Wild Oryza species as potential sources of drought-adaptive traits

Wild species of Oryza may serve as sources of superior drought tolerance alleles for cultivated rice. In a series of three screenhouse experiments, we compared traits associated with leaf water status, stomatal conductance, membrane stability, and root development in several wild Oryza accessions and O. sativa cultivars, when grown under well-watered or water-deficient conditions. One accession of O. longistaminata had greater stomatal conductance under stress and maintained leaf elongation better under stress than most other genotypes. Several upland-rice cultivars from the japonica subspecies also maintained greater conductance and leaf expansion than an indica cultivar or O. rufipogon accessions. Leaves of an accession of O. latifolia were particularly sensitive to water deficit. Oryza longistaminata and several O. rufipogon accessions had greater membrane stability, measured as electrolyte leakage from leaf disks after heat treatment, than cultivated rice. Drought treatments tended to reduce the levels of electrolyte leakage observed. Wild species had levels of osmotic adjustment under stress that were similar to O. sativa. Entries differed in the growth of roots with water deficit:O. longistaminata accessions and some japonica cultivars showed either an increase in total root mass or an increase in the proportion of root mass in deeper soil levels when water deficit was imposed, whereas indica cultivars and O. rufipogon accessions did not. Changes in root mass and distribution were correlated with values of stomatal conductance and leaf elongation; this suggests that leaf measurements made at key times in the drying cycle may reveal possible genetic differences in rooting behavior, which are otherwise difficult to measure. These studies indicate that O. longistaminata and O. rufipogon may serve as sources of novel alleles for improved leaf traits under drought stress–specifically, for maintenance of leaf elongation, stomatal conductance, and membrane stability. Alleles for improved root growth and distribution under water deficit exist in some japonica rice cultivars.     

食用向日葵产量与籽粒主要性状配合力及遗传分析

选用4份分枝型恢复系和6份雄性不育系材料作亲本,按照不完全双列杂交（NCII）设计配制24份向日葵杂交组合,对组合的小区产量、单株产量、单盘实粒数、百粒重、籽仁率、籽粒长度和籽粒宽度7个性状的亲本配合力、遗传参数及竞争优势进行分析。结果表明,24份组合的7个性状存在真实性的遗传差异。在亲本不育系一般配合力（GCA）选择的基础上,应注意组合特殊配合力（SCA）的选择,GCA效应值高的亲本育种潜力较大,组配出优势组合的概率大;籽粒长度和籽粒宽度的狭义遗传力较低,分别为7.91%和14.89%,不宜进行早代选择;GCA较高的不育系为亲本A和亲本D,其中亲本A在各性状上均为正向GCA效应值,且在供试不育系中,其GCA效应值最大,其次为亲本D;组合1×A小区产量的SCA效应值及竞争优势最高,为本试验中的最优组合,其他籽粒性状与对照相比也均有提升。     

Thermal phenotyping of stomatal sensitivity in spring barley

Thermometry and thermography are alternative methods used for measuring stomatal conductivity via transpirative cooling. However, the influence of mixed soil–plant information contained in thermal images compared to thermometric spot measurements on the measurement quality and relationships to agronomic traits remains unclear. To evaluate their respective influence, canopy temperature was measured simultaneously by two infrared thermometers (thermometry), which were oriented oblique to the plant canopy and mounted on a tractor, and a hand‐held, nadir oriented thermal camera (thermography) in irrigated and drought‐stressed spring barley cultivar trials in 2011. Canopy temperatures were separated from soil temperatures and extracted from the thermal images by matching thermal and RGB images. Thermometric measurements conducted at the beginning of shooting during a stable period of high radiation were more closely related to total plant biomass and straw yield at harvest than thermography under both irrigated and drought‐stressed conditions. Taking into account the results of this evaluation, thermometry was used for assessing the agronomic importance of stomatal sensitivity, the earliness of stomatal closure, of spring barley cultivars subjected to different water supply in 2013. In this year, 16 spring barley cultivars were grown under mild drought stress and rainfed conditions. A stomatal sensitivity index was derived relating canopy temperatures of the cultivars grown under rainfed and drought‐stressed conditions to each other. Under rainfed conditions, stomatal sensitivity was negatively related to grain protein yield with a coefficient of determination of R² = .43. Under increasing terminal drought stress, positive regression slopes of stomatal sensitivity to grain yield, biomass yield and culms/m² were observed with coefficients of determination amounting to R² = .22, .31 and .36, respectively. Stomatal sensitivity negatively impacts agricultural production under well‐watered conditions, but maintains productivity under conditions of terminal drought.     

Old and New Cultivars of Soya Bean (Glycine max L.) Subjected to Soil Drying Differ in Abscisic Acid Accumulation,Water Relations Characteristics and Yield

Two old (Huangsedadou and Longxixiaohuangpi (LX)) and two new (Jindou 19 (JD) and Zhonghuang 30 (ZH)) soya bean (Glycine max (L.) Merr.) cultivars were used to investigate the influence of soil drying on the abscisic acid (ABA) accumulation in leaves, stomatal conductance (g_s), leaf water relations, osmotic adjustment (OA), leaf desiccation tolerance, yield and yield components. The greater ABA accumulation was induced by soil drying, which also inducing g_s decreased at higher soil water contents (SWC) and leaf relative water content (RWC) significantly decreased at lower SWC in the new soya bean cultivars than in the old soya bean cultivars. The soil water threshold between the value at which stomata began to close and the RWC began to decrease was significantly broader in the new cultivars than in the old cultivars. The new cultivars had significantly higher OA and lower lethal leaf water potential than old cultivars when the soil dried. The old cultivars had greater biomass, but lower grain yield than the new cultivars in well‐watered, moderate stress and severe stress conditions. Thus with soil drying, the new soya bean cultivars demonstrated greater adaptation to drought by inducing greater ABA accumulation, stomatal closure at higher SWC, enhanced OA and better water relations, associated with increased leaf desiccation tolerance, greater water use efficiency and higher yield.     

Genetic effects on biomass yield in interspecific hybrids between Brassica napus and B. rapa

This study was conducted to estimate the genetic effects on biomass yield in the interspecific hybrids between Brassica napus and B. rapa, and to evaluate the relationship between parental genetic diversity and its effect on biomass yield of interspecific hybrids. Six cultivars and lines of oilseed B. napus and 20 cultivars of oilseed B. rapa from different regions of the world were chosen to produce interspecific hybrids using NC design II. Obvious genetic differences between B. rapa and B. napus were detected by RFLP. In addition, Chinese B. rapa and European B. rapa were shown genetically differences. Plant biomass yield from these interspecific hybrids were measured at the end of flowering period. Significant differences were detected among general combining ability (GCA) effects over two years and specific combining ability (SCA) effects differences were detected in 2000. The ratios of mean squares, (σ² _GCA(f) + σ² _GCA(m)) / (σ² _GCA(f) + σ² _GCA(m) + σ² _SCA), were 89% and 88% in 1999 and 2000, respectively. This indicates that both additive effects and non-additive effects contributed to the biomass yield of interspecific hybrids and the former played more important role. Some European B. rapa had significant negative GCA effects while many of Chinese B. rapa had significant positive GCA effects, indicating that Chinese B. rapa may be a valuable source for transferring favorable genes of biomass yield to B. napus. Significant positive correlation between parental genetic distance and biomass yield of interspecific hybrids implies that larger genetic distance results in higher biomass yield for the interspecific hybrids. A way to utilize interspecific heterosis for seed yield was discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Wurzelsystem, Biomasseproduktion, Bestockung und Ertragsbildung von vier Winterweizensorten in einem System mit geringer Betriebsmittelzufuhr von außen

Rooting patterns, biomass production, tillering, and yield formation of four winter wheat cultivars in a low external input system Growth conditions of winter wheat in agricultural low external input systems, e.g. ecological agriculture differ from those in conventional agriculture with regard to nutrient flow, impact of diseases, and weed competition. Knowledge of the dynamics of yield formation of winter wheat cultivars is very important for further development of such systems. During two growing seasons root growth, above ground biomass production, tillering, and yield formation were studied with four winter wheat cultivars of different periods of release at two ecologically managed farms in Northern Hessia. The results can be summarized as follows: – In general, plant breeding did not lead to a reduced development of root systems or above ground biomass production in winter wheat (Stöppler et al. 1989 a). Modern wheat varieties develop an extensive root system in greater depth, which means better drought resistance. – Not only root length densities, total root length, characteristics of tillering, and yield formation showed clear genotypic differences between the winter wheat cultivars, but also the development of root systems and above ground biomass production. – Winter wheat cultivars with a high plant density seem to have a retarded root growth after tillering due to intra-plant-competition and late root growth during grain filling, whereas cultivars with a high ear weight develop an extensive root system before the grain filling period. At the beginning of this period, a great root length per culm seems to be most important to achieve a high ear weight. The results indicate that those cultivars with poor to medium tillering and high ear weight are very well adapted to the reduced nutrient flow in low external input systems of farming. –In low external input systems, a satisfactory wheat crop need be established before tillering.     

Understanding physiological and morphological traits contributing to drought tolerance in barley

Drought stress is a major limiting factor for crop production in the arid and semi‐arid regions. Here, we screened eighty barley (Hordeum vulgare L.) genotypes collected from different geographical locations contrasting in drought stress tolerance and quantified a range of physiological and agronomical indices in glasshouse trails. The experiment was conducted in large soil tanks subjected to drought treatment of eighty barley genotypes at three‐leaf stage and gradually brought to severe drought by withholding irrigation for 30 days under glasshouse conditions. Also, root length of the same genotypes was measured from stress‐affected plants growing hydroponically. Drought tolerance was scored 30 days after the drought stress commenced based on the degree of the leaf wilting, fresh and dry biomass and relative water content. These characteristics were related to stomatal conductance, stomatal density, residual transpiration and leaf sap Na, K, Cl contents measured in control (irrigated) plants. Responses to drought stress differed significantly among the genotypes. The overall drought tolerance was significantly correlated with relative water content, stomatal conductance and leaf Na⁺ and K⁺ contents. No significant correlations between drought tolerance and root length of 6‐day‐old seedling, stomatal density, residual transpiration and leaf sap Cl^? content were found. Taking together, these results suggest that drought‐tolerant genotypes have lower stomatal conductance, and lower water content, Na⁺, K⁺ and Cl^? contents in their tissue under control conditions than the drought‐sensitive ones. These traits make them more resilient to the forthcoming drought stress.     

Forage yield potential of alfalfa plants of varying crown size from old stands

Alfalfa (lucerne) plants can persist from one growing season to the next because of their perennial crowns. Plants with large crowns often are selected for breeding purposes. The objective of this study was to determine the forage yield potential of plants with a full range of crown sizes sampled from old stands. This was accomplished by field evaluation of clones and S₁ progenies derived from plants of different crown sizes obtained from a 1 m² of 5-year-old stands of cultivars ‘Agate’ and ‘Magnum III’. Significant differences (P < 0.05) in dry forage yield (DFY) were found among entries in both tests. However, there was no consistent trend in DEY with respect to the crown size of the parental plants. Although the crown of space-planted clones dug after 16 months showed a strong association (r > 0.7, P < 0.01) with DFY, the crown size of these clones was poorly correlated with the crown size of their parental plants. These results suggest that selections based on crown size from older stands may not lead to an improvement in either crown size or forage yield. Crown health will remain an important selection criterion when plants are sampled from old stands; crown size, however, may not be as important.     

普通小麦籽粒DON含量的配合力分析

为了选育抗赤霉病且籽粒毒素含量低的小麦品种以减轻赤霉病危害,在对我国南方麦区地方品种进行赤霉病抗性鉴定的基础上,选用8个籽粒中脱氧雪腐镰刀菌烯醇（deoxynivalenol, DON）含量水平不同的小麦品种作亲本,按8×8半双列杂交配制28个杂交组合,以接种后成熟籽粒中DON含量、病小穗数、病小穗率和病粒率为指标,进行赤霉病抗性、一般配合力（GCA）和特殊配合力（SCA）遗传分析,以及不同鉴定指标间比较和相关性分析。结果表明,8个品种中籽粒DON含量以苏麦3号最低(0.5715 mg kg^-1),Alondra’s最高(13.5560 mg kg^-1),各组合F1的籽粒DON含量均低于感病品种Alondra’s。品种间GCA和SCA存在显著差异,籽粒DON含量以加性效应为主,存在部分显性效应。苏麦3号、望水白和翻山小麦表现出较好的一般配合力效应。以苏麦3号为亲本的5个组合、望水白为亲本的4个组合特殊配合力效应较大。扬麦158一般配合力效应较小,但有4个组合表现较好的特殊配合力效应。籽粒DON含量和病小穗数、病小穗率、病粒率呈极显著的正相关关系。感病品种Alondra’s和绵阳8545的各个抗性鉴定指标的一般配合力在8个品种的排序中表现一致,抗病品种各个抗性指标的一般配合力在8个参试材料间的排序有所差异。DON含量的狭义遗传力为74.54%,因此以抗DON积累为指标的赤霉病抗性育种,可以在早期世代进行选择。     

Inheritance of Corolla Size, Number of Stamens and Percentage of Plants with Petaloid Stamens in Evergreen Azaleas (Rhododendron Subsect. obtusa)

Research has been carried out on the inheritance of corolla size, number of stamens and percentage of plants with petaloid stamens (double flower) in evergreen azaleas (Rhododendron Subsect. obtusa). For this purpose two incomplete diallel crosses were used. The first one included seven species and one cultivar and the second diallel 13 cultivars. In both diallels for all three characters the GCA mean squares were high. Also, the positive correlation between the parental values and the GCA estimates for flower size and number of stamens indicates that the expression of these characters is mainly determined by additive gene action. A negative correlation was found between GCA estimates for die n number of stamens and the percentage of plants with petaloid stamens. When breeding azaleas with large double flowers, parents can be directly selected on the basis of these characters since additive genetic variance dominates. As no genetic correlations were found between corolla size and number of stamens (percentage of plants with petaloid stamens) the breeding will not be hampered by unfavourable linkage of genes for these characters.     

Prediction of genetic value for coffee production in Coffea arabica from a half-diallel with lines and hybrids

Genetic analysis of yield and morphological traits has been carried out in Coffea arabica from a half-diallel including the parental lines. The trial was established in west Cameroon with completely randomized single-tree plots. Observations included yield (four years), stem diameter, height and number of primaries. General combining abilities (GCA) and specific combining abilities (SCA) as heritabilities and genetic correlations were estimated. A significant SCA variance was observed for all the traits. Morphological traits, stem diameter, plant height and number of primaries, were genetically correlated to the yield. The hybrids were, on average, better performing than lines. There was no clear relationship between performance of lines and their general combining ability. Contribution of the seven lines to the SCA sum of squares was shown to be unequal for all the studied traits, one parent (Java) being far the most interactive. This variation of interactivity seemed to be related to different levels of residual heterozygosity among parental lines. Indirect prediction of yield using morphological traits gave the same value for expected genetic gain as the prediction based on cumulated yield over four years. The multitrait indirect selection for yield operated in a different way as far as GCA and SCA are concerned. The application of these results to coffee breeding strategies involving hybrid selection is discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Breeding value of selected blackcurrant (<Emphasis Type="Italic">Ribes nigrum</Emphasis> L.) genotypes for early-age fruit yield and its quality

The study was conducted in the years from 2011 to 2013 at the Research Institute of Horticulture in Skierniewice, Poland. The aim of the research was to assess the breeding value, based on the effects of general and specific combining abilities (GCA and SCA), of 15 parental genotypes of blackcurrant in terms of fruit yield and quality. The plant material consisted of F₁ generation seedlings obtained by crossing, in a factorial mating design of twelve maternal (‘Bona’, ‘Big Ben’, ‘Chereshnieva’, Kupoliniai’, ‘Gofert’, ‘Tines’, ‘Sofievskaia’, ‘Tihope’, ‘Ores’, ‘Ruben’, ‘Titania’ and D13B/11) and three paternal cultivars (‘Ceres’, ‘Foxendown’ and ‘Saniuta’). It was found that the cultivars ‘Ruben’, ‘Big Ben’, ‘Gofert’ and D13B/11 had significant positive effects of GCA on fruit yield at least in two consecutive years. ‘Ruben’, ‘Saniuta’ and D13B/11 had positive GCA effects on fruit weight. For ‘Chereshnieva’, ‘Gofert’, ‘Tines’, ‘Sofievskaia’, ‘Tihope’, ‘Titania’, ‘Ceres’ and Saniuta’ positive GCA effects were estimated for soluble solids content, whereas ‘Ruben’, ‘Ceres’, ‘Gofert’ and ‘Ores’ had positive GCA effects on the ascorbic acid content in fruit. This indicated a high breeding value of these parental genotypes in terms of the evaluated traits. The significantly positive values of SCA, estimated for the crossing combinations: ‘Big Ben’?×?‘Saniuta’, ‘Ruben’?×?‘Foxendown’, ‘Titania’?×?‘Ceres’, ‘Kupoliniai’?×?‘Saniuta’, ‘Gofert’?×?‘Foxendown’, ‘Gofert’?×?‘Saniuta’, ‘Tines’?×?‘Ceres’ and ‘Tihope’?×?‘Foxendown’ for at least two traits describing fruit yield and quality, were evidence of the interaction of both these parental genotypes in the creation of new dessert-type cultivars of blackcurrant.     

Combining ability for yield,protein and oil of peanut lines from South American centers of diversity

Summary Ten peanut (Arachis hypogaea L.) lines, two from each of five centers of diversity in South America, and the F₂ generation of all possible crosses among them were used to characterize the variation for yield, fruit and seed traits and protein and oil content and to determine the breeding potential of the parents. Two of the parental lines belong to subspecies hypogaea and the other eight to subspecies fastigiata.Several crosses gave heterotic responses for yield. The parents of the crosses with significant heterosis generally came from different centers of diversity.Variation among both general and specific combining abilities was significant for all traits with the exception of the SCA estimate for protein percent. The component of variation for GCA was larger than the SCA component for all traits.A Spanish line and a Valencia-like intermediate line from the Guarani region had the highest GCA effects for fruit yield, seed yield and meat content and transmitted consistently their characteristics to their F₂ progeny. Some lines showed significant but small maternal effects for oil, protein and oil + protein percent. Differences between reciprocal crosses were significant for fruit length, fruit weight and oil + protein percent.A significant portion of the variation among crosses was explained by differences among parental lines within centers of diversity. This supports the fact that centers are founded because of the diversity of the peanuts grown there.The performance of parental lines per se was useful in predicting the performance of the lines in hybrid combination for all traits except fruit yield.Paper number 6141 of the Journal Series of the North Carolina Agricultural Research Service (USA). This work was partially supported by CSRS Research Agreement 701-15-51.     

Combining ability for beet armyworm, Spodoptera exigua, resistance and horticultural traits of selected Lycopersicon pennellii-derived inbred backcross lines of tomato

Ten selected inbred backcross lines (IBL), from a Lycopersicon esculentum cv.‘Peto 84’×Lycopersicon pennellii IBL population, with resistance to beet armyworm (BAW), Spodoptera exigua, higher fruit mass and fruit yield, were crossed with eight elite cultivated L. esculentum inbred lines in a Design II mating design. Three elite inbreds were also crossed to ‘Peto 84′, the IBL recurrent parent, as a control for combining ability. Field plots of all resulting F₁ progenies and control cultivars were inoculated with BAW eggs and evaluated for resistance to BAW, fruit mass, fruit yield, vine size and maturity at three field locations. Reductions in fruit damage by BAW were found in four of the 10 IBL F₁ progenies. Significant male and female general combining ability (GCA) estimates for BAW resistance were observed, but significant specific combining ability for BAW resistance was not detected. The fruit mass of F₁ hybrids was significantly lower than large-fruited controls, but was not significantly different from elite inbred by ‘Peto 95’F₁ hybrids. Selection based on inbred performance identified IBL with positive GCA for BAW resistance and yields in Design II hybrids. BAW resistance in the 09 selected IBL and IBL- derived F₁ progeny was associated with two undesirable traits, later maturity and larger vine size. Index selection of IBL was more effective at identifying IBL with positive GCA for fruit mass and fruit yield than GCA for BAW resistance.     

Evaluation of a lucerne germplasm collection in relation to traits conferring grazing tolerance

Summary A collection of 90 accessions of different germplasm groups from the Medicago sativa complex was evaluated at Lodi, Italy, for dry-matter yield, time to anthesis, height of regrowth, plant diameter, stem density, vegetative recovery after winter, and presence of deep-set crown and ability to spread with creeping roots or rhizomes, these latter characters possibly contributing to grazing tolerance. The germplasm groups proved rather distinct for these traits, but all included types potentially suitable for grazing. Interesting types combining deep-set crown and high yield occurred mainly in subsp. x varia and materials originated from artificial crosses involving at various extent the subspecies falcata, sativa and x varia. Though belonging to subsp. sativa, mielga wild populations from Spain had aerial traits similar to those of the long-dormant, low-yielding subsp. falcata. Deep-crowned plants had greater plant diameter than shallow-crowned plants, and could be categorised into four distinct top-growth models according to their habit and vigour. One of these models combined spreading ability with high yield. The about 150 plants selected for their combination of deep crown, wide diameter, and good yield were characterised by a branch-rooted system. There was general correspondence between top-growth and root morphology of each model. Of the four deep-crowned models, three had rhizomes, with wide range of underground development and morphology, while the fourth had creeping roots. The latter model was the most rare among the examined accessions, never appearing in either cultivated or wild subsp. sativa. The implications of the results on the development of grazing-tolerant lucerne varieties are discussed.     

Efficiency in the use of phosphorus,nitrogen and potassium in topless faba beans (Vicia faba L.) – variability and inheritance*

In a field experiment with topless faba beans, parental inbred lines and FI hybrids of a 7 × 7-diallel were evaluated for traits related to the P, N and K efficiency. In addition, the parental inbreds were cultivated in a pot experiment at two P levels (100 vs. 700 mg P per pot). Significant heterosis for grain yield, uptake and utilization efficiency of nutrients in the field experiment highlighted the enhancement of nutrient efficiency in the hybrids. Amongst both parental inbreds and hybrids, significant genotypic variation was found for nearly all recorded traits. In the diallel analysis, the GCA effects generally proved to be highly significant and in most cases considerably higher than the SCA effects. In the pot experiment, grain yield ranking of the parental lines at the high P level (= P700) was very similar to that in the field experiment, whereas at the low P level (= P100, – P deficiency) the ranking of the lines changed considerably. Correspondingly, the P level-line interaction was highly significant. High tolerance towards P deficiency was found for those two parental inbreds derived from cultivars bred under Syrian conditions. At the high P supply, P efficiency was more favoured by a high P uptake, but at P deficiency by a high internal P utilization.     

Diallel analysis of barley for resistance to leaf stripe and impact of the disease on genetic variability for yield components

Barley breeders in Syria attempting to develop barley (Hordeum vulgare L.) cultivars resistant to barley leaf stripe (BLS) disease caused by Pyrenophora graminea Ito & Kuribayashi [anamorph Drechslera graminea (Rabenh. Ex. Schlech. Shoem.)]. Information on the combining ability for BLS resistance in Syria is not available. This study was conducted to evaluate, in 10 genetically diverse barley parents, general combining ability (GCA) and specific combining ability (SCA) effects towards the determination of the genetic basis of disease resistance and to estimate genetic variability for yield components and its modification by BLS. Ten parental genotypes varying in their reactions to BLS were crossed in a half-diallel mating design to generate 45 full-sib families. The families and the parents were inoculated with P. graminea and evaluated for resistance in replicated field tests (three inoculated and three non-inoculated plots). The parents chosen showed wide variations for resistance to BLS. Genetic component analysis showed significant effects for both GCA and SCA for resistance to BLS, suggesting that additive as well as non-additive genetic mechanisms were involved in the expression of resistance in these parents. GCA effects were more important than SCA effects. Resistant parents exhibited high negative GCA indicating that additive gene effects were more predominant, and suggesting their prime suitability for use in barley breeding programs to improve resistance to BLS. Narrow-sense heritability was 58% and broad-sense heritability was 99% indicating that selection for BLS resistance should be effective in these crosses. A high genetic variability for the agronomic traits studied was observed. Yield components decreased significantly in inoculated plants and more pronounced in diseased plants. Significant GCA was observed for all traits. Values for GCA were, in some cases, significantly modified by BLS. This indicates that attention must be paid to the danger of drawing conclusion in quantitative genetics studies dealing with both diseased and healthy plants. Two genotypes, Banteng and Igri, had high negative GCA effects and are promising parents for enhancement of BLS resistance.     

遮阴对黄淮海玉米主栽品种农艺性状和产量的影响

为分析遮阴对黄淮海玉米主栽品种农艺性状、产量性状和产量的影响,以黄淮海种植面积最大的10个玉米品种为材料,种植在该地区4个省（市）,并设抽雄前遮阴7天和全生育期不遮阴2个处理。研究结果表明遮阴处理对黄淮海玉米主栽品种农艺性状、产量性状及产量均具有显著的影响,10个品种产量均显著的降低,6个品种抽雄吐丝间隔期延长,9个品种吐丝率下降;遮阴后产量降低与行粒数、穗长、穗粗、百粒重变小,秃尖变大有显著的相关性;‘伟科702’在10个品种中耐阴性最好,遮阴后4地点平均产量第一,吐丝率和产量降幅最低,其次为‘郑单958’、‘蠡玉16’和‘隆平206’。因此,生产上应选‘伟科702’等耐阴性较好的品种,耐阴育种方面应将行粒数、穗长、穗粗、百粒重、秃尖长度、吐丝率和抽雄吐丝间隔期等显著相关的性状作为耐阴性鉴定的指标。     

Combining ability and correlations for yield components in early generations of potato breeding

A partial diallel set of crosses was made between 14 potato cultivars chosen for their fertility, from those included in a potato breeding programme at the NEIKER – Basque Institute for Agricultural Research. The progeny were grown in completely randomized trials from 1997 to 1999. Performance for yield, tuber number and average tuber weight was analysed in seedling and two clonal generations. Variance estimates due to both general combining ability (GCA) and specific combining ability (SCA) were significant in all generations for all traits under study. However, SCA was more important than GCA in almost all cases. Correlation coefficients among characters, generations, GCA and SCA effects were examined. For tuber yield no relation was obtained between generations; however, average tuber weight and yield were positively associated in all generations. The results indicate that appropriate selection criteria depend strongly on the particular cross. The implication for a breeding strategy are discussed.     

Combining ability for seed yield traits of Chenopodium quinoa breeding lines

For a better understanding of the inheritance of seed yield traits in Quinoa (Chenopodium quinoa) Willd., a half-diallelic crossing experiment with six diverse but uniform breeding lines was conducted. True hybrid plants were detected by means of differences in panicle colour in 14 out of the 15 crosses performed. The agronomic performance of 14 F₂ populations and six parental lines was evaluated in field trials on fertile clay soil. General and specific combining ability of the lines (GCA and SCA) were estimated. Highly significant differences in GCA effects were found between the lines for plant height at maturity, early flowering, early maturity, seed yield and thousand seed weight. Significant SCA effects were only found for plant height at maturity. However, SCA effects were rather small and accounted for 7% of the total variance. The finding of large GCA effects and low SCA effects suggests that best selection results could be expected from crosses between the agronomic best performing genotypes. This revised version was published online in August 2006 with corrections to the Cover Date.