Zum Einfluß von Saatzeiten, Saatstärken und Sorten auf agronomische Merkmale von Winterweizen in einem System mit geringer Betriebsmittelzufuhr von außen

The influence of sowing date, seed rate, and variety on agricultural characteristics of winter wheat in a low external input system
Growth conditions of winter wheat in agricultural low external input systems, e.g. ecological agriculture, are very different compared to conventional agriculture (mineral nutrition, impact of diseases, competition of weeds). In 1986, 1987, and 1988 the influence of sowing date and seed rate on crop development and grain production was studied with two varieties of winter wheat in field experiments in Northern Hessia.
Drilling after the first decade of October decreases grain yield of both varieties significantly. The decrease was due to poor emergence, low plant densities, and low grain weights. Tillering could not compensate low plant densities, presumably because of low mineralization of nutrients in cold soils during respective growth stages.
Variation of seed rate (350, 500, and 650 viable seeds/m²) had little influence on grain yield. Low plant densities and low numbers of ears per nr after sowing in the end of October could not be improved satisfactorily by increased seed rates.
The ability of varieties of winter wheat to compensate unfavourable growth conditions due to "late" sowing varies considerably. Cultivars which are able to develop a high plant density seem to be more suitable for delayed sowing dates, as compared to varieties which own a high grain weight.
Further investigations concerning wheat production are needed to optimize agricultural low external input systems. Especially sandy soils with quick response to increased ambient temperature, and sites with favourable growth conditions in late autumn and early spring should be considered.     

Extent of RFLP variability in tetraploid populations of alfalfa, Medicago sativa

Seven widely-cultivated alfalfa varieties and three ecotypes adapted to Central Italy were used to evaluate the extent of polymorphism in that species. Twenty plants per accession were analysed with 16 RFLP probes combined with three restriction enzymes (48 probe/enzyme combination in total) and the data were used to compute the Nei's similarity index taken as a measure of inter- and intra-population RFLP variability. The varieties were, in general, more homogeneous than the ecotypes and the cultivars ‘Adriana’ and ‘Florida’ could be differentiated more easily than the others. Few accession-specific hybridizing fragments were scored and seven populations could be distinguished from the others on the basis of significant differences in the frequencies of specific fragments. The DNA of plant populations of several sizes was bulked and the ability to detect a given fragment in pooled samples was related to the fraction of plants having that fragment among the plants forming the bulk. The results are discussed with special emphasis on the practical utilization of RFLPs for varietal identification.     

Annual Medicago as a Smother Crop in Soybean

Use of conservation tillage and narrow row spacing in soybean [Glycine max (L.) Merr.] production has led to increased use of herbicides for weed control. Some producers are seeking alternative weed control methods, such as smother crops, that would reduce dependence on chemical weed control. A successful smother crop must compete strongly with weeds but minimally with the crop. In four environments, we intercropped three annual Medicago spp. (medics) with soybean to test their utility as a smother crop for weed control. Annual medics were intercropped with soybean at rates of 0, 85, 258, or 775 seeds m^?2, and the intercrops were grown with and without weed control. Increasing medic seeding rate decreased weed yields but also reduced soybean herbage and grain yields. For the weed‐controlled treatment, average soybean grain yields declined 7 kg ha^?1 for every 10 seeds m^?2 increase in medic seeding rate. Soybean grain yield was lower when grown with Medicago scutellata L. cv. Sava than when grown with Medicago polymorpha L. cv. Santiago or Medicago lupilina L. cv. George. Soybean grain yield was negatively related (r=?81) to medic herbage production. In the autumn following soybean harvest, medic residue ranged from 200 to 3700 kg ha^?1 depending on the location and seeding rate. Medics provided residue for soil protection, suppressed weeds, but also reduced soybean yields.     

云南籽粒苋种质资源的表型多样性分析

为了系统分析云南籽粒苋种质资源的表型遗传多样性。采用遗传多样性指数、主成分分析、相关分析和聚类分析对104份云南籽粒苋种质资源的30个表型性状进行研究。结果表明,遗传多样性指数最高的质量性状和数量性状分别是主花序形状(1.68)和主花序长度(2.07)。前10个主成分累计贡献率达到73.944%,单株鲜体重与第3、第6、第9主成分极显著正相关,单株粒重与第9主成分极显著正相关。聚类分析将104份种质划分为5类,第Ⅰ类群可为间套种亲本材料,第Ⅱ和Ⅲ类群可为大粒亲本材料,第Ⅳ类群可为优质饲用亲本材料,第Ⅴ类群可为观赏类亲本材料。云南籽粒苋种质资源表型性状具有丰富的遗传多样性,有较大的开发利用潜力。     

Relationship Between Productivity and Phosphate Requirement as a Parameter of Selection in Medicago rigidula (L.) Allioni

Among one hundred lines of Medicago rigidula (L.) Allioni, fifteen (5 high-producing, HP, 5 intermediate-producing, IP, and 5 low-producing, LP) were chosen as experimental material because of their different dry-matter production when grown at 0.5 mg L^-1 of P₂O₅ in hydroponic solution (critical level). The aim of this work was to evaluate the response to selection with respect to dry-matter yield (DMY), made at 0.5 mg L^-1 of P₂O₅ and to check if superior lines could also be isolated when plants were grown at 20 and 200 mg L^-1 of P₂O₅. Results show that HP lines were also superior with respect to DMY (g/plant) at the higher phosphorus concentrations. Highly-productive line selection in M. rigidula can also be achieved when plants are grown at a critical level of phosphorus in the nutrient solution. Phosphate content in the dry matter produced and phosphatase activity were also analysed. Plants of the more-productive lines were characterized by lower phosphate content per unit dry matter and by a higher phosphatase activity.     

Penetrance of creeping-rootedness in clonal progenies of lucerne and observations on underground morphology of plants differing for this character

Elaeis oleifera or ‘caiaué’, a close relative of oil palm (E. guineensis), has some agronomic traits of great interest for the oil palm genetic breeding such as slow growth, oil quality (mostly unsaturated) and disease resistance. An analysis of a Brazilian oil palm germplasm collection was carried out using RAPD (Random Amplified Polymorphic DNA) markers with the objective of understanding the genetic variation of ‘caiaué’ accessions collected in the Amazon Forest in the last two decades. A sample of 175 accessions obtained along the Amazon River Basin was analyzed and compared to 17 accessions of oil palm from Africa. Ninety-six RAPD markers were used in the analysis, of which fourteen were shown to be specific to oil palm, while twelve were specific to ‘caiaué’. Results showed that the Brazilian ‘caiaué’ accessions studied have moderate levels of genetic diversity as compared to oil palm accessions. The data allowed the establishment of similarity groups for ‘caiaué’ accessions, which is useful for selecting parental plants for population breeding. Cluster analysis showed that, in general, genetic similarities are not correlated to geographical distances, but consistent with geographical dispersal along the Amazon River network. AMOVA showed that most of the genetic variation is found within populations, as expected for anallogamous and long-lived perennial species. The study provides important information to define strategies for future collection expeditions, for germplasm conservation and for the use of E. oleifera in breeding programs. This revised version was published online in August 2006 with corrections to the Cover Date.     

The taxonomic characterisation of annual Beta germplasm in a genetic resources collection using RAPD markers

Summary Annual beets in the genus Beta section Beta represent an important genetic resource. Representative accessions of annual beets from a beet germplasm collection were analysed using RAPD to assess the patterns of variation and relationships among them. Using arbitrary primers, markers showing variation across accessions were identified. A dendrogram of similarity was produced using these molecular markers. All the accessions analysed were classified into three major groups corresponding to species or subspecies macrocarpa, adanensis and maritima. Macrocarpa was shown to be the most divergent group in this section. Using RAPD molecular markers, it was possible to ascribe an accession to one of three taxonomic groups and overcome much of the confusion encountered when morphological traits are used for identification. The group of maritima was found to be more polymorphic than either the group of macrocarpa or adanensis at both accession and subspecies levels.     

梨属植物等位酶遗传多样性研究

利用超薄平板微型聚丙烯酰胺凝胶的等电聚焦电泳技术,对286份梨材料进行了等位酶遗传变异分析。在8个酶系中共检测到19个清晰位点和82个等位基因,19个位点均为多态位点,位点最大等位基因数为6,体现出梨丰富的遗传种质多样性;不同的居群具有特有等位基因;通过82个等位基因可以将286份材料完全区分开,表明等位酶基因型指纹可用作梨品种区分与鉴定的依据。     

The effectiveness of evaluating wild species: searching for sources of resistance to bruchid beetles in the genus Vigna subgenus Ceratotropis

A species level germplasm collection representing 76% of known taxa in the genus Vigna subgenus Ceratotropis was evaluated for resistance to two species of bruchid beetles, Callosobruchus chinensis and C. maculatus. Seven taxa consisting of 29 accessions were found to be resistant to C. chinensis and 4 taxa consisting of 24 accessions were found to be resistant to C. maculatus. This compared with no resistant accessions being found in several hundred landrace accessions of mungbean, V. radiata var. radiata, in the same subgenus. Sometimes resistance was found in all accessions of a particular taxon, such as complete resistance to both C. chinensis and C. macualtus in V. umbellata. Other taxa showed intra taxon variation for resistance such as V. reflexo-pilosa andV. minima. The levels and patterns of resistance among taxa were diverse. The results suggest that various factors cause resistance to bruchid in the subgenus Ceratotropis. While the number of eggs laid on seeds generally reflected seed size, one small seeded cultivar of V. mungo var. mungo, black gram, had an unusually high number of eggs laid per seed. No correlation was found between seed size and levels of resistance. The species level germplasm collection, which reflects the core collection concept in trying to maximize genetic diversity in a limited number of accessions, has enabled a large number of potentially useful sources of resistance to bruchid beetles to be found efficiently. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

诱变在作物遗传育种中的应用

诱变育种是通过人工诱变方法对作物基因组进行改造。诱变既能使作物基因组DNA发生缺失、插入、置换或异位等,也可以对基因进行定点突变或定向敲除、打破基因间的连锁平衡,从而产生新的性状。为了探讨不同诱变技术的方法、优缺点以及在作物遗传育种中的运用,本文归纳了物理、化学、生物和空间等技术诱发突变的原理及方法;比较了传统育种和诱变育种的优缺点;分析了不同诱变技术的作用机理;总结了不同诱变技术在不同作物上的运用。本文指出了目前诱变育种的缺陷,展望了诱变育种的前景,为探索诱变育种在现代化育种中的作用提供了理论和技术支持。     

Chloroplast microsatellite variations in tetraploid alfalfa

Four chloroplast simple sequence repeat (cpSSR) loci were identified in alfalfa (lucerne), Medicago sativa L. The occurrence of allelic variation at these loci was evaluated in 100 plants from 10 populations of tetra‐ploid alfalfa, belonging to four Italian ecotypes and to an Italian (‘Lodi’) and an Egyptian (‘Iside’) variety. Twenty‐four different alleles were identified, four of which were exclusive to the ‘Iside’ variety. The genetic relationship among plants and among populations was analysed by computing an analysis of molecular variance and an unweighted pair group means analysis clustering. This analysis allowed clear separation of the ‘Iside’ variety from Italian germplasm and the recognition of close relationships within the Italian populations. The data presented suggest that cpSSR analysis of tetraploid alfalfa could be used for germplasm polymorphism analysis.     

Regional patterns of microsatellite diversity in Ethiopian tetraploid wheat accessions

This study was conducted to assess regional patterns of diversity of Ethiopian tetraploid wheat accessions and to identify areas of diversity that can be used as source of new germplasm for developing high yielding and stable varieties. A collection of 133 Ethiopian tetraploid wheat accessions and eight introduced cultivars was analysed using 29 wheat microsatellite markers. A total of 383 alleles were detected with an average value of 13.14 alleles per locus. Relatively more alleles were observed in the B genome than in the A genome. Gene diversity indices ranged from 0.08 to 0.95, with a mean value of 0.72. Accessions collected from the same region were pooled and the number of alleles and gene diversity were calculated over the 29 simple sequence repeats for each region. Higher numbers of alleles were detected in the Shewa region (8.72), followed by Tigray (5.86) and Hararghe (5.76). The highest average gene diversity value was found in Shewa (0.65), followed by Gondar (0.64). No significant correlation was observed between geographic distance and genetic distance. Out of 383 different alleles detected, 93 (24.4%) were observed to be region‐specific. Region‐specific alleles were found across all chromosomes except for Xgwm752, Xgwm155 and Xgwm148. Genetic similarity coefficients were estimated for all the possible 55 pairs of regional comparisons and they ranged from 0.16 to 0.52, with a mean value of 0.50. All provinces were differentiated in the UPGMA cluster diagram.     

A definition of the optimal allocation of effort in conservation of plant genetic resources-with application to sample size determination for field collection

Summary A criterion was presented to define the most efficient strategy for the exploration and maintenance of plant genetic resources. All of the three factors composing the efficiency. i.e., multiplicity of target populations. the amount of expenses, and goodness for individual populations of the conservation manipulation adopted, were incorporated in the present criterion. Sample size per target population for field collection was investigated on the basis of this criterion, leading to the conclusion that the number of visited populations rather than sample size per population determines the overall efficiency of a collection project as a whole. Without any particular reason, intensive sampling for a limited number of populations is not logical. A sample size as small as ten plants per site or population was estimated reasonable to cover a large target area.     

Intersubgeneric Crossability in the Genus Glycine Willd.

In intersubgeneric crosses between wild perennial Glycine species of submenus Glycine and soybeans, Glycine max (L.) Merr., of subgenus Soja, all the putative hybrid pods aborted from 9 to 30 days after pollination (DAP). Spraying of 70 ppm gibberellic acid on hybridized gynoecia facilitated pod retention. Fluorescence microscopy revealed normal pollen germination and pollen tube growth in all the intersubgeneric crosses except in the G. cyrtoloba × G. max cross.     

Variation in Illinois bundleflower (Desmanthus illinoensis (Michaux) MacMillan): A potential perennial grain legume

Illinois bundleflower, Desmanthus illinoensis (Michaux) MacMillan, is an herbaceous perennial legume native to the central and southeastern USA. It has been identified as a potential perennial grain legume. To describe variation among natural populations for agriculturally desirable characteristics, 141 accessions of D. illinoensis and one of D. leptolobus were evaluated in common garden plantings established in 1988 and 1990. Characteristics showing diversity among populations included seed yield, plant height, growth habit, days to maturity, 100 seed weight, and shatter resistance. Eight characteristics were analyzed by principal components and cluster analysis. The resulting four clusters accounted for 56% of the variation among accessions. One cluster was distinctive in having plants with vigorous, prostrate first year growth, poor winter hardiness, and large seed. Three accessions also had indehiscent legumes useful for breeding shatter resistance. There appears to be sufficient variation to support genetic improvement of agricultural characteristics of Illinois bundleflower. This revised version was published online in August 2006 with corrections to the Cover Date.     

Heritability and gain from selection for field resistance against multiple root-knot nematode species (Meloidogyne incognita race 1 and M. javanica) in carrot

Heritability and gain from selection of traits associated with field resistance to multiple root-knot nematode species were estimated in carrot (Daucus carota L.). Experimental plots were uniformly and simultaneously infested with Meloidogyne incognita race 1 and M. javanica. Forty-seven half-sib families derived from the cv. ‘Brasília’ were evaluated for: (1) percentage of commercial roots with non-galling symptoms (%RNG); (2) percentage of commercial roots with gall symptoms (%RGS) and (3) percentage of non-commercial roots (%NCR). The cultivars ‘Brasília’ (resistant), ‘Carandaí’ (intermediate) and ‘Nova Kuroda’ (susceptible) were employed as standards. Broad-sense heritability estimates were 61.9 % for %RNG; 30.6 % for %RGS and 67.9 % for %NCR. However, the gains from selection were very small for all traits. The genotypic correlation between %RGS and %NCR was –0.38 and the correlation between %RNG and %RGS was 0.13. Selection on increasing %RNG resulted in a negative correlated response on %NCR (genotypic correlation = –0.99) indicating repulsion phase linkage(s) between the genetic factor(s) controlling these traits. The phenotypic correlation of –0.88 between %RNG and %NCR suggested that incomplete penetrance and dosage effects might be involved in the expression of these traits. Selection of superior genotypes (i.e. high %RNG, low %RGS, and low %NCR) can be achieved. ‘Brasília’ was among the genotypes selected for the following cycle of recombination reinforcing the notion that this cultivar is one of the most promising sources of stable, wide-spectrum field resistance to Meloidogyne species in D. carota. This revised version was published online in July 2006 with corrections to the Cover Date.     

贵州茶树遗传资源的多样性和创新利用

贵州茶树遗传资源丰富，茶树品种地域特征明显。本文全面介绍了贵州茶树资源创新利用的现状，指出保护茶树遗传资源的多样性，积极开展茶树资源的创新与利用研究，实现贵州茶业可持续发展。     

燕麦种质资源在晋北寒旱生态区的鉴定

为探索国家现代农业燕麦荞麦产业技术体系提供的100份燕麦资源的利用价值,并从中筛选出可直接利用的优质品种,采用田间观察和综合分析的方法,研究其农艺性状的变异情况和部分性状的遗传多样性表现。农艺性状分析表明：轮层数、株高和千粒重的稳定性相对较好,在育种过程中较容易选择;上数第2片叶长、上数第2片叶宽和穗粒重的变异系数较大,在育种中应放宽标准。若干性状的遗传多样性分析表明：皮裸性、粒色、茎叶蜡质的遗传多样性指数偏小;粒形、芒色、茎粗度和旗叶叶相的遗传多样性指数较大。通过鉴定筛选出13个抗旱、抗病、早熟的优质燕麦品种,20个大穗大粒品种,以及一系列单一性状突出的品种。为燕麦新品种选育和合理利用燕麦种质资源提供理论依据。