Effects of photoperiod sensitivity genes Ppd‐B1 and Ppd‐D1 on spike fertility and related traits in bread wheat

Increasing grain yield is a key breeding goal in bread wheat. Several authors have suggested that a spike fertility index (SF), that is the quotient between grain number per unit spike (GNS) and spike chaff dry weight (SCDW), could be used as a yield‐related selection criterion, especially if molecular markers were available. Here, the effects of Ppd‐B1 and Ppd‐D1 genes on SFm, GNSm and SCDWm (measured at maturity) and the relationship between these variables were analysed in field experiments carried out during three crop seasons at Balcarce, Argentina, on an association mapping population of 100 bread wheat cultivars of diverse origin released in Argentina between 1927 and 2010. Results show that both Ppd‐B1 and Ppd‐D1 are associated with SFm with similar effects. Cultivars with insensitive alleles at both genes showed a mean SFm 9.2% greater than those with sensitive alleles at both genes; at each gene, difference in SFm between insensitive and sensitive alleles was ~4.5%. In turn, each gene showed a differential effect on GNSm and SCDWm, as Ppd‐B1 was more related to SCDWm, whereas Ppd‐D1 was only related to GNSm. Although more research needs to be carried out in order to ascertain the physiological pathway by which these genes affect spike fertility, this study represents a first approximation in order to elucidate the molecular and genetic basis underlying SF and related physiological traits.     

Variation for nitrogen use efficiency traits in current and historical great plains hard winter wheat

Wheat genotypes that efficiently capture and convert available soil nitrogen into harvested grain protein are key to sustainably meeting the rising global demand for grain protein. The purposes of this study were: to characterize the genetic variation for nitrogen use efficiency (NUE) traits within hard winter wheat adapted to the Great Plains of the United States and evaluate trends in the germplasm with year of release; to explore relationships among traits that may be used for selection within breeding programs; and to identify quantitative trait loci associated with NUE traits in this germplasm. NUE traits were measured in a panel of 299 hard winter wheat genotypes, representing historically important and contemporary germplasm, from across the growing region. Trials were grown in two years at two levels of nitrogen fertility. Genotype and genotype × year interaction effects were highly significant for NUE traits, while genotype × nitrogen rate interactions were non-significant. Strong genetic correlations of plant height and flowering date with NUE traits were observed. Wheat breeders have improved NUE: the subset of 183 genotypes that were released as cultivars after 1960 demonstrated significant trends with year of release for improved grain N yield, grain yield, nitrogen harvest index, nitrogen uptake efficiency, nitrogen utilization efficiency, and post-anthesis nitrogen uptake. In genome-wide association analyses, plant height and flowering date were important covariates in the mixed models, and plant height and flowering date substantially explained the variation in NUE traits in this germplasm. Marker-trait associations were identified that may prove useful in breeding.     

黄淮海麦区四省份小麦品种的农艺性状及遗传多样性分析

小麦品种的遗传多样性在育种工作中发挥着重要的作用。为了明确黄淮海麦区四省份小麦品种遗传多样性的基础,本研究以所收集的黄淮海麦区的河南、河北、山东和陕西四省的近十几年来(1992-2008年)审定的部分(42份)小麦品种为研究材料,以9个农艺性状为基础进行遗传性状的分析。结果表明,不孕小穗数的变异系数最大为61.39%,其次为有效分蘖和穗粒数,千粒重的变异系数最小为6.06%。河南、河北、山东和陕西四省的多样性指数分别为1.83,1.82,1.73和1.62,平均值为1.75。在此基础上,用最长距离法可将42份材料聚为三大类,但是第Ⅱ大类和第Ⅲ大类相差不大,这说明上述四省小麦品种遗传多样性在逐步提高的同时,其遗传基础仍需进一步拓宽。在性状选择上,首先对变异大的性状进行选择是非常重要的;在品种选择上,应注意选择产量、单株粒重和单株粒数均高的品种。     

The Potential of Using Spectral Reflectance Indices to Estimate Yield in Wheat Grown Under Reduced Irrigation

Summary The objectives of this research were to study the association in bread wheat between spectral reflectance indices (SRIs) and grain yield, estimate their heritability, and correlated response to selection (CR) for grain yield estimated from SRIs under reduced irrigation conditions. Reflectance was measured at three different growth stages (booting, heading and grainfilling) and five SRIs were calculated, namely normalized difference vegetation index (NDVI), simple ratio (SR), water index (WI), normalized water index-1 (NWI-1), and normalized water index-2 (NWI-2). Three field experiments were conducted (each with 30 advanced lines) in three different years. Two reduced irrigation environments were created: (1) one-irrigation level (pre-planting), and (2) two-irrigation level (pre-planting and at booting stage), both representing levels of reduced moisture. Maximum yield levels in the experimental zone were generally obtained with 4–6 irrigations. Genotypic variations for all SRIs were significant. Three NIR (near infrared radiation) based indices (WI, NWI-1, and NWI-2) gave the highest level of association (both phenotypic and genotypic) with grain yield under both reduced irrigation environments. Use of the mean SRI values averaged over growth stages and the progressive integration of SRIs from booting to grainfilling increased the capacity to explain variation among genotypes for yield under these reduced irrigation conditions. A higher level of broad-sense heritability was found with the two-irrigation environment (0.80) than with the one-irrigation environment (0.63). Overall, 50% to 75% of the 12.5% highest yielding genotypes, and 50% to 87% of the 25% highest yielding genotypes were selected when the NWI-2 index was applied as an indirect selection tool. Strong genetic correlations, moderate to high heritability, a correlated response for grain yield close to direct selection for grain yield, and a very high efficiency of selecting superior genotypes indicate the potential of using these three SRIs in breeding programs for selecting increased genetic gains in grain yield under reduced irrigation conditions.     

Genotype x environment interaction for durum wheat grain yield and selection for drought tolerance in irrigated and droughted environments in Iran

Durum wheat is grown in the Mediterranean region under stressful and variable environmental conditions. In a 4-year-long experiment, 14 genotypes [including 11 durum breeding lines, two durum (Zardak) and bread (Sardari) wheat landraces, and one durum (Saji) newly released variety] were evaluated under rainfed and irrigated conditions in Iran. Several selection indices [i.e. stress tolerance index (STI), drought tolerance efficiency (DTE), and irrigation efficiency (IE)] were used to characterize genotypic differences in response to drought. The GGE biplot methodology was applied to analyze a three-way genotype-environment-trait data. Combined ANOVA showed that the year effect was a predominant source of variation. The genotypes differed significantly (P < 0.01) in grain yield in the both rainfed and irrigated conditions. Graphic analysis of the relationship among the selection indices indicated that they are not correlated in ranking of genotypes. The two wheat landraces and the durum-improved variety with high DTE had minimum yield reduction under drought-stressed environments. According to STI, which combines yield potential and drought tolerance, the “Saji” cultivar followed by some breeding lines (G11, G8, and G4) performed better than the two landraces and were found to be stable and high-yielding genotypes in drought-prone rainfed environments. The breeding lines G8, G6, G4, and G9 were the efficient genotypes responding to irrigation utilization. In conclusion, the identification of the durum genotypes (G12, G11, and G4) with high yield and stability performance under unpredictable environments and high tolerance to drought stress conditions can help breeding programs and eventually contribute to increasing and sustainability of durum production in the unpredictable conditions of Iran.     

The relationship between the regeneration system and genetic variability in the cucumber (Cucumis sativus L.)

Durum wheat has been subjected to intense breeding in Italy due to its local economic importance. Four groups of Italian cultivars representative of different breeding eras were compared in northern Syria for yield potential and morphophysiological features at a moderately favourable site, and drought tolerance at a stressful site. Group 1 included indigenous landraces; Group 2 comprised genotypes selected from exotic landraces (released in 1920's–1930's); Group 3 included genotypes selected from crosses or mutagenesis involving Group 2 materials (1950's–1960's); Group 4 comprised genotypes selected from crosses between CIMMYT and Group 2 materials (from 1970's). Under moderately favourable conditions, a yield increase of 1.03 t ha–¹ was observed from Group 1 through Group 4, corresponding to a genetic gain of about 0.017 t ha–¹ per year. Such increase was only partly accounted for by a parallel increase in spike fertility and seed weight. Plant stature decreased dramatically from Group 1 to Group 4; a remarkable reduction of height was already attained in Group 3, before the introduction of dwarfing genes from bread wheat. Earliness of heading and grain filling duration increased consistently across breeding phases, the length of crop cycle remaining almost unaltered. No significant improvement of drought tolerance resulted from the breeding activity, suggesting the need to put more emphasis on selection for real stress tolerance rather than escape. Overall variation for morphophysiological traits, assessed by a principal components analysis, highlighted the great diversity among the Group 1 cultivars, while variation within Groups 3 and 4 was lower. Indigenous landraces, little used in the breeding history, as well as novel, unexploited exotic germplasm sources could contribute to broaden the crop genetic base in the region.     

耐旱耐热小麦新种质筛选及新品种选育

黄淮麦区水资源严重紧缺,人均、每公顷水资源占有量远低于全国平均水平。为了解决这些问题,培育出抗旱耐热的优良旱地小麦品种是最经济有效的技术措施。本研究通过多种途径平均收集旱地小麦种质资源500余份,经过生态指标观测及分子水平检测,筛选出目标性状优良并有较高遗传力的核心亲本。利用这些核心亲本,以常规杂交选育为主,结合分子标记辅助选择;生态育种与穿梭育种相结合;形态特征、生育特性与仪器指标测试相结合的育种方法,对后代材料进行抗逆性、节水性、优质性能和高产潜力的综合评价。最终育成‘运旱137’(晋审麦2016004)和‘运旱139-1’(晋审麦20170004)2个抗旱耐热的旱地小麦新品种及若干遗传基础丰富并具有特殊优良性状的中间材料。其中,‘运旱1411-2’、‘运旱1512’、‘运旱1818’、‘运旱1816’、‘运旱139-2’等已经参加了各类区域试验。本研究为其他育种者提供了参考,也为后续新品种的推广做好了准备。     

The Effect of Chromosome 1B/1R Translocation on the Yield Potential of Certain Spring Wheats (Triticum aestivum L.)

Nearly 50 percent of the 1988 advanced breeding lines of the CIMMYT bread wheat breeding program possess the 1B/1R homozygous translocation. Hence, a trial was conducted to estimate the effect of 1B/1R chromosome translocation on the yield potential of some of our high-yielding spring wheats, where non-limiting levels of fertility, moisture, preventive pest and disease programs were used. In conclusing the 1B/1R lines seemed to have increased their above-ground biomass yield, number of spikes per meter², 1000-grain weight and test weight. They also exhibited a slight advantage over the 1B homozygous lines on grain yield. The observed difference, however, was non-significant, as was the plant height difference observed among the two groups. Varietal comparisons indicated that the 1B/1R group headed later than the 1B group.     

Estimation of quantitative genetic parameters for grain yield and quality in winter wheat under high and low nitrogen fertilization

The main question connected with developing wheat cultivars adapted to low nitrogen (N) is whether separate breeding programs for low and high input conditions are necessary. Nineteen wheat cultivars were grown over three years in Croatia in a total of eight environments at high N and low N in order to determine the effect of two N levels on means, variances and heritability of grain yield and bread-making quality and to assess the relative efficiency of indirect selection under high N in improving trait means under low N. Means of grain yield and grain protein content decreased under low N 10 and 13 %, respectively compared to the high N, whereas higher reductions of means due to lower fertilization were observed for grain N yield (21 %), wet gluten content (20 %), Zeleny sedimentation value (27 %) and for most rheological parameters, whose mean values were reduced from 20 % to as much as 57 %. Heritabilities for grain yield and grain N yield at high N were 0.82 and 0.76, respectively, and 0.77 and 0.43 at low N. Heritability for dough development time, stability and resistance also tended to be higher at high N than at low N due to a decrease in genetic variance and an increase in error variance at low N. The genetic correlation coefficients between high and low N were higher than 0.90 and the efficiency of indirect selection under high N for performance under low N was near 1.0 for grain yield and for most bread-making quality traits.     

Early generation genetic variation and heritability of yield and related traits among tef populations

The extent of genetic variation and heritability of a trait are among the major determinants of selection gains in plant breeding programs. The aim of this study was to determine the magnitude of genetic variation and inheritance of grain yield, and component traits of newly developed tef populations under moisture-stressed and non-stressed conditions for drought tolerance breeding. Seventeen crosses along with the parents were evaluated in the F2 generation under moisture-stressed and non-stressed conditions in northern Ethiopia during 2015 and 2016. There were marked genotypic and phenotypic variation among the crosses in the F2 generation for plant height, panicle length, peduncle length, number of productive tillers per plant, main shoot panicle seed weight, biomass yield, and grain yield under both test conditions, important for successful selection and genetic advancement. The families of DZ-Cr-387 x 207832 and DZ-Cr-387 x 222076 were high grain yielders with early maturity under both test conditions.     

Genetic variation and interrelationships of agronomic characters in landraces of bread wheat from southeastern Iran

There is renewed interest in wheat landraces as important sources of genetic variation for agronomic characters. Fifty-three pure lines of bread wheat (Triticum aestivum L.) derived from seven landraces collected from southeastern Iran were used to estimate genetic variation and heritability for 13 developmental and quantitative characters. Path-analysis was used to partition the genetic correlations between grain yield and six grain yield-related traits. Mean values of landraces were also compared with three improved cultivars from California and Iran. Genotypic differences among the landraces and among the pure lines collected from the landraces were highly significant for all characters considered. Compared with the modern cultivars, the landrace genotypes were, on average, later in days to heading and taller than the cultivars but had lower values for number of grains per spike, 1000-grain weight, grain yield and harvest index. Some landrace genotypes were similar to the modern cultivars for grain yield. Moderate to high genetic variation was displayed by number of grains per spike, number of spikes per plant, 1000-grain weight, and harvest index. The heritability estimates ranged from 59% for grain yield to 99% for days to anthesis. Expected genetic advance (as % of the mean) was ≈34% for number of spikes per plant, number of grains per spike, and 1000-grain weight. Days to heading and to anthesis correlated positively with number of spikes per plant, shoot biomass, and straw biomass but negatively with number of grains per spike and harvest index. The strong direct effect of number of spikes per plant on grain yield was completely counterbalanced by its indirect negative effects via number of grains per spike and 1000-grain weight. Number of grains per spike and 1000-grain weight were positively correlated with grain yield, and they had large direct effects. These two characters, however, were negatively correlated and exhibited a substantial counterbalance effect via one another and via number of spikes per plant. The landraces could be improved by intercrossing the promising genotypes identified in this study, with simultaneous selection for earliness, fewer number of spikes per plant, greater number of grains per spike and heavier grains. For further improvement, crossing programs between the landraces and introduced germplasm may be necessary. This revised version was published online in July 2006 with corrections to the Cover Date.     

Differences in grain/straw ratio,protein content and yield in landraces and modern varieties of different wheat species under organic farming

Hulled wheat species (einkorn, emmer, spelt) are presumed to be an alternative to bread wheat in organic agriculture since the yield penalty is less pronounced under organic farming and generally higher prices can be achieved for specialty grains. The present study analyzed differences between wheat species with respect to biomass production, harvest index, grain yield and protein content. Spring hulled wheat genetic resources and bread wheat check cultivars were grown in organic field trials in the Czech Republic and Austria between 2010 and 2012. Generally, hulled wheat species were inferior in grain yield and distribution of assimilates to the grain compared to modern bread wheat. Biomass production of some emmer and spelt landraces was similar to bread wheat. A higher protein content (+3–6 %) was observed for spelt, however, considering protein yield the differences between spelt and bread wheat became less pronounced. With respect to the recent high market demand for spelt and the absence of available spring grown varieties some of the landraces were identified as valuable resources for the development of spring spelt varieties suitable for organic farming.     

Wheat grain yield and stability assessed through regional trials in the Eastern Gangetic Plains of South Asia

Improving the level and stability of grain yield is the primary objective of wheat breeding programs in the Eastern Gangetic Plains (EGP) of South Asia. A regional wheat trial, the Eastern Gangetic Plains Yield Trial (EGPYT), was initiated by CIMMYT in collaboration with national wheat research programs in Bangladesh, Nepal, and India in 1999–2000 to identify wheat genotypes with high and stable grain yield, disease resistance, and superior agronomic traits for the EGP region. A set of 21 wheat experimental genotypes selected from a regional wheat screening nursery in South Asia, three improved widely grown cultivars (Kanchan, PBW343 and Bhrikuti), and one long-term cultivar (Sonalika) were tested at 9–11 sites in six wheat growing seasons (2000–2005) in the EGP. The 21 experimental genotypes were different in each year, whereas the four check cultivars were common. In each year, one or more of the experimental genotypes showed high and stable grain yield and acceptable maturity, plant height, and disease resistance compared to the check cultivars. Three improved cultivars have already been commercially released in the region through EGPYT and many germplasm lines have been used in the breeding programs as parents. Identification of wheat genotypes with high-grain yield in individual sites and high and stable yield across the EGP region underlines their value for regional wheat breeding programs attempting to improve grain yield and agronomic performance.     

Agronomic Performance of Wheat Doubled-Haploid Lines Derived from Cultivars by Anther Culture

To determine the level of gametoclonal variation among doubled-haploid lines (DHLs) of Triticum aestivum L. developed using anther culture techniques and its effect on agronomic performance, 70 anther culture-derived DHLs of ‘Kitt’ were compared for 7 agronomic traits to 50 single-seed descent-derived lines (SSDLs) of ‘Kitt’ and to the cultivar ‘Kitt’. In a second experiment, 26 DHLs of ‘Chris’ were compared for 7 agronomic traits to 29 SSDLs of ‘Chris’ and to the cultivar ‘Chris’. Each experiment was grown as a randomized complete block design with three replications in three environments. For ‘Kitt’, the DHLs averaged significantly lower grain yields than the comparable SSDLs. For ‘Chris’, the DHLs averaged lower, but not significantly lower, grain yield than the SSDLs. In both ‘Kitt’ and ‘Chris’, the genetic component of variance for yield of the DHLs was significantly larger than that of the SSDLs indicating the presence of gametoclonal variation. The lower average grain yield of the DHLs was explained by a larger group of low-yielding DHLs than was present in the SSDLs. Six ‘Kitt’ DHLs and 3 ‘Chris’ DHLs were lower yielding than the lowest yielding SSDL, respectively. Elite DHLs and SSDLs were similar for mean grain yield performance. Though the DHLs and SSDLs were significantly different for some yield components, the affected yield component changed with the cultivar and there was no consistent effect. Significant genotype × environment interactions were detected for some traits which were caused by changes in the magnitude of differences, rather than reversals in ranking, indicating that low yielding DHLs could be culled on the basis of visual selection or single-environment testing. Hence, gametoclonal variation was induced by the anther culture techniques used in this study, tended to be deleterious for grain yield, and was sensitive to the growing environment. However, as the DHLs and SSDLs had similar expected population means based upon expected gains from selection, this gametoclonal variation should not be a major hindrance to wheat breeding.     

Combining ability and heterosis under pest epidemics in a broad-based global wheat-breeding population

Wheat breeders rarely apply population improvement schemes or select parental sources according to combining ability and heterotic patterns. They rely on pedigree selection methods for breeding new cultivars. This experiment was undertaken to assess the advantages of using diallel crosses to define combining ability and understand heterosis in a broad‐based wheat‐breeding population across different environments affected by yellow rust. Sixty‐four genotypes derived from a full diallel mating scheme were assessed for grain yield in two contrasting growing seasons at two locations for two consecutive years. Parental genotypes showed significant combining ability for grain yield that was affected by yellow rust and genotype‐by‐environment (GE) interactions, both of which affected heterosis for grain yield. Significant GE interactions suggested that decentralized selection for specific environments could maximize the use of this wheat germplasm. Cultivar effects and specific heterosis were the most important factors influencing grain yield. Some crosses capitalized on additive genetic variation for grain yield. This research shows the power of available quantitative breeding tools to help breeders choose parental sources in a population improvement programme.     

Carbon Isotope Discrimination, Leaf Ash Content and Grain Yield in Bread and Durum Wheat Grown under Full-Irrigated Conditions

Integrative physiological criteria, such as carbon isotope discrimination (Δ) and (mineral) ash content (m_a) have been found to be very useful, under drought conditions, to elucidate the association between yield gains and variation of photosynthesis‐related traits and orientate future breeding efforts. Information on this association is scarce under irrigated conditions. The relationships between Δ, m_a and yield were studied in bread wheat (Triticum aestivum L.) and durum wheat (Triticum turgidum L. var. durum) under optimal (drip) irrigation in the arid conditions of north‐west Mexico. Carbon isotope discrimination was analysed on leaves at booting stage and anthesis and on grain at maturity, whereas ash content was measured on the flag leaf at anthesis and maturity. At anthesis, there were differences between bread and durum wheat during grain filling for Δ, but not for m_a. No relationship was found between grain yield and Δ. Leaf ash content at anthesis and maturity showed a broad variability within each species and were associated with grain yield. These results suggest that ash content in leaves could be also used as predictive criteria for yield not only under drought, but also under irrigated conditions, particularly when evaporative demand is high.     

Canopy Temperature Depression Association with Yield of Irrigated Spring Wheat Cultivars in a Hot Climate

This study examines the utility of measurements of canopy temperature depression (TD) below air temperature as an indirect selection criterion for grain yield in breeding of wheat ( Triticum aestivum L.). TD differences can be rapidly assessed using a hand-held infra-red thermometer and may reflect differences in stomatal conductance. Replicated small plot experiments were conducted with 23–24 spring wheat cultivars planted at two dates in the winter cropping cycles of 1991–92 and 1992–93 at a hot low latitude location in Mexico.
Across a two fold range in grain yield at each planting, TD was usually highly significantly correlated with grain yield. Averaging the results for each year, the phenotypic correlation TD vs. yield was 0.84** and 0.89** for 1991–92 and 1992–93, respectively. Correlations were strongest when TD was measured between noon and 4 pm, and were unaffected by crop stage of development (pre-heading, heading, grain fill) or timing relative to irrigation. TD was positively correlated with stomatal conductance. We discuss possible causes of these high correlations, and their implications for wheat breeding.     

Variation at glutenin subunit loci,single kernel characterization and evaluation of grain protein in East African bread wheat varieties

Wheat breeding programs worldwide aim at developing cultivars that meet end user quality attributes demanded by producers, processors, and consumers. Selecting from breeding populations created from well characterized parental germplasm provides the best opportunity of identifying cultivars that combine the best alleles and grain phenotypes for the desired technological applications. In this study, 216 bread wheat lines associated with Ethiopian and Kenyan breeding programs including a few founder lines were profiled for high molecular weight glutenin subunits and low molecular weight glutenin subunits by SDS-PAGE. Additionally, total crude protein, relative puroindoline content by SDS-PAGE, kernel diameter, kernel weight and kernel hardness by SKCS were determined. Extensive allelic variation at the glutenin subunit loci was found, with Glu-B1 and Glu-B3 having highest diversity across subpopulations. Relative to wild type cultivar ‘Alpowa-1-soft’, the founder line BW21 had the lowest puroindoline content. The frequencies of soft and very soft wheat classes were lowest in the Ethiopian subpopulation and highest among the Kenyan lines. Accordingly, 12 lines considered to have optimal combinations of glutenin subunit alleles and kernel characteristics were highlighted and recommended for cultivar improvement.     

Line selection for exploiting durum wheat (T. turgidum L. var. durum) local landraces in modern variety development program

Summary Pure line selection for grain yield applied within four durum wheat local landraces (Triticum turgidum L. var durum) was studied in an effort to determine: (i) the agronomic performance of selected line mixtures (bulks) and their value as potential new cultivars, (ii) the effectiveness of pure line selection for grain yield within local landraces and (iii) the correlated selection response of yield components and kernel quality traits. Four local durum wheat landraces were used. Two of them, Mytilini-1 and Mytilini-2 are still cropped in some rural areas of the island Mytilini whereas the other two, Limnos and Mavragani are maintained in the Greek Gene Bank. Following their preliminary evaluation for agronomic performance under current growing conditions, 100 individual plants from each landrace were randomly selected. Selected plants (pure lines) were field evaluated head to row during 1997–98 and 1998–99 growing seasons. Based on grain yield performance, bidirectional selection, high vs low, was practised within each landrace. Thus the five higher yielding lines and their corresponding lower ones from each landrace were identified. Selected lines, with no further progeny testing, were pooled using a balanced seed composite to form the high yielding five line bulk and its respective low counterpart. The resulting 16 bulks (eight high and eight low) along with their four source landraces and two commercial varieties, Mexicalli and Simmeto, used as checks, entered field testing for agronomic performance in two and one location during 1999–00 and 2000–01 growing seasons respectively. Data for grain yield and yield components (1000 kernel weight, number of kernels, and productive tillers) along with kernel quality data (protein content and vitreous) were recorded. Data for grain yield indicated that the landraces studied seemed to be line mixtures, as expected, since they responded to bidirectional phenotypic pure line selection. The high yielding bulks were of interesting agronomic performance, equivalent to or significantly better than that of the commercial checks and are worth further testing as potential cultivars. Selected high bulks of Mytilini 2 landrace significantly outyielded both the source landrace and the commercial checks maintaining the high protein content of the source landrace, which was significantly higher than checks. This performance provides evidence that the within landraces selection of lines combining high grain yield with high protein content seems to be feasible. In conclusion, evidence is presented that genetic variability seems to be available within the landraces studied which could be worth using in breeding programs. Furthermore the simple pure line selection breeding effort undertaken seemed to be effective in developing line bulks with promising performance and worth further testing as potential cultivars.     

粒叶比在小麦育种上的应用

为提高育种预见性和选择效率,对小麦粒叶比的概念、遗传特性、与产量因素及产量的关系等问题进行了探讨。认为粒叶比不仅是衡量小麦群体库源流协调和单位叶面积光合生产力的指标,而且与群体产量呈极显著的正相关,能在高水平上实现产量因素的协调增长。粒叶比遗传力高,测定方法简单,是一个较好的有实用价值的选择指标。