Drought stress in sunflower causes inhibition of seed filling due to reduced cell-extension growth

Cultivation of sunflower (Helianthus annuus L.) as one of the most important oil crops is of great importance, especially with focus on drought tolerance under the current climate change. Less precipitation and increasing temperatures lead to more regions with drought problems. In a container experiment, with two different sunflower cultivars, drought stress of 40% water-holding capacity was applied at the seed-filling phase and compared to a control group with regular irrigation to 70% water-holding capacity. Four intermediate harvests during the seed-filling phase and a final harvest at maturity were conducted. During the seed-filling phase, sugar and α-amino-acid concentrations of seeds were not reduced by drought stress. Thus, assimilate availability was sufficient, pointing to no source limitation of seed development. The DNA content of the seeds was also not affected and pointed to no limitation of cell division. However, 40 days after flowering a reduction of cell extension was found. Consequently, a sink limitation occurred under drought stress. At final harvest, seed yield was significantly reduced under drought stress due to a lower single seed weight, whereas seed number per plant was unaffected. Oil concentration was not reduced by drought stress. Thus, oil synthesis did not limit oil yield. Consequently, a reduced oil yield under drought stress during the seed-filling phase was caused by a lower seed weight, which resulted from a decreased cell extension.     

How does the harvest index affect water‐use efficiency and nutrient‐utilization efficiency of sunflowers (Helianthus annuus L.)?

Besides oilseed rape and soybean, sunflower is one of the most important annual oilcrops. Apart from seed yield, which is the most important trait in many crops, oil yield is of utmost interest for sunflower breeders and farmers. Compared to the seed yield of sunflowers, their total biomass is often very high, and it is of great agronomic interest to increase the ratio of both parameters, which is defined as harvest index. With an increase in harvest index, improvements of resource‐use efficiencies can be expected. To generate an adequate seed yield, water and nutrients are key factors and their efficient use becomes increasingly important under conditions of aridity and higher production goals. A pot experiment was conducted in summer 2017 to determine differences in harvest index of various sunflower genotypes which could have an influence on the use efficiencies of water and nutrients (N, P, K). In total, 25 genotypes of different origin and with various morphological traits were investigated under optimal growth conditions. The harvest index varied from 29% to 47% and showed significant differences among some genotypes. The harvest index was less affected by the total biomass of the plants but more by the seed yield. The seed yield itself was mainly determined by the single seed weight rather than by the number of seeds. The experiment also confirmed significant positive correlations between harvest indices and all use efficiencies. Genotypes with high harvest indices were characterized by high oil concentrations in the seeds and particularly by high oil yields. In conclusion, cultivation of sunflower genotypes with high harvest indices most likely results in high water‐use efficiency and high nutrient‐utilization efficiencies as well as in high oil yields.     

Seed production and breeding potential of the fluted pumpkin,Telfairia occidentalis

Summary Studies during 1980–1987 relating to seed production of the fluted pumpkin (Telfairia occidentalis Hook. f.) are summarized. Essentially, the dioecious nature of the crop makes sex-ratios of plants affect the number of fruit-bearing females. Overall, about 50% of plants are female, of which some 15% are fruitless. Each fruit-bearing female has 1.5 fruits that contain 60 seeds. The mean weight of seeds is 15 g, and 74% of this total seed weight comprise the seed kernel which contains about 40% oil. Thus, a yield estimate of seed kernels reaches 1.9 t/ha; an output that is superior to that of most other oil seeds now being exploited for seed oil and cake in Nigeria. Measures to raise seed yields and the possibility of breeding work are discussed.     

萝卜-芥蓝异源四倍体的合成及GISH分析

通过萝卜(Raphanus sativus L.,2n=18,RR)与白花芥蓝(Brassica alboglabra Bailey,2n=18, CC)杂交,F1经秋水仙碱加倍合成萝卜-芥蓝异源四倍体（Raphanobrassica, 2n=36, RRCC）。经F₄~F₁₀代连续育性选择,F₁₀单株种子产量达32.3 g,每角粒数达14.9。基因组原位杂交显示F₁₀减数分裂行为类似于二倍体物种,表明该异源四倍体的细胞学行为已经稳定。育性观察表明,可育花粉足够各代生产种子,但低世代杂种出现高频瘪粒种子,胚珠败孕可能是其主要原因。该萝卜-芥蓝异源四倍体可以用作向油菜（B. napus L.,2n=38,AACC）转移萝卜基因的遗传桥梁。     

Linking participatory plant breeding to the seed supply system

There is a strong link between formal plant breeding and seed supply. In developed countries, it was the emergence of systematic plant breeding that generated new named varieties and stimulated organized seed multiplication and marketing by commercial companies. In developing countries likewise, the experience of the ‘Green Revolution’ in the 1960’s led to the establishment in the following decade of national seed projects which could deliver the products of plant breeding more effectively from breeder to farmer. The provision of a secure conduit leading from research to agriculture remains a major justification for formal seed systems. The limitations of formal breeding approaches have been recognized in recent years, especially for crops grown in marginal and diverse environments, where farmers’ requirements are more complex. This has prompted interest in alternative participatory plant breeding strategies in which farmers can play an active role in the selection process. There has been a parallel recognition of the role of the informal seed sector, as the major seed supplier in many crops and areas where the regular sale of seed by formal organizations is difficult. The question which arise therefore is—“How do participatory breeding approaches relate to both formal and informal seed systems?” The purpose of this paper is to examine the technical, regulatory and policy aspects of this question, with emphasis on the following issues:

• The nature and definition of participatory plant breeding (PPB) outputs,
• Maintaining the identity and integrity of PPB outputs
• The relevance of official variety evaluation and registration procedures
• Maximizing the diffusion and impact of PPB outputs
• Innovative seed supply systems linked to PPB activities
• The role of policy in facilitating alternative seed delivery systems

The synthesis of this discussion is that PPB initiatives must be linked to a secure diffusion strategy within and beyond the participating communities if the technical and social benefits of this approach are to be fully realized. National policies relating to seeds and regulatory frameworks must also take account of this approach to avoid downstream constraints.     

Market‐led options to scale up legume seeds in developing countries: Experiences from the Tropical Legumes Project

There are several hurdles to ensure sustainable seed production and consistent flow of improved legume varieties in sub‐Saharan Africa (SSA) and South Asia (SA). The unreliable demand, autogamous nature of most of the grain legumes, and slow variety replacement rate by smallholder farmers do not provide strong incentive for private seed companies to invest in legume seed business. Unless a well thought‐out and comprehensive approach to legume seed delivery is developed, current seed shortages will continue, eroding emerging market opportunities. The experiences reported here are collated through a 10‐year partnership project, the Tropical Legumes in SSA and SA. It fostered innovative public–private partnerships in joint testing of innovative market‐led seed systems, skills and knowledge enhancement, de‐risking private sector initiatives that introduced in new approaches and previously overlooked entities in technology delivery. As new public and private seed companies, individual seed entrepreneurs and farmer organizations emerged, the existing ones enhanced their capacities. This resulted in significant rise in production, availability and accessibility of various seed grades of newly improved and farmer demanded legume varieties in the target countries.     

The Influence of Row Spacing and Seeding Rate on Seed Yield and Yield Components of Forage Turnip (Brassica rapa L.)

The effects of four row spacings (17.5, 35.0, 52.5 and 70.0 cm) and five seeding rates (50, 100, 200, 400 and 800 viable seeds m^?2) on seed yield and some yield components of forage turnip (Brassica rapa L.) were evaluated under rainfed conditions in Bursa, Turkey in the 1998–1999 and 1999–2000 growing seasons. Plant height, stem diameter, pods/terminal raceme, total pods/plant, seeds/pod and primary branches/plant were measured individually. The number of plants per unit area was counted and the lodging rate of the plots was scored. The seed yield and 1000‐seed weight were also determined. Row spacing and seeding rate significantly affected most yield components measured. The number of plants per unit area increased with increasing seeding rate and decreasing row spacing. Plant height was not greatly influenced by row spacing and seeding rate, but higher seeding rates reduced the number of primary branches and the stem diameter. The number of pods/main stem was affected by row spacing and but not by the seeding rate. Also, the number of seeds per pod was not affected by either the row spacing or the seeding rate. In contrast, the number of pods per plant clearly increased with increasing row spacing, but decreased with increasing seeding rate. The plots seeded at narrow row spacings and at high seeding rates were more sensitive to lodging. Seeding rate had no significant effect on seed yield in both years. Seed yield was similar at all seeding rates, averaging 1151 kg ha^?1. However, row spacing was associated with seed yield. The highest seed yield (1409 kg ha^?1) was obtained for the 35.0‐cm row spacing and 200 seeds m^?2 seeding rate combination without serious lodging problems.     

Flowering, Pod Set and Reproductive Success in Soya Bean

Much of the variation in yield of soya bean [Glycine max (L.) Merrill] and other grain crops is associated with changes in the number of pods and seeds per unit area. Photosynthesis and seed characteristics are the primary determinants of pod and seed number, but recent research suggests that the temporal distribution of flower production may also play an important role. Soya bean has a long flowering period (up to 40 days or more), but most of the flowers are produced in a much shorter time. The length of the period varies among cultivars, growth habits (indeterminate and determinate) and environments. The reproductive success of flowers produced early in the period is usually greater than those produced later. Little is known, however, of the regulation of the temporal distribution of flower production or its potential role in determining pod and seed number at maturity. Research is needed to determine first, if the temporal distribution can be manipulated to increase pod and seed set and secondly, if such increases would result in higher yields.     

Uniformity, Performance and Seed Quality of Soybean (Glycine max (L.) Merrill) Seed Crops Grown from Sub-samples of One Seed Lot Obtained after Selection for Physical Seed Attributes

In a glasshouse experiment it was examined whether narrow grading and selection from a commercial soybean seed lot cultivar 'IAS-5', could improve the uniformity of the seed crop grown from it and thereby enhance yield, quality and uniformity of seeds produced. The classes created were: Control (original seed lot); Size-graded seeds (projected area measured by image analysis 37–46 mm²); Non-cracked seeds; Yellow seeds; Size-graded sound seeds (size-graded, non-cracked, yellow, non-wrinkled, non-etched). Compared to the control, percentage of emergence, survival and number of yielding plants were enhanced in crops from non-cracked, yellow or size-graded sound seeds. Differences in plant numbers did not result in differences in crop yield. The different seed lots also did not differ in crop uniformity: time interval between stages of plant development, plant height 20 days after sowing, yield components, physical or physiological quality attributes of seeds produced, and respective coefficients of variation were similar. Fewer plants survived in crops showing a larger variation in plant height 20 days after sowing, thus reducing differences in initial plant-to-plant variation. Creating more uniform crops by additional grading or selection of commercial seed lots may therefore not be promising.     

Public sector soybean (Glycine max) breeding: Advances in cultivar development in the African tropics

Formal public sector soybean breeding in Africa spans over four decades, and it was initiated by the International Institute of Tropical Agricultural (IITA). As the demand of soybean continues to outstrip production, strategic projects such the Tropical Legume (TL) were initiated, in which the main goal was to enhance the productivity of soybean in the farmers’ fields in Sub‐Saharan Africa. One of the strategies to enhance the productivity of soybean in the farmers’ fields is through developing and deploying improved soybean varieties in the target countries. Through the TL I and TL II projects, a number of varieties were released in the target countries, Kenya, Nigeria, Malawi and Mozambique by employing participatory variety selection (PVS). This review provides highlights of the achievements made by IITA breeding programme and insights of what needs to be done to enhance yield improvement for soybean in Africa using demand‐driven breeding approaches.     

杭白芍结实性状及籽油品质分析

分析杭白芍结实性状及其籽油品质,为芍药籽油专用品种培育及籽油开发利用提供理论参考。对杭白芍的结实性状相关性和籽油理化性质进行测试和分析,结果表明：（1）单心皮种子数和心皮长均与单株产量呈极显著正相关,蓇葖果数与单株产量呈显著正相关,分株数与单株产量呈显著负相关;主成分分析表明,前4个主成分累计贡献率达88.8768%。（2）籽油测试结果表明,种子含油率21.31%,油酸40.56%,亚油酸29.16%,亚麻酸22.11%,籽油不饱和脂肪酸91.83%,维生素E含量79.64 mg/100 g。因此,在选育高产品系时要重点关注单心皮种子数、心皮长和蓇葖果数等性状指标。杭白芍籽油具有较高的食用价值,可以作为一种新型的油料作物,具备深入研究推广的价值。     

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.     

早熟无限结荚习性大豆子粒生长特征

大豆产量潜力受到基因型和环境条件的制约。一种基因型的密度、植株分布决定其对太阳辐射、水分和养分的利用,进而高产的形成。当群体生长所需外界要素之一不能满足时,植株间形成竞争。产量的区域间及年际间差异与这种株间竞争关系密切,最终表现为单位面积内一个或多个产量构成因子的差异,如株荚数、荚粒数、或单粒重(籽粒大小)。本研究探讨籽粒大小在调节不同密度、行距条件下产量差异及年际间产量差异的作用。多点试验表明,籽粒大小在不同节位上及不同籽粒数的荚间差异不大。然而在2粒或3粒荚内,荚基部粒比中部及顶部粒小10%,而且子叶细胞体积差异不大。在改变源库、增强光照或遮阴条件下,籽粒大小发生变化。籽粒大小与子叶细胞数相关。籽粒大小是可塑的,但即使底部节位荚较顶部节位提前15~20 d鼓粒,籽粒大小在所有节位间差异不大,所以籽粒大小与子叶细胞数的关系仍值得探讨。     

The Physiology of Seed Germination in Groundnut (Arachis hypogaea L) Cultivar GG-2. I. Effect of Seed Size

The seeds of groundnut cultivar GG-2 were categorized according to their test weight (100 seed weight) as bold (58.2 g), medium (37.9 g), small (24.9 g), small wrinkled (13.4 g) and control (30.3 g) seed lot. The variation in their size and dimension was also taken into account. The overall germination percentage was high for medium size seeds and was closely followed by bold seeds. The performance of the small and small wrinkled seeds was comparable to that of control. The seed vigour was found to be higher with heavier seeds. Small seeds exhibited equally good performance in response to seed germination and growth of the seedling components. There were no significant differences for the development of hypocotyl, epicotyl and plumule.     

不同贮藏年限敖汉苜蓿种子活力及生理特性的研究

种子在贮藏过程中随着贮藏时间的延长出现老化现象,使种子活力下降、生理特性发生变化,从而降低种用价值.为探讨不同贮藏年限紫花苜蓿种子的活力变化,选择室温贮藏0～3年的敖汉苜蓿种子,比较分析种子劣变规律及生理特性的差异.结果表明:收获当年的敖汉苜蓿种子具有较高的硬实率,其抗逆性强,SOD、POD、CAT、MDA和脯氨酸含量最高,而发芽势和可溶性蛋白含量最低.贮藏起初2年,种子硬实率、不正常种苗数、死种子数、SOD、POD、CAT、MDA和脯氨酸含量降低,发芽率、发芽势和可溶性蛋白含量增加.随着贮藏时间的延长,种子可溶性蛋白含量降低,SOD、POD、CAT、脯氨酸和MDA积累量增加,种子质量下降,不正常种苗数和死种子数增多,种子活力下降.综合试验结果,贮藏2年有利于打破种子休眠,其种子质量最佳,种子发芽能力最强,但是种子抗逆性不高;贮藏1年存在轻度休眠,应进行打破硬实处理;贮藏3年的种子活力下降,其种用价值降低,不利于在人工草地建植中使用,生产中应贮藏2年后再播种效果较好.研究结果能较好地说明苜蓿种子在贮藏期间的活力变化,为我国人工草地建设中合理使用苜蓿种子提供理论依据.     

乙烯的生物合成与信号及其对种子萌发和休眠的调控

种子萌发是一种关键的生态和农业性状,由调控种子休眠状态和萌发潜势的内在和外部信息所决定,在植物随后的生长发育和产量中起着极其重要的作用。休眠是指种子在合适的条件下暂时不能萌发。乙烯是一种简单的具有多种功能的气体植物激素,在分子、细胞和整体植物水平调节植物的代谢。在适宜和逆境条件下,乙烯通过与其他信号分子的相互作用影响植物的行为。本文主要综述乙烯的生物合成与信号、乙烯在种子萌发和休眠释放中的作用以及乙烯与植物激素脱落酸和赤霉素的相互作用;并提出了需要进一步研究的科学问题,试图为解释乙烯调控种子萌发与休眠的分子机制提供新的研究思想。     

The Potential for Utilizing the Seed Crop Amaranth (Amaranthus spp.) in East Africa as an Alternative Crop to Support Food Security and Climate Change Mitigation

The projected growth in global food demand has resulted in increased attention towards underutilized crops with the potential to improve global food security and ability to mitigate adverse effects of climate changes. Changing consumer demands in favour of more nutritiously balanced and organically grown crops have added to the interest in species such as amaranth. Promoting the consumption and cultivation of amaranth could be valuable due to its unique nutrient composition and inherent tolerance of drought and other stress factors. Due to current and predicted effects of climate changes, these attributes are becoming increasingly important. Amaranth is a source of high quality protein, as well as dietary fibre and lipids rich in unsaturated fatty acids. The seeds contain desirable levels of minerals, vitamins for human diets, in addition to other bioactive components such as phytosterols, squalene, fagopyritols, saponins and polyphenols. Amaranth is currently in demand by specific consumer groups, such as high‐performance athletes, malnourished children, and people suffering from diabetes and coeliac disease. Even so, there are few detailed analyses available concerning the potential for using amaranth to improve and support agricultural productivity in developing countries. The present review has assessed the promotion and improvement of amaranth production in East Africa to hold subtstantial potential for benefitting small‐holder farmers in Africa, by providing a stable source of income and food for subsistence farmers, while also mitigating the impact of climate change through the prospect of supporting the establishment of food and nutritional security.     

华重楼种子预处理对其萌发特性的影响

目的:筛选华重楼种子最佳预处理方法,为生产上及早破除种子休眠,促进种子萌发提供指导.方法:新鲜的华重楼种子经不同去皮方式、不同层积基质及不同浸种药剂处理后,于18℃层积条件下进行发芽试验,每周观察并记录,比较分析种子的发芽率、发芽势、平均发芽天数的差异.结果:与带皮种子相比,冷冻去皮可显著缩短种子平均发芽天数,而砂搓、纱布、手剥去皮的种子发芽率和发芽势均有显著降低;与壤土基质相比,细砂、蛭石、木屑层积的种子发芽率及发芽势均有显著提高,且蛭石基质层积可显著缩短平均发芽天数;NaN3、H2O2、KNO3浸种处理均能显著提高种子发芽率.结论:华重楼生产上宜采用冷冻法去除种子外种皮,使用0.001％浓度的H2 O2浸种14 h后于18℃蛭石中层积.