The potential use of self-incompatibility for breeding F1 hybrids of naturally self-pollinated vegetable crops

Summary The available evidence indicates that F₁ hybrid varieties of most naturally self-fertilized crops have potentially great economic value. The main deterrent to their wider use is the present high cost of seed production. This can be greatly reduced by breeding into these crops systems for controlled cross-fertilization. In those crops whose flowers lack nectaries (e.g. tomatoes and lettuce), self-incompatibility appears to offer a more efficient cross-fertilizing system than male sterility. Self-incompatibility systems are already available in species of tomatoes, lettuce and beans. The prospect of finding self-incompatibility in other species closely related to the remaining self-fertilized crops appears to be good. Besides introducing self-incompatibility into self-fertilized crops, the breeder also needs to introduce an efficient system of pollen transfer between plants.Paper No. 1574 of the Colorado State University Experiment Station     

The use of genetic,manual and chemical methods to control pollination in vegetable hybrid seed production: a review

Production of hybrid varieties of vegetable crops is currently a desired breeding goal, due to their remarkable agronomic performance and to the possibility of intellectual property protection. However, efficient hybrid production requires a careful pollination control to guarantee the hybrid nature of F₁ seed. Several technologies ranging from manual emasculation to genetic transformation are used to inhibit pollen production in mother plants. In this review, we examine the principles underlying strategies like genetically determined systems (genic male sterility, cytoplasmic–genic male sterility, self‐incompatibility) and other methods (manual emasculation, chemical‐hybridizing agents) in different species, considering the benefits and drawbacks of their adoption. Finally, we present the current state of the art for vegetable hybrid seed production.     

Forage quality of genetically diverse alfalfa germplasms at four phenological growth stages

Summary Forage quality of various alfalfa (Medicago sativa L.) cultivars has been determined under different environmental conditions, and numerous trials with alfalfa have documented an inverse relationship between forage quality and maturity. Little information is available, however, regarding the comparative forage quality of the germplasm sources from which most USA cultivars were developed. We compared forage quality of these germplasm sources at four phenological stages under disease- and insect-free conditions in a greenhouse. Germplasm sources (cultivars) tested were: Indian (Sirsa #9), African (African), Peruvian (Hairy Peruvian), Flemish (DuPuits), Turkistan (Lahontan), Chilean (Kansas Common), M. varia (Grimm), and Ladak (Ladak). Four harvests were taken and forage was separated into four phenological stages: vegetative, early bud (1–3 buds-per-stem), late bud (>3 buds-per-stem), and bloom. The germplasm source X phenological stage interaction was significant for crude protein (CP) and in vitro digestible dry matter (IVDDM) concentrations. M. varia showed the least decline in IVDDM and CP with increasing maturity. M. varia had higher IVDDM than did African and Indian at late bud and bloom stages. Indian and Flemish had higher CP than did Turkistan and Peruvian at late bud and bloom stages. Alfalfa germplasm sources differ in forage quality when comparisions are made within similar stages of phenological development.Joint contribution of the Dept. of Agronomy and USDA-ARS, Kansas Agricultural Experiment Station, Manhattan, KS 66506, USA. Contribution no. 90-475-J.     

苜蓿-玉米-小黑麦“草粮兼顾”型种植模式产量及经济效益分析

针对苜蓿生产中存在的问题,为了提高农业产能和经济收益,本研究提出并初步阐述了苜蓿-玉米-小黑麦"草粮兼顾"型种植模式,通过裂区试验设计,以苜蓿种植行数为主处理,以玉米/小黑麦种植行数为副处理,探讨3种作物不同的种植搭配方式对产量和经济收益的影响,并试图通过产量分析简单阐明不同作物的竞争关系。结果表明:苜蓿5行,玉米2行,小黑麦4行的种植模式下3种作物的时空搭配最为合理,利于作物间互相促进,尽量减少种间竞争带来的损失,产量和经济收益最佳。     

Light competition for invasive species control: A model of cover crop–weed competition and implications for Phalaris arundinacea control in sedge meadow wetlands

Summary Since resource competition plays a critical role in many plant invasions, controlling invasive vegetation may require managing the supply of limiting resources. For example, lowering light availability with a cover crop might prevent invasions during community establishment in light-limited restored ecosystems. However, most cover crops evaluated for invasive species control either do not adequately suppress invasives or equally suppress desired species. To improve our ability to predict cover crop effectiveness, we use a theoretical model of plant competition to identify potential mechanisms by which cover crops might favor desired species over invasives. In addition, we consider the model's implications for controlling an invasive forage, Phalaris arundinacea, in restored sedge meadows. The model suggests that cover crops will improve the outcome of competition between desired and invasive species only when (1) desired species have lower minimum light requirements than invasive species and (2) invasive species dominance results from rapid establishment and resource preemption. Cover crops in the model favor desired species over faster-growing invasives because faster-growing invasives are positioned higher in the canopy. Invasive species higher in the canopy shade desired species more than desired species shade invasives. Consequently, by reducing invasive species biomass, cover crops give desired species a competitive advantage. The simple requirements for cover crop success in the model suggest that cover crops may be effective for invasive species control in light-limited restored ecosystems. The available information on P. arundinacea responses to shade suggests, however, that cover crops are unlikely to favor sedge meadow species over P. arundinacea.     

Participatory varietal selection in rice in Nepal in favourable agricultural environments – A comparison of two methods assessed by varietal adoption

Two participatory approaches to varietal selection were compared in February-sown (Chaite) rice and main-season rice in high potential production systems in Nepal. One method, called farmer managed participatory research (FAMPAR), was researcher intensive, while the other, called informal research and development (IRD), demanded fewer resources. The trials were conducted in 18 villages in high potential production systems in Chitwan and Nawalparasi districts of Nepal. Six new varieties of Chaite rice and 16 of main-season rice were tested in over 300 trials of Chaite rice and nearly 1100 trials of main-season rice over two years in 1997 and 1998. Surveys were done in 1997, 1998 and 1999 to record the extent of adoption and spread of the new rice varieties in the study villages. In many cases, farmers tested varieties for two years before deciding whether to adopt or drop them. Varieties were quite widely accepted, adopted for niches in a few villages, or rejected. The two participatory approaches identified the same varieties, but FAMPAR, which used formal survey methods, was more useful for diagnosing reasons for adoption or rejection. However, IRD used much cheaper anecdotal methods of evaluation, so it was more cost-effective. Moreover,farmer-to-farmer seed dissemination was higher in IRD villages, probably because farmers in FAMPAR villages felt that the project would re-supply seed if needed. The benefits from both approaches are considerable, but to adopt them substantial policy changes in varietal testing, release and extension systems will be required. This revised version was published online in August 2006 with corrections to the Cover Date.     

苜蓿种子产量及其构成因素的多样性研究

在2005-2006年连续两年在条播条件下对国内外62份苜蓿种质55个4龄苜蓿品种的种子产量及其构成因素的多样性和相关性进行了研究.结果表明所有参试的苜蓿品种间的种子产量差异比较大,生殖枝数/m2、每生殖枝花序数、每花序小花数、每花序小荚数,每小荚种子数品种间存在较大的变异,遗传多样性比较复杂.通过对两年的数据进行相关分析发现,种子产量与牛殖枝花序数在两年中相关均极显著,可以作为高种子产量品种选育的重要指标之一.实际种子产量占潜在种子产量百分比在品种之间和茬次之间均存在较大差异,而且发现两年中实际种子产量占潜在种子产量几乎均小于4%,绝大部分在1%～2%之间.研究发现千粒重与其它指标相关性不显著,国内品种千粒重表现比较大的变异,多数品种间千粒重差异较大,但国外品种间(除Jindera外)千粒重变异较小,品种间差异不显著(p>0.05).     

基于光致发光光谱的水稻品种快速鉴别研究

水稻是中国最重要的粮食作物之一,其种子品种鉴别是目前农业生产、作物育种和种子检验的重要问题。由于品种鉴别比较困难,每年因品种搞错和纯度差而造成的经济损失巨大。为此提出了一种应用光致发光光谱分析技术与化学计量学相结合的快速、无损鉴别稻谷品种的新方法。为了实现水稻品种的快速无损鉴别,采用北京卓立汉光仪器有限公司生产的光致发光光谱分析仪,对从长江大学农学院收集的5个不同品种的水稻共125个样本进行650~1000 nm波段光致发光光谱采集,获取了每个品种水稻各25个样本数据。将光谱数据经主成分分析压缩成数目较少的新变量（主成分）,其中前7个主成分能够解释99.696%的原始光谱信息。因此将前7个主成分作为BP神经网络的输入,不同水稻的品种值作为BP神经网络的输出,建立水稻品种的模式识别模型。样本被随机的分成包含100个样本的建模集和25个样本的预测集。结果表明,5次随机抽样建模的预测正确率均达到100%。同时也表明,主成分分析的数据压缩能力好,通过主成分分析和BP神经网络相结合建立模型进行不同品种水稻鉴别具有分析速度快、鉴别能力强的特点,为快速鉴别水稻品种提供了新的方法。     

Dry matter and qualitative characteristics of alfalfa as affected by harvest times and soil water content

The best trade-off between quantity and quality in forage crops is one the most important targets of the agronomic research, since quantitative and qualitative traits are generally inversely correlated. With the aim of exploring the effect of harvest time (early and late), soil water content (irrigated and rainfed) and variety (Equipe, Europe and Midi) on duration, yield and quality of alfalfa, a four year trial was carried out in a Mediterranean environment. Early cut resulted in a reduction of forage yield (12%) with a faster reduction of longevity, but with a higher quality characteristics in terms of protein (20.2%) and fibre (23.1%) compared to the late cut (18.0 and 25.9%, respectively for protein and fibre). Dry treatment led to a limited reduction of yield and quality traits, suggesting alfalfa is a potential forage resource for the improvement of hilly areas of Mediterranean environment. The tested varieties show all a good regrowth capability allowing three, sometimes four, cut per year. The obtained results pointed out that the combination of early and late harvest times would allow a better distribution of the forage production between the months of June and September as well as a fair useful forage regrowth during the months of October and November.     

Estimates of variance components and repeatability for total forage yield in rye: implications for breeding

Cereal rye (Secale cereale L.) is an important forage crop in the USA for stocker cattle (Bos sp.) production, thus making forage yield an important breeding objective for the crop. However, little information is known about the repeatability for forage yield in this crop. The objectives of this research were to: (i) estimate variance components for forage yield from long‐term variety trials, (ii) estimate the repeatability for forage yield and (iii) relate this to breeding strategies for increased forage yield in rye. Trials were conducted over 14 years where 97 USA open‐pollinated varieties (OPVs) were evaluated. Repeatability ranged from 0.57 to 0.86 when the data were analysed by year for the 3 years with significant genotype main effects. Possible explanations for the lack of significant genotype main effects are discussed. Practical implications of these findings indicate that the development of improved cultivars with greater forage yield will require improved methods of selection based on family performance rather than the current methods based primarily on single plant visual selection.     

Modified synthetic varieties: a breeding method for forage crops to exploit specific combining ability

Hybrid varieties have not become commercially successful in perennial and self‐incompatible forage crops because of their severe inbreeding depression and/or ineffectiveness in commercial seed production. Here, a modified synthetic variety (MSV), a breeding method for forage crops is proposed, where specific combining ability (SCA) is exploited in a way different from that in hybrids. As Syn‐l seeds from only two of its parental clones are used to produce its Syn‐2, its performance in Syn‐2 partially depends on the SCA between the two seed parents. The inbreeding coefficient of MSVs can be as low as that of conventional synthetic varieties sold today. To evaluate its advantages, 15 modified synthetic strains (MSSs) of timothy were developed from a set of Syn‐l seeds of a conventional synthetic strain (CSS) having six parental clones. An MSS (Syn‐2) showed a yield level equivalent to and a disease score significantly lower than the CSS (Syn‐1) in a field test. The diallel crossing analysis implied that the SCA effects are influential for yield, and that MSV or other SCA‐exploiting breeding methods have the potential to improve the yield level of timothy effectively.     

Effect of Overseeding Forages into Alfalfa on Alfalfa Weevil, Forage Yield and Quality

Many alfalfa ( Medicago sativa L.) fields are sprayed each year with insecticides to control Egyptian alfalfa weevil ( Hypera brunneipennis ) and the alfalfa weevil ( Hypera postica ). Overseeding various species of legumes and grasses into established alfalfa has been proposed as a method to mitigate weevil damage without insecticides. Established fields of alfalfa were overseeded with legumes and grasses in randomized complete block designs in three years of study in a Mediterranean climate in the Sacramento Valley of California, USA. Several overseeding practices maintained or increased yields compared with the insecticide-sprayed treatment. Overseeding increased or maintained forage yield, eliminating the need for insecticides. However, overseeding did not prevent weevil damage to alfalfa. Overseeding is best used to extend the life of alfalfa stands in the final year of production, since overseeding can thin alfalfa stands. Market acceptance for mixed-species hay and harvest management of overseeded forages are the most important limitations to overseeding practices.     

中国牧草产品国际贸易格局研究及启示

为研究中国牧草产品的贸易量、贸易结构、贸易伙伴的历史趋势和变化规律,采用描述性统计以及定量计算函数关系的方法分析1996—2014年间中国牧草产品国际贸易格局。结果发现：2008年以来,中国苜蓿干草和燕麦草的进口量都呈现指数式增长趋势,进口量与中国大型奶牛场的奶牛存栏头数呈现显著正相关关系。中国牧草产品主要进口国是美国和澳大利亚。为了保障粗饲料供给安全,中国应该采取的措施是充分利用国内、国际2个市场和2种资源,有效补充对国内优质饲料的供给。燕麦草正值发展的有利时机,应该借鉴澳大利亚燕麦草产业发展经验,重视发展燕麦草产业。同时应该调动国内各种资源发展牧草产业,从而保障中国优质安全的乳制品与牛羊肉产品的供应。     

Evolution in crop–livestock integration systems that improve farm productivity and environmental performance in Australia

Australian farming systems have an enduring history of crop–livestock integration which emerged in the face of high climate variability, infertile soils and variable landscapes. Ley farming systems with phases of shorter annual legume pasture phases with cereal crops predominate but, emerging sustainability issues and the need to manage risk is driving ongoing innovation in crop–livestock integration. We discuss the recent evolution of selected innovations that integrate crop and livestock production and their impacts on farm productivity, sustainability and business risk. Dual-purpose use of cereals and canola (Brassica napus) for forage during the vegetative stage while still harvesting for grain is now practiced throughout southern Australia's cropping zone. This practice provides risk management benefits, diversifies crop rotations, reduces pressure on other feed resources and can significantly increase both livestock and crop productivity from farms by 25–75% with little increase in inputs. Sacrificially grazing crops when expected grain yield is low and/or livestock prices are attractive relative to grain provides further flexibility in crop–livestock management systems vital for business risk management in a variable climate. Replacing annual pastures with perennial pasture phases in rotation with crops can provide a range of benefits including improved hydrological balance to reduce dryland salinity, subsoil acidification and water-logging, provide a management tool for herbicide-resistant or problem weeds, improved soil nutrient and carbon stocks as well as increased livestock productivity by filling feed gaps. In some environments, integration of perennial forages in mixtures with cropping, such as alley cropping and inter-cropping, also provide options for improving environmental outcomes. These practices are all innovations that provide flexibility and enable tactical decisions about the mix of enterprises and allocation of land and forage resources to be adjusted in response to climate and price. We discuss these innovations in the context of the emerging constraints to crop–livestock integration in Australia including the continuing decline in labour availability on farms and increasing management skill required to optimise enterprise profitability.     

Effects of Soil Moisture Deficit on Forage Quality, Digestibility, and Protein Fractionation of Kura Clover

Kura clover (Trifolium ambiguum M.B.) is a persistent rhizomatous forage legume with great potential for permanent pastures. The effects of a soil moisture deficit on forage quality, digestibility and protein fractionation of two cultivars of Kura clover (Endura and Rhizo) were investigated in this study for 1 year. The responses of alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.) were also characterized. Stands of each species were field‐grown and submitted to two soil water regimes promoting soil moisture deficits and well‐watered (i.e. control) conditions. There were no interactions between species and soil water regimes. Soil moisture deficit increased acid detergent fibre (ADF) but reduced acid detergent lignin (ADL) content and consequently increased forage digestibility. It had only minor effects on protein content and fractionation. Species varied for most parameters measured. Kura clover generally had the lowest neutral detergent fibre (NDF), ADF and ADL contents, and consequently the greatest digestibility (83.9 %). Species also differed in their crude protein fractionation. Kura clover and red clover had a lower proportion of non‐protein nitrogen (NPN; A fraction) and a greater proportion of true protein (B fraction) (30.9 and 64.5 %, respectively) than alfalfa (36.4 and 57.4 %, respectively). Kura clover also had the lowest proportion (i.e. 4.7 %) of acid detergent insoluble protein (ADIP; C fraction) of all species tested. Endura Kura clover often had a higher forage quality than Rhizo. This study confirms that Kura clover produces high‐quality forage and provides the first estimates of protein fractionation in this species.     

AFLP fingerprinting in Medicago spp.: Its development and application in linkage mapping

Cultivated alfalfa (Medicago sativa L., 2n= 4x= 32) is one of the most important forage crops in temperate climates. The genus Medicago includes diploid species that are a valuable source of wild germplasm for studying the reproductive system of alfalfa and its abnormalities. A linkage map of an apomeiotic mutant of Medicago falcata (L.) Arcang. (2n= 2x= 16) that spanned 368.6 cM and included 29 amplified fragment length polymorphism (AFLP), 35 random amplified polymorphic DNA (RAPD) and three restriction fragment length polymorphism (RFLP) loci was constructed using a one-way pseudo-testcross mapping strategy. The success of such a strategy depends on the presence of sufficiently high levels of heterozygosity in the individual plant which is being mapped and on the informativeness of the marker system that is used. In general: (1) highly informative and reproducible RAPD and AFLP fingerprints were generated and several genome-specific primers selected; (2) of 67 marker loci mapped, 51 were arranged in 11 main linkage groups and eight additional couples of linked marker loci were detected; (3) mapping of an F₁ population theoretically allowed a better estimation of linkage distances since it avoided segregation distortion (x² analyses revealed segregation distortion in only 5.2% of marker loci); (4) the high frequency of unlinked marker loci obtained suggests that, in this alfalfa genotype, DNA markers are distributed throughout the genome. This type of genetic map should find application and prove useful in marker-assisted selection and map-based breeding programmes in meiotic mutants of alfalfa for which there is a lack of suitable genetic markers.     

Variation of DNA methylation and phenotypic traits following unilateral sexual polyploidization in <Emphasis Type="Italic">Medicago</Emphasis>

Sexual hybridization is an important generator of biodiversity and a powerful breeding tool. Hybridization can also overcome ploidy barriers when it involves 2n gametes, as in the case of unilateral sexual polyploidization (USP) that has been utilized in several crops, among which alfalfa. This research was aimed at gaining insights into the effects of USP on genome methylation and on phenotypic traits in alfalfa, an important forage species. The Methylation-Sensitive Amplified Polymorphism technique was used to estimate the cytosine methylation changes occurring in a tetraploid (2n = 4x = 32) USP progeny from crosses between a diploid Medicago sativa subsp. falcata genotype that produces 2n eggs and a cultivated tetraploid Medicago sativa subsp. sativa variety. De novo methylation or demethylation in the USP progeny were observed for 13% of the detected genomic sites, indicating that methylation changes can be relevant. USP plants showed larger surface area of the leaf epidermis cells than both parents, but this did not result in larger leaf size or higher plant biomass. They displayed significant higher ovule sterility than the tetraploid parent, but normal fertility was observed in crosses with unrelated male testers. We conclude that hybridization and sexual polyploidization resulted in novel variation in terms of remodeling of the methylation landscape as well as changes in phenotypic traits in alfalfa.     

盐胁迫对苜蓿种子发芽性状的影响及其耐盐性评价

为了阐明盐胁迫条件下紫花苜蓿种子的发芽性状表现和种子萌发期耐盐性能强弱,同时为改良盐碱化土壤提供更加耐盐碱的植物品种,提高盐碱化土地资源利用率,本试验以5个苜蓿(Medicago sativa)品种为材料,采用不同浓度NaCl处理(0、0.4%、0.8%、1.2%),研究了不同盐浓度对苜蓿种子发芽率、发芽势、苗高、根长的影响。结果表明,盐胁迫对苜蓿种子发芽性状均有较大影响,随着NaCl浓度的提高,苜蓿种子发芽率和发芽势降低,苗长和根长明显缩短,而且,高质量浓度盐胁迫对苜蓿种子发芽性状的影响尤为显著。不同苜蓿品种在不同盐浓度间的差异显著;品种间各指标的表现不尽相同,发芽势与发芽率指标在品种间的差异显著,苗高和幼根长指标在品种间的差异不显著。综合单项指标耐盐系数和品种综合耐盐指数来看,5个苜蓿品种的耐盐性能强弱顺序为‘Magnum salt’>‘中苜1号’>‘维多利亚’>‘巨人201T’>‘皇冠’。     

Village seed systems and the biological diversity of millet crops in marginal environments of India

The study relates village seed systems to biological diversity of millet crops grown by farmers in the semi-arid lands of Andhra Pradesh and Karnataka, India. In these subsistence-oriented, semi-arid production systems the environment is marginal for crop growth and often there is no substitute for millet crops. Across communities, farmers grow 13 different combinations of pearl millet, sorghum, finger millet, little millet, and foxtail millet varieties, but individual farmers grow an average of only 2–3 millet varieties per season. The “village seed system” in this study refers to all channels through which farmers acquire genetic materials, separate from or in interaction with the commercial seed industry, observed at the local level. Data are compiled through household surveys and interviews with traders and dealers in village and district markets. Based on the concept of the seed lot, several seed system parameters are defined and measured by millet crop. Most seed transactions, including gifts of seed, appear to be monetized. Seed supply channels differ by improvement status of the genetic material. Regression results confirm that seed system parameters are statistically significant determinants of the spatial diversity of millet crops measured at the village level. Furthermore, both the trade through weekly village markets (shandies) and through the formal seed supply channel contribute positively to the breadth of genetic materials in these communities. Ways should be found to strengthen and improve the overall efficiency of the seed system, including both formal and informal channels, in order to reduce the costs to farmers of procuring and managing diverse crop varieties.     

A decade of Tropical Legumes projects: Development and adoption of improved varieties,creation of market‐demand to benefit smallholder farmers and empowerment of national programmes in sub‐Saharan Africa and South Asia

This article highlights 12 years (2007–2019) of research, achievements, lessons learned, challenges and gaps in discovery‐to‐delivery research in legumes emanating from three projects, collectively called Tropical Legumes (TL) with a total investment of about US$ 67 million funded by the Bill & Melinda Gates Foundation. These projects were implemented by three CGIAR centres (ICRISAT, CIAT and IITA) together with 15 national agricultural research system partners in sub‐Saharan Africa and South Asia. The TL projects together with some of their precursors and complementary projects from other agencies, facilitated the development of 266 improved legume varieties and the production of about 497,901 tons of certified seeds of the target legume crops in the focus countries. The certified seeds have been planted on about 5.0 million ha by more than 25 million smallholder farmers in the 15 countries and beyond, producing about 6.1 million tons of grain worth US$ 3.2 billion. Furthermore, the projects also trained 52 next generation scientists that included 10 women, by supporting 34 Masters degrees and 18 PhD degrees.