Screening for resistance against rhopalosiphum padi (L.). I. avena species and breeding lines

Summary Thirty-two accessions of Avena species and breeding lines were evaluated for resistance, primarily antibiosis, to the aphid Rhopalosiphum padi (L.) in greenhouse and growth room tests. The highest levels of resistance were found in A. barbata and in the perennial species A. macrostachya. One breeding line, Obee, was also found to have interesting resistance characters. Resistance in A. macrostachya is discussed in relation to perenniality. A different screening method for rapid testing of large collections of varieties is evaluated.     

Associations among productivity,production response,and stability indexes in oat varieties

Summary We tested three sets of oat varieties for grain yield in a series of environments and observed that generally more than 80% of the yield variation for individual varieties was due to linear regression response. Mean yields for varieties were significantly variable in all three sets, and regression response indexes were significantly variable in two of them.Mean yields over the three sets were correlated with regression response indexes with r=0.61. Associations of mean yield with the three stability parameters (i.e., coefficient of determination, mean square for deviations from regression, and ecovalence) were low and usually not significant. The correlation of regression response indexes with coefficients of determination was 0.42, but neither of the other stability parameters was associated with the response indexes. The three stability parameters were closely correlated with one another.Our materials were selected varieties, so evidently our results suggest what can be accomplished in breeding for combinations of mean production, production response, and productiom stability.Journal Paper No.J-9092 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, USA 50011. Project 1752. This work was supported in part by the International Atomic Energy Agency, vienna, Austria, in the form of a fellowship for the senior author.     

高寒区旱地莜麦合理种植密度的研究

通过对旱地莜麦不同种植密度的试验,进一步研究了密度对莜麦主要农艺状、干物质积累、叶面积系数及产量构成因素的影响,确定出在中等肥力条件下,晋北高寒区旱地莜麦的适宜种植密度为:播量600—675万粒/hm2,基本苗400—500万株/hm2。在该密度范围之内,群体和个体生长良好,产量各构成因素间关系协调,合理密植是获得旱地莜麦高产、稳产的关键技术。     

Selection for grain yield of oats via vegetative growth rates measured at anthesis and maturity

Summary Grain yield of oats can be improved by increasing either vegetative growth rate or harvest index, but these two traits are negatively associated. Currently, harvest index of oats is near an optimum at 45%, so further improvement in grain yield must come from increased vegetative growth rate. In this study, vegetative growth rate was measured at anthesis and at maturity by dividing vegetative dry weight at anthesis and straw yield, respectively, by days to heading. Genotypic correlations between the two estimates of vegetative growth rate ranged from 0.53 to 0.66. When the highest 10% of the lines were selected for the two growth rate measurements, the actual genetic gain in grain yield was 3.5% when vegetative growth at anthesis was used, and a slight decrease occurred when vegetative growth rate at maturity was used. Selection for either growth rate measurement caused associated increases in biological and straw yields and dry weight at anthesis.Journal Paper No. J-12129 of the Iowa and Home Econ. Exp. Stn., Ames, Iowa 50011. Project 2447. Part of a study conducted by the senior author while a visiting scientist at Iowa State University.     

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

Summary 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.     

Relationship between genealogical distance and breeding behaviour in oats (Avena sativa L.)

Summary Eight oat cultivars and experimental lines from four germplasm sources were crossed in a diallel mating design without reciprocals. F₁ heterosis for grain yield was evaluated in two experiments, and 48 F₂-derived lines from each of the 28 matings were evaluated for bundle weight, grain yield, straw yield, harvest index, height, and heading date in two experiments. Number of transgressive segregates per trait and generalized genetic variance were calculated for each mating. Genealogical distance for each mating was obtained by using coefficient of kinship based on the pedigree of the parents. The relationship between genealogical distance and the three types of breeding behaviour was examined via correlation and regression. Significant correlations occurred only for genealogical distance with numbers of transgressive segregates for height and with generalized genetic variances. Both were positive. Significant heterosis was observed for matings of more distantly related parents. Regressions on genealogical distance, when significant, were linear. Genealogical distance between parents was positive associated with diversity on the basis of breeding behavior.Journal Paper No. J-11874 of the Iowa Agriculture and Home Economics Station, Iowa State Univ., Ames, IA 50011. Project 2447.     

Disomic alien chromosome substitution and addition in hexaploid oat

Summary True-breeding, leaf rust (Puccinia coronata Cda. f. sp. avenae Fraser and Led.) resistant oat lines with somatic chromosome numbers of 42 and 44, were recovered in the advanced generations of a pentaploid hybrid from the cross between C.I. 7232, a leaf rust resistant and dark lemma colored derived tetraploid and Clarion, a susceptible hexaploid oat. Microsporocyte observations and breeding behaviour of these lines and their F₁ hybrids with susceptible hexaploid oat cultivars indicated that the 42- and 44-chromosome lines are disomic substitutions (20+1A) and disomic additions (21+1A), respectively, of the same alien chromosome which carries genes for dark colored lemma and leaf rust resistance. The substitution and addition lines possess good field resistance to leaf rust. Plants of substitution lines were less vigorous, shorter, with poor straw and reduced fertility. Addition lines had reduced tillering ability, plant vigour, culm thickness, leaf width and fertility and were late maturing. Progeny tests for resistance indicated that substitution lines are more stable than addition lines. It is suggested that these lines may be of value in a program of radiation-induced gene transfer.     

Repeatability of regression stability indexes for grain yield of oats (Avena sativa L.)

Summary Two lines of descent were established from an F₃ bulk lot of oats (Avena sativa L.) initiated by mixing seeds from approximately 250 crosses. For one line of descent, seeds were radiated with thermal neutrons or X-rays from F₃ through F₆, followed by five generations of bulk propagation. The second was propagated for 10 generations. No artificial selection was practiced in either line of descent. Grain yield data from 20 random strains from each of four generations from the radiated (F₇, F₈, F₉, and F₁₁) and five from the nonradiated (F₃, F₆, F₇, F₈, and F₁₂) line of descent and 20 check cultivars tested in 14 environments were used for estimating regression stability indexes of oat strains.The 14 environments were assigned randomly to two sets of seven, and regression stability indexes were computed for the 180 experimental oat strains for both sets. Intrageneration correlations between regression stability indexes from the two sets of environments ranged from –0.35 to 0.64 (18 d.f.), and only one of nine was significant, indicating poor repeatability for estimates of this statistic computed from different sets of environments.Correlations between regression stability indexes from two sets of environments, one in which the environments varied by soil nitrogen levels and a second in which they varied by soil phosphorus levels, ranged from –0.01 to 0.28, none of which was significant.The relative magnitudes and ranking of the regression stability index values for the oat genotypes were nearly identical when environmental productivity indexes were assessed with any number of check cultivars from 2 to 20.Journal paper No. J-8080 of the Iowa Agriculture and Home Economics Experiment Station. Ames. Iowa. USA 50010. Project 1752.     

施氮量和种植密度对石河子复播早熟饲用燕麦生产性能的影响

为探究施氮量和种植密度对复播早熟饲用燕麦（Avena sativa L.）产量和品质的影响,以‘青海444’（A1）,‘青引1号’（A2）,‘领袖’（A3）和‘青燕1号’（A4）为材料,采用两因素裂区设计,设施氮量为主区,分别为0.00 kg·hm^-2（B0）、80.00 kg·hm^-2（B1）、160.00 kg·hm^-2（B2）3个处理;设种植密度为副区,分别为168.00 kg·hm^-2（C1）、240.00 kg·hm^-2（C2）、312.00 kg·hm^-2（C3）3个处理。对各处理燕麦干草产量、株高、营养品质[干物质（Dry matter,DM）、粗蛋白（Crude protein,CP）、中性洗涤纤维（Neutral detergent fiber,NDF）、酸性洗涤纤维（Acid detergent fiber,ADF）和粗脂肪（Ether extract,EE）]分析,结果表明,施氮量和种植密度对燕麦DM,CP,ADF,NDF和EE含量有显著影响（P<0.05）,乳熟期随种植密度增加,DM,CP,NDF和ADF含量不断递减,随施氮量增加不断递增。综上,石河子地区4个饲用燕麦均适合在乳熟期收获,且‘青海444’为最佳种植品种,其最佳施氮量为80.00 kg·hm^-2,种植密度为312.00 kg·hm^-2。     

西藏高寒牧区燕麦作物系数的推求及验证

运用FAO-56推荐的单作物系数法和双作物系数法推求充分灌溉条件下西藏高寒牧区燕麦的作物系数,并通过灌溉试验数据验证所求作物系数的可靠性以及这2种方法在海拔4 000m以上地区的适用性。结果表明,基于单作物系数法,2011年和2012年作物系数Kcini、Kcmid、Kcend分别为1.06、1.18、0.28和1.09、1.17、0.28。2011年和2012年双作物系数法与单作物系数法计算的ETc拟合相关系数分别为0.743和0.894。理论计算的作物需水量与实测值接近,该2种作物系数法均适用于西藏高寒牧区。