Mass selection for seed width in oat populations

Heterogeneous and segregating oat populations subjected to no selection and to mass selection for seed width for five consecutive generations were evaluated for 100-seed weight, heading date and plant height.The mass-selection technique, which consisted of passing the seeds over a screen with 12.7×2.4 mm slots and propagating the seeds too wide to go through the slots, was repeated for five consecutive generations (F₃ through F₇). Comparable unselected populations were grown each year. Remnant seeds from each check and mass-selected population were stored for future studies.In 1963, 500 random seeds from each of the six unselected populations (F₂ through F₇), from each of the five mass-selected populations (F₃ through F₇) and from a pure line were space-planted in the field. In 1964, the progenies from 75 random strains (a strain was the progeny of one spaced plant) from each of the 12 populations were sown in a randomized-block experiment with three replicates. In 1966, the strains from the last (F₇) generation of the unselected and mass-selected lines of descent (75 strains from each) were tested for yield in a 7-replicate randomized block experiment.The mass-selection technique increased the mean 100-seed weight, whereas in the unselected line of descent, the mean 100-seed weight did not change. The mean heading dates became later and the mean plant heights taller with the mass-selection procedure. The mean yield of the final mass-selection population was nine percent higher than that of the comparable unselected population.In spite of the associated changes between 100-seed weight and plant height and heading date in successive generations; the genotypic correlations among strains within populations indicated that these three traits were inherited independently. In advanced generations (F₆ and F₇), the genotypic variances for heading date and 100-seed weight were reduced in both the unselected and mass-selected lines of descent, whereas, for plant height no significant change occurred in either.Journal No. J-5586 of the Iowa Agricultural and Home Economics Experiment Station, Ames, Iowa, Project 1176. In cooperation with the Crops Research Division, Agricultural Research Service. U.S. Department of Agriculture.Professor of Plant Breeding.     

Recurrent selection in oat for adaptation to diverse environments

In order to test if selection can improve a population's adaptation to diverse environments simultaneously, three cycles of recurrent selection based on grain yield in Iowa, Idaho, and Norway were practiced in an oat (Avena sativaL.) population developed from North American, Scandinavian, and wild species (A. sterilis L.) germplasm sources. Specific objectives were to determine if selection: increased mean yields across environments and within all environments; changed the genetic correlation of yields in different environments; and changed genetic variation for yield within the population. We evaluated 100 to 210 randomly-chosen families from each cycle of selection at three Iowa locations, in Idaho, and in Norway for two years. Grain yield within each location and mean yields across locations increased significantly over cycles of selection. Mean yields across locations expressed as a percent of the original population mean increased at a rate of 2.6% per year. Several families from the third cycle population exhibited both high mean yields across locations and consistently high yields within all locations. Average genetic correlations of yield in different environments were higher in the second cycle than in the original population. A trend of reduced genetic variation and heritability was observed in Iowa only. These results suggest that we successfully improved mean population yield both within and across locations, and yield stability across environments, and in developing families with outstanding adaptation to diverse environments. This revised version was published online in July 2006 with corrections to the Cover Date.     

Productive oat ideotype for northern growing conditions

Summary Yield formation of four Finnish and three Nordic oat varieties and 12 breeding lines developed at the Hankkija Plant Breeding Institute was studied during four different growing seasons (1986–1989). Seventeen characteristics were measured, including traits representing the date of maturity and architecture of the oat stand. The variation between genotypes in the examined traits was studied by means of two-way analysis of variance. The relationship between grain yield and morpho-physiological traits was studied by means of simple correlation analysis and stepwise regression analysis.The present study, carried out in highly dissimilar growing seasons, showed that ideotype breeding in the northern growing areas is likely to be successful only in moderate to optimal growing conditions. Based on the findings of this study, a productive oat ideotype for northern cultivation is composed of traits such as early maturation, high phytomass production with a high panicle weight resulting from a large number of grains. short straw length (high resistance to lodging), and reduced tillering. The importance of other factors influencing oat breeding in northern growing conditions is discussed.     

Evaluation of cassava germplasm for drought tolerance under field conditions

The development of cassava (Manihot esculenta Crantz) with a high yield under water-deficit conditions is one of the goal of the breeding programs. The objective of this study was to evaluate the performance and to select cassava accessions based on drought tolerance indices and productive potential under water stress. Forty-nine accessions were evaluated for five agronomic traits (plant height—PH, root yield—RoY, shoot yield—ShY, harvest index—HI; and dry matter content of roots—DMC) under full irrigation conditions and drought stress (DS). The accessions were selected based on: (i) high yield under drought conditions (HY-DS) and (ii) high drought tolerance (Dr-To) based on six different indices. Overall, water stress dramatically reduced the traits’ means (RoY—72.98%, ShY—54.95%, DMC—26.15%, HI—31.05%, and PH—32.95%). Low coincidence among the top ten accessions was identified based on HY-DS and Dr-To criteria. Therefore, considering only the most important traits (RoY and ShY), five accessions (BGM0815, BGM0598, 9624-09, BGM0818, and BRS Formosa) presented high HY-DS. In contrast, to Dr-To criterion, eight and nine accessions were selected for high yield of the aerial part (ShY and PH) and roots (RoY and DMC), respectively. The mean productivity, geometric mean productivity, and drought tolerance indices were the most promising to identify genotypes with high agronomic attributes, while drought susceptibility index, susceptibility, and yield stability index were suitable to identify the most drought tolerant accessions. This set of selected accessions can be used in breeding programs aimed at high yield and drought tolerance.     

Mapping QTLs for aluminum tolerance in maize

Aluminum toxicity is one of the major constraints for plant development in acid soils, limiting food production in many countries. Cultivars genetically adapted to acid soils may offer an environmental compatible solution, providing a sustainable agriculture system. The aim of this work was to identify genomic regions associated with Al tolerance in maize, and to quantify the genetic effects on the phenotypic variation. A population of 168F_3:4 families derived from a cross between two contrasting maize inbred lines for Al tolerance was evaluated using the NSRL and RSRL parameters in nutrient solution containing toxic level of aluminum. Variance analyses indicated that the NSRL was the most reliable phenotypicindex to measure Al tolerance in the population, being used for further QTL mapping analysis. RFLP and SSR markers were selected for bulked segregant analysis, and additional SSR markers, flanking the polymorphisms of interest, were chosen in order to saturate the putative target regions. Seven linkage groups were constructed using 17 RFLP and 34 SSR markers. Five QTLs were mapped on chromosomes 2, 6 and 8, explaining 60% of the phenotypic variation. QTL₄ and marker umc043 were located on chromosomes 8and 5, close to genes encoding for enzymes involved in the organic acids synthesis pathways, a widely proposed mechanism for Al tolerance in plants. QTL₂ was mapped in the same region as Alm2,also associated with Al tolerance in maize. In addition, dominant and additive effects were important in the control of this trait in maize. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cold stress tolerance of soybeans during flowering: QTL mapping and efficient selection strategies under controlled conditions

Breeding soybeans for higher latitudes requires cultivars with an increased chilling stress tolerance, especially when flowering occurs. Phenotyping in climate chambers to select for this trait is labour‐intensive and requires an optimal allocation of resources due to limited space. We screened a diversity panel of 35 early maturity cultivars and a biparental population of 103 RILs for their cold stress tolerance at flowering stage. Pod number under control and stress conditions is highly heritable and showed only a weak correlation between the two treatments. Based on different testing scenarios, we could show that testing more genotypes with less replicates yields much higher responses to selection and hence should be pursued in such climate‐controlled experiments. We identified quantitative trait loci (QTL) for pod number under both conditions (chromosomes 7 and 13) and a cold tolerance‐specific QTL (chromosome 11). Furthermore, we performed genomic predictions using different test set scenarios and prediction models, showing that genomic prediction is a promising tool to select for cold stress tolerance, particularly if known QTL can be used as fixed effects in the model.     

Evaluation of Al-tolerance on upland and lowland types of NERICA lines under hydroponic conditions

We evaluated Al-tolerance in 44 interspecific lines (32 upland and 12 lowland) developed from the crosses of Oryza sativa and O. glaberrima called New Rice for Africa (NERICA) with 2 O. glaberrima lines and 13 O. sativa varieties under hydroponic culture containing 0.15, 0.3, 0.6, and 1.2 mM Al (+Al) and 0 mM Al (?Al as a control). Ten upland and four lowland NERICA lines showed strong Al-tolerance judging from their higher relative root and shoot dry weights (percentage ratios of dry weights in the Al treatments to the control) than those of the tolerant O. sativa check of IR 53650. Their tolerance was supported by relatively higher root Al accumulation (dark blue color) opposite performance with common knowledge (shown pale blue color) in root using hematoxylin staining compared to the Al-susceptible genotypes identified based on relative root and shoot dry weights in the study. Net Al concentration was higher in roots than in shoots in all +Al conditions for all genotypes; however, a clear difference in the Al concentration among the Al-tolerant, Al-moderately tolerant, and Al-susceptible genotypes was observed in the shoots. Al concentrations in the shoots of the Al-tolerant and Al-moderately tolerant upland and lowland NERICA lines were significantly lower than those of its Al-susceptible counterparts in the groups under 0.6 and 1.2 mM Al conditions, respectively. Differences in root and shoot growth among the Al-tolerant, Al-moderately tolerant, and Al-susceptible NERICA lines were clearer under strong Al toxic conditions (0.6 and 1.2 mM Al) than under weak Al toxic conditions (0.15 and 0.3 mM Al).     

Relationship of Fe-tolerance to morphological changes in roots in upland NERICA lines under Fe-treated hydroponic conditions

Twenty-six upland lines of New Rice for Africa (NERICA) were tested with four Oryza sativa varieties in relation to Fe toxicity tolerance under hydroponic culture containing 1.44 mM Fe (+Fe) and 0 mM Fe (-Fe as a control). Three NERICAs, WAB450-IBP-24-HB (P24), WAB450-IBP-82-1-1 (P82), and WAB450-IBP-163-3-1 (P163) among the 30 lines/varieties tested possessed relatively strong tolerance judging from reduction of root length and dry weight and shoot dry weight in +Fe compared to -Fe and from iron toxicity score (ITS) in +Fe. Only P24, P82, and P163 showed emerged lateral roots from pericycle at the root elongation zone, whereas in the other 23 NERICAs and four O. sativa varieties lateral root was not observed in the root elongation or differentiation zones. Less disruption of cortex on root tissues was observed in P24, P82, and P163 than in WAB450-16-2-BL2-DV2 (BL2-DV2), the most susceptible NERICA identified. P24, P82, and P163 showed significantly lower Fe content in the shoots than BL2-DV2, suggesting that the tolerant NERICAs could have some mechanism to inhibit the absorption of Fe. The emergence of lateral roots from the root elongation zone in the three tolerant NERICAs would be closely associated with reducing Fe absorption into the plants.     

Recurrent selection for broad adaptation affects stability of oat

A recurrent selection program for adaptation to diverse environments was successful in improving mean oat (Avena sativa L.) grain yield within and across testing environments. The objectives of this research were to determine if this selection program also resulted in changes in other agronomic traits or altered yield stability. Additionally, we investigated how selection modified the response of genotypes to climatic conditions. We evaluated random samples of 100 families from the original population and each of three selection cycle populations in replicated yield trials in Idaho, Iowa, and Norway for two years. Yield stability was assessed via joint regression analysis and superiority analysis. For each cycle, genetic relationships among yields observed indifferent environments were assessed by estimating phenotypic correlations between pairs of target environments. The effect of climate variables on genotype-by-environment interaction (GEI) responses was determined with partial least squares regression. Selection resulted in a small increase in mean heading date, a decrease in mean test weight, and no change in total above-ground biomass or plant height. Genotypic regression coefficients on environmental indices and deviations from regression were larger in the last cycle population, but superiority analysis demonstrated that selection significantly improved the adaptability of the population to the target testing environments. Improved adaptation was also demonstrated by increased phenotypic correlations among the most divergent pairs of environments in the later cycles. Partial least squares regression of GEI effects on climate variables suggested that later cycle families tended to respond more favorably to cooler than average conditions than the original population. Selection resulted in improved yield stability as well as improved mean yield. This revised version was published online in August 2006 with corrections to the Cover Date.     

Capturing genetic variability and selection of traits for heat tolerance in a chickpea recombinant inbred line (RIL) population under field conditions

Chickpea is the most important pulse crop globally after dry beans. Climate change and increased cropping intensity are forcing chickpea cultivation to relatively higher temperature environments. To assess the genetic variability and identify heat responsive traits, a set of 296 F_8–9 recombinant inbred lines (RILs) of the cross ICC 4567 (heat sensitive) × ICC 15614 (heat tolerant) was evaluated under field conditions at ICRISAT, Patancheru, India. The experiment was conducted in an alpha lattice design with three replications during the summer seasons of 2013 and 2014 (heat stress environments, average temperature 35 °C and above), and post-rainy season of 2013 (non-stress environment, max. temperature below 30 °C). A two-fold variation for number of filled pods (FPod), total number of seeds (TS), harvest index (HI), percent pod setting (%PodSet) and grain yield (GY) was observed in the RILs under stress environments compared to non-stress environment. A yield penalty ranging from 22.26% (summer 2013) to 33.30% (summer 2014) was recorded in stress environments. Seed mass measured as 100-seed weight (HSW) was the least affected (6 and 7% reduction) trait, while %PodSet was the most affected (45.86 and 44.31% reduction) trait by high temperatures. Mixed model analysis of variance revealed a high genotypic coefficient of variation (GCV) (23.29–30.22%), phenotypic coefficient of variation (PCV) (25.69–32.44%) along with high heritability (80.89–86.89%) for FPod, TS, %PodSet and GY across the heat stress environments. Correlation studies (r = 0.61–0.97) and principal component analysis (PCA) revealed a strong positive association among the traits GY, FPod, VS and %PodSet under stress environments. Path analysis results showed that TS was the major direct and FPod was the major indirect contributors to GY under heat stress environments. Therefore, the traits that are good indicators of high grain yield under heat stress can be used in indirect selection for developing heat tolerant chickpea cultivars. Moreover, the presence of large genetic variation for heat tolerance in the population may provide an opportunity to use the RILs in future-heat tolerance breeding programme in chickpea.     

Evaluation of aluminium tolerance in a spring rye collection by hydroponic screening

Aluminium (A1) tolerance of 63 rye accessions from a world spring rye collection was evaluated using the haematoxylin method and the root growth method. The haematoxylin method is based on the ability of A1‐tolerant seedlings to continue root growth following a short pulse treatment with a high Al concentration, while the root growth method uses the root growth and root tolerance index to judge A1 tolerance. Significantly higher levels of A1 tolerance were found in rye than in the A1‐tolerant bread wheat cultivar ‘Maringa’. Under the assumption that the ability of roots to grow under A1 stress is a combination of root vigour (long roots) and A1 tolerance, a hypothesis allowing for the differentiation of five genotype classes was suggested. This study demonstrated that the haematoxylin method and the root growth parameter identify genotypes with long root growth under A1 stress, but failed to detect A1 tolerance in genotypes with poor root vigour. These genotypes can only be identified using the root tolerance index parameter. However, the haematoxylin method is highly suitable for screening large segregating populations derived from improved germplasm that has been preselected for agronomically preferable traits, including plant vigour.     

Combining ability for grain chemistry quality traits in a white oat diallelic cross

There has been a strong demand for oat genotypes that contain caryopsis with high chemical quality which can suit the different market niches. Therefore, the objectives of this study were to assess the general (GCA) and specific combining ability (SCA) of white oat cultivars through diallelic crosses providing information about the genetic effects on expression of grain chemical quality components. Also, it was aimed to estimate the heterosis on F₁ and F₂ generations and the vigor loss due to inbreeding. During 2008, 21 hybrid populations F₁ and F₂ were obtained from artificial crossing among seven Brazilian white oat cultivars, following the complete diallel design, without considering the reciprocals. These populations and their parents were evaluated in the 2009 season in the experimental field in Capão do Leão, RS, Brazil. The higher values of mean squares associated to GCA indicates a strong contribution of additive genetic effects to the expression of grain chemical components. The parents tested showed a tendency to develop progeny with negative heterosis regarding protein, lipid, β-glucan and soluble dietary fiber in the grain, and positive for the content of nitrogen-free extract, total and insoluble dietary fiber. IAC 7 features a potential parent for obtaining grains with high protein and dietary fiber content, and low caloric content, fit to human diet. Meanwhile, UPF 15 and FAPA Louise can represent donors of alleles to increase lipid contents, while FAPA Louise and URS Guapa can be used to raise the grain nitrogen-free extract contents of lines intended for animal feeding.     

Feasibility of selection for traits associated with cold tolerance in rice under rapid generation advance method

Summary Variability of the hybrid population can be preserved through generations during the process of rapid generation advance (RGA). Effective selection can be done in an early generation for those traits having high heritability value like growth duration and plant height. But selection is not advantageous for traits having low heritability. Thus, selection for panicle exsertion, cold tolerance at seedling stage and panicle length would not be wise during the early generations. However, in the low temperature areas growth duration and plant height are two important factors which determine varietal suitability. As selection of these two characters are possible through RGA, it should be a standard parctice during RGA to eliminate the plants with long growth duration and select plants with optimum plant height.     

Identification of QTLs controlling rice drought tolerance at seedling stage in hydroponic culture

‘Drought avoidance’ and ‘drought tolerance’ are two mechanisms by which plants adapt under water stress. These mechanisms are difficult to evaluate separately in field experiments. Using hydroponic culture, we studied the genetic control of drought tolerance in rice (Oryza sativa L.) without the effect of drought avoidance. A backcross inbred population of ‘Akihikari’ (lowland cultivar) × ‘IRAT109’ (upland cultivar) with 106 lines was cultured with (stressed condition) and without (non-stressed condition) polyethylene glycol (PEG) at seedling stage. The relative growth rate (RGR), specific water use (SWU), and water use efficiency (WUE) showed significant genotype × environment interactions with or without PEG, indicating that each line responded differently to water stress. A quantitative trait locus (QTL) analysis revealed that these interactions were QTL specific. A total of three QTLs on chromosomes 2, 4, and 7 were detected for RGR. The QTL on chromosome 7 had a constant effect across environments, while the QTL on chromosome 4 had an effect only under non-stressed condition and that on chromosome 2 only under stressed condition. The stress-specific QTL on chromosome 2 was not co-located with any QTLs for root system depth previously reported from the same mapping population. However, this QTL was co-located with a stress-specific QTL for SWU, suggesting that the control of transpiration was relevant to dry matter production under drought. We concluded that PEG-treated hydroponic culture is very effective for use in genetic analyses of drought tolerance at seedling stage.     

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

Summary 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.Concentrations of palmitate and linolenate decreased moderately over cycles of selection, whereas stearate content increased. A major increase occurred in the content of oleate and a major decrease in linoleate. Most of the modification of fatty acid composition took place within the saturated and unsaturated classes. The ratio of unsaturated to saturated fatty acids increased over cycles of selection. Significant genetic variation was present for each fatty acid, indicating that selection for different desired fatty acid compositions in groat oil of oat should be possible in this population.Abbreviations GO groat-oil content - 16:1 palmitate - 18:0 stearate - 18:1 oleate - 18:2 linoleate - 18:3 linolenate     

燕麦种子贮存后遗传完整性研究

本文取材青海农林科学院１９５６、１９６４、１９８４年存入西宁自然库中裸燕麦和皮燕麦种子共１２个品种，于１９３９年从生理生化、细胞学等进行了多项指标的测定和分析，结果表明：贮存８年的种子发芽率高，平均发芽率裸燕麦８５．０％，皮燕麦７４．１％，其幼苗鲜重、干重，活力指数、ＴＴＣ活性等均高，而电导率低；贮存２８年的种子发芽率明显降低，平均发芽率裸燕麦为４８．２％，皮燕麦为２．０％；贮存３６年的种子已丧失     

Signatures of divergent selection for cold tolerance in maize

Divergently selected genotypes can be used for detecting the genomic regions affecting the selected trait (selection signature). Moreover, the genetic distances (GDs) among divergently selected lines can be correlated with the agronomic performances of the crosses among them. Using as source the maize F₂ of B73?×?IABO78, we previously conducted four cycles of divergent recurrent selection and three cycles of divergent selection in inbreeding for cold tolerance at germination. We finally obtained 10 lines selected for low (L) and 10 lines selected for high (H) cold tolerance, which exhibited a notable divergence for both the selected and associated traits. Herein, we investigated the 20 lines and the 28 single diallel crosses among eight random lines (four L and four H); the main objectives were to identify the putative regions controlling the selected and associated traits and to study the relationships between crosses performances and GDs among their parental lines. Allele frequencies at 932 recombination blocks based on 19,220 polymorphic SNPs were obtained for the two lines’ groups; the F _ST calculated across sliding windows indicated 18 regions highly divergent between groups. The increasing alleles for cold tolerance were contributed by both parents, consistently with the transgressive segregations previously found. Several regions associated to DG also affected various agronomic traits. The cross performances showed some relationships with the genetic distances among parental lines for traits affected by dominance, provided that all crosses were considered, while these relationships vanished when only L?×?H crosses were examined.     

Assessment of techniques for screening alfalfa cultivars for aluminum tolerance

Screening toxicity tests are an effective method to characterize aluminum tolerant plants. In this paper, three screening procedures were used to assess aluminum tolerance among 13 cultivars of alfalfa (Medicago sativa L.). The procedures used were: Petri dish screening, black glass plot method and the soil-on-agar procedure. Major biological indices used to analyze aluminum tolerance were relative root length (RRL), relative germination rate (RGR), relative hypocotyl length (RHL), relative fresh weight (RFW) and root emergence (RE). Aluminum negatively affected all five indices. A Pearson correlation test indicated that the results of the three screening procedures were consistent, suggesting that all three could be used for screening purposes. However, because of the short test period and the simplicity of operation, the black glass plot method might be the best choice. Overall, cv. Super No. 7 and WL-525HQ were the most aluminum-tolerant alfalfa cultivars, while Pondus S was the most sensitive.     

Evaluation of 'Anahuac' wheat mutant lines for aluminum tolerance

Seeds from the aluminum sensitive cultivar ‘Anahuac’ were treated by gamma-ray radiation. Twenty eight selected Al⁺³ tolerant mutants were compared to the original Anahuac and the tolerant wheat cultivars IAC-24 and IAC-60 from 1994 to 1996 in acid (Capão Bonito) and limed (Monte Alegre do Sul and Tatui) soil field trials. Grain yield and agronomic characteristics were analyzed. Twenty six mutant lines yielded higher than the sensitive Anahuac cultivar in the acid soils of Capão Bonito. Under limed soil conditions, the mutants had a similar yield to the original sensitive cultivar. The majority of the mutants were similar in yield to the tolerant cultivars IAC-24 and IAC-60 under both conditions. Some of the mutants showed altered agronomic characteristics but even in these cases this will not limit its utilization. The results indicated that tolerant lines with good characteristics may be obtained from a susceptible cultivar by mutation induction, thus allowing cropping in conditions where Al⁺³ is a limiting factor.