avena sativa L.), 24 oat genotypes were mated according to a Design II scheme. The 24 parents were a sample from elite germplasm available for cultivar development at Iowa State University and in various regions of the USA. Test weight, grain yield, harvest index, date of heading, and plant height were measured for 10 random F2‐derived F3 lines from each of 95 crosses. The oat lines were evaluated in 1988 in four replicates at each of three locations in Iowa. Both GCA and SCA were significant (P ≤ 0.01) for all traits; GCA, however, accounted for 75% of the variability among crosses for test weight, 85% for grain yield, 82% for harvest index, 72% for date of heading, and 85% for plant height. We speculate that additive ✕ additive epistasis was primarily responsible for the observed significant SCA because the estimate of SCA represents 1/4 σ2D + 1/2 σ2AA, and in our experiment σ2D seemed small (based on contrasts of parent vs. offspring means). We suggest that breeders use mild selection intensities in early generations of inbreeding to avoid discarding lines before favorable epistatic combinations form. In regard to parent selection, our results indicate that most parents could be used as male or female in a cross without affecting segregation for these five traits; however, midparent values alone do not adequately predict which crosses produce the most outstanding lines.

A New Greenbug Virulent to E‐Biotype Resistant Sorghum

Sorghum [Sorghum bicolor (L.) Moench] hybrids resistant to Biotype E greenbug [Schizaphis graminum (Rondani)] had more damage than expected when heavily infested with greenbugs daring August, 1990. Greenbugs isolated from severely damaged plants of resistant sorghum in Stevens County, Kansas, were tested for virulence to Biotype‐E resistant cultivars and lines of sorghum, wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), oat (Arena sativa L.), and rye (Secale cereale L.). Greenhouse tests involving seedling plants indicated that the sorghum fines with resistance to Biotype E were susceptible to the greenbug isolate from Stevens County. The only sorghum germplasm fine that appeared resistant to this isolate was PI 266965. Small grains with resistance to Biotype‐E greenbug retained their resistance to the new isolate. Because no previously designated biotypes have shown virulence to Biotype‐E resistant sorghum, the greenbug isolate from Stevens County was designated Biotype I. If Biotype I replaces Biotype E in the field, in a similar fashion to the replacement of Biotype C by Biotype E during the 1980s, greenbug resistance now available in sorghum will be compromised and sorghum production will be vulnerable to the new biotype.

Changes in fatty acid composition associated with recurrent selection for groat-oil content in oat

Groat oil of oat (Avena sativa L.) is a well-balanced oil with respect to saturated, monounsaturated, and polyunsaturated fatty acids. In this study, we measured the effect of six cycles of recurrent selection for high groat-oil content on the fatty acid composition of the groat oil. From each cycle of selection, 50 oat lines were grown in a replicated field experiment at two sites and were evaluated for groat-oil content and fatty acid composition.

Extraction and identification of antioxidants in oats

Eight separate solvent systems were used with groats and hulls of several lines of oats to determine which system resulted in the most effective, rapid extraction of antioxidants. Antioxidant activity at room temperature was estimated by using thin‐layer chromatography (TLC) along with a β‐carotene spray. The greatest antioxidant activities were obtained with methanolic antioxidant extracts derived from Noble and Ogle oats and hulls. These extracts were added to soybean oil (SBO) and their effectiveness was compared with that of butylated hydroxytoluene (BHT), tertiary butyl hydroquinone (TBHQ) and a control (no additives) at 32°C, 60°C and 180°C. A petroleum ether extract of Noble oats also was tested in SBO at 180°C. Peroxide values (PV) for oils with added antioxidants during storage at 32°C and 60°C showed that the Ogle oat extract was more effective than the other oat and hull extracts or the control. There were no significant differences in effectiveness among the extracts and the control at 60°C. At 180°C, the stability of each oil was determined by measuring conjugated dienoic acid values (CD) and the relative amounts of the unoxidized fatty acid methyl esters (FAME) 18:2, 18:3 and 18:2/16:0. All oils with added oat and hull extracts had significantly lower CD and significantly higher 18:2/16:0 than oils with added BHT, TBHQ or the control during 14 days at frying temperature. Phenolic and hydroxy‐phenolic antioxidant compounds with acids, alcohols, sugars or glycerides attached were tentatively identified in the oat and hull extracts by using TLC and Chromatographic sprays.

Selection for Groat‐Oil Content in Oat Grown in Field and Greenhouse

Selection for quantitative traits of oat (Avena sativa L.) usually is based on field experiments. The objective of this study was to determine whether a greenhouse could be utilized to select for greater groat‐oil content in oat. Forty‐eight oat lines from the C0 to C3 of a recurrent selection program to increase groat‐oil content were evaluated in the field and greenhouse in 1987 and 1988. Groat‐oil contents of large and small samples of oat groats were determined for each entry in each environment except for small samples from the greenhouse in 1987. The genetic correlation between groat‐oil contents of field‐ and greenhouse‐grown plants was 0.87, and between groat‐oil contents of large and small samples 1.14. Estimates of heritabilities, variances, and genetic correlations were used to compute the predicted genetic gains, expressed under field conditions, from one cycle of each of three recurrent selection regimes. A regime that utilized selection among S0 plants in the field followed by selection among and within selected S0:1 progenies in the greenhouse gave annual predicted gains in groat‐oil content that were 38 and 186% greater than predicted gains from phenotypic recurrent selection regimes with selection among field‐ and greenhouse‐grown S0 plants, respectively. Thus, selection for groat‐oil content in oat on the basis of data from the greenhouse can be successfully incorporated into a recurrent selection program.

Growth analyses of oat lines with low and high groat-oil content

A considerable increase in groat-oil content of oat (Avena sativa L.) has been accomplished recently. The objective of this study was to determine whether physiological traits of oat plants with high groat-oil content are changed in a way that would provide the energy needed for increased groat-oil content. Growth analyses were conducted in 1987 and 1988 on 25 oat lines with low and on 25 with high groat-oil content. Three harvests were made in 1987 and six in 1988. Plot biomass, plant weight, leaf area, and leaf weight were measured at each harvest and estimates for relative crop growth rate, unit leaf area, leaf area ratio, specific leaf area, and leaf weight ratio were derived. Grain yield, groat-oil content, and groat-protein content were measured at maturity. The data were analysed by using the stepwise multivariate analysis of variance technique. The results suggest that changes in growth characteristics and increases in photosynthetic capacity provide the extra bioenergy required for synthesis of more groat oil. The groat-protein content did not change as a result of increased groat-oil content in oat.

The evaluation of adult plant resistance to powdery mildew (Erysiphe graminis f.sp. avenae) in transgressive lines of oats

Previously identified segregant lines of oats with levels of adult plant resistance to powdery mildew (Erysiphe graminis f.sp. avenae) better than the resistant parent maintained this high level of resistance in field nurseries over two growing seasons. This enhancement was not expressed on inoculated detached leaves under laboratory conditions where no differences between the more resistant parent cv. Maldwyn and the most resistant segregants was detected. Reduced resistance was not detected in tests where leaf segments of the transgressive lines were inoculated with ‘trained’ isolates. Problems associated with selecting for adult plant resistance under both field and laboratory conditions are discussed.

Reaction of Winter Oat Germ Plasm to an Epidemic of Oat Powdery Mildew

In the spring of 1989, an epidemic of oat powdery mildew occurred naturally in four randomized blocks near Tifton, Georgia, in which 31 winter oat lines had been planted in the fall of 1988, Plots were rated on 14 and 18 April for percentage of foliage covered with mildew and for infection type (0-4 scale). Differences existed among cultivars on both assessment dates. Severity levels increased from a mean of 29.2 to 32.9% between assessment dates, and all cultivars showed symptoms; oat lines ranged from 7.5 to 59,4% in severity and from 1.4 to 4.0 in infection type (...)

Agronomic Trait Variation in Oat Lines Derived from Tissue Culture

Tissue culture may generate agronomic variation that is potentially useful in plant improvement. This somaclonal variation, if extensive, could pose problems when tissue culture is a component of genetic transformation or when in vitro selection procedures are used. The objective of this study was to analyze agronomic trait variation in R4 and R5 generation oat (Avena sativa L.) lines derived from R1 progeny of tissue‐culture regenerated plants (R0) that had been previously classified as having no karyotypic aberrations. Fifty‐six R4 and R5 ‘Lodi’ lines tracing to 11 R0 plants, and 213 R4 and 147 selected R5 ‘Tippecanoe’ lines tracing to 45 R0 plants were evaluated. Lines were planted in hill plots in radomized complete‐block designs with six replicates and evaluated for 2 yr at two locations. Traits analyzed were height, heading date, seed protein, flag leaf area, seed weight, seed number, grain yield, and bundle weight. Significant variation (P < 0.05) was detedted for all traits both within families (lines derived from the same R0 plant), and when lines and families were compared with the parental cultivars. Eighty‐two percent of the Lodi families and 93% of the Tippecanoe families had significant changes for at least one of the eight traits measured. Although agronomically less desirable changes were more frequent than desirable changes, liens with increases and lines with decreases were found for each trait. One cycle of successful bidirectional selection among culture‐derived lines demonstrated that the trait changes were heritable and that individual lines could be selected for use in plant improvement programs. The variation observed also demonstrates that materials produced by using directed genetic manipulation involving tissue culture should be tested extensively for possible quantitative trait variation.