Development of the male gametophyte of an infertile plant Armoracia rusticana Gaertn.

Horseradish, Armoracia rusticana , is propagated vegetatively through root cuttings. It is described as a male-sterile plant as it does not form seeds or only develops them in small quantities. This study discusses the anatomical structure of anthers and the events throughout meiosis up to the formation of a male gametophyte. Microscopic observations have shown that the anatomical structure of the anther wall of A. rusticana is typical of the whole family of Brassicaceae , and all its layers are properly developed and fully functional. Meiosis in the sporogenous tissue proceeds correctly and leads to the formation of microspores. Also the configurations of the cytoplasmic skeleton are typical of plants with simultaneous cytokinesis. Further development, however, exhibits many abnormalities. A majority of the cells formed in the sample studied were dysfunctional uninucleate microspores with apparent symptoms of degeneration of the cytoplasm and organelles. Binucleate pollen grains, in which mitosis did occur, constituted only 10% of the cells analysed. Anatomical and cytological observations of male sterility in A. rusticana indicated inhibition of development at the microspore, stage which was manifested by cytoplasm degeneration with a low number of membranes and a scarce amount of starch in proplastids. Usually, in the prolonged microspore stage and in the young pollen no mitosis occurs at the time of anthesis. Cytological disorders may, to a great extent, limit the number of functional bicellular male gametophytes. Both in microspores and in pollen grains, there is exceptionally little starch in plastids.     

The effects of cis-trans ABA on embryo germination and seed dormancy in wheat

Pre-harvest sprouting of wheat grain can cause economic losses especially in cultivars with low levels of seed dormancy. The aim of this study was to determine genotype differences in embryo sensitivity to germination in response to exogenous (+/–) cis-trans ABA treatments at different concentrations. Six white and four red seed-colored bread wheat genotypes that differed in dormancy were grown in a field near Swift Current, Saskatchewan in 2000 as a randomized complete block design with four replicates. The seed samples from this experiment were germinated in a controlled environment at 20 °C without light. The exogenous ABA treatments were 0 μM – whole seed (control), 0 μM-embryos, 25 μM – embryos and 50 μM – embryos. The ABA experiment was a factorial design with four randomized complete blocks with four ABA treatments in all combinations with the ten genotypes. A weighted (by day) germination index (WGI) was calculated for each genotype in each ABA treatment. Genotypes differed in response to ABA. The genotypes, ABA concentration and genotype by ABA concentration interaction effects were significant (p ≤ 0.05). Excised embryos showed significantly decreased dormancy in most of the experimental genotypes. The addition of exogenous ABA enhanced embryo dormancy of most genotypes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Spike formation and seed setting of the main stem and tillers under post-jointing drought in winter wheat

To clarify the influence of post-jointing drought on the ear-bearing and seed-setting characteristics of the main stem and tillers of winter wheat (Triticum aestivum L.), a pot experiment was conducted with cultivars “Shannong 29” (SN29) and “Heng 0628” (H0628), and five water regimes: mild drought (WR1) and severe drought (WR2) for 0–5 days after jointing, mild drought (WR3) and severe drought (WR4) for 0–10 days after jointing and adequate water supply as a control (CK). The present study focused on primary tillers (appear in the axils of main stem leaves: T1, T2, T3, T4, etc.), as well as on secondary tillers (appear from the bud in the axil of the prophyll: T10 and T20; appear in the axil of the first leaf of the primary tiller T1: T11). The yield components of tillers showed a downward trend with increasing tiller position and drought degree and duration, and the kernels per spike, single kernels weight and grain yield per spike of tillers T2, T3, T10 and T4 decreased more than those of the other tillers. These outcomes may be related to the spike developmental stages at the time of the drought period. Severe drought during the period from when the stamen primordium is first present (Waddington’s stage 4) to when the carpel extends around the three sides of the ovule (Waddington’s stage 5) significantly decreased the seed set of tillers, but short-term (5 days) mild drought during this period and even a short-term severe drought before Waddington’s stage 4 had little effect on the seed set of tillers. The ear-bearing capacity of tillers was determined not only by the spike developmental stage, but also by the gap from the main stem and the competition of nutrition and space between tillers. Although the ear-bearing rate of tillers T3 and T10 decreased rapidly after the short-term mild drought, the increase in the ear-bearing rate of tillers T20 and T11 effectively compensated for the loss of the number of spikes per plant. Therefore, the short-term mild drought at the jointing stage had no significant effect on the grain yield of the two cultivars. The tillers T2, T3, T10 and T4 were sensitive to soil moisture in the jointing stage and had high plasticity. During this period, if timely irrigation improves soil moisture, it is expected to increase the ear-bearing rate and seed set of these tillers, thereby increasing grain yield.     

The traditional inexplicable replacement of seed and seed ware of landraces and cultivars: A review

A review is presented on the often inexplicable seed replacement by farmers. Such a seed replacement has been mentioned since Biblical times and earlier. It occurred and still occurs all over the world and for all cultivated plants. In order to find out whether or not this seed replacement has some meaningful background, farmers in those areas where this type of seed replacement still takes place should be interviewed. Maybe, this seed replacement is based on farmers' experience since times immemorial in which farmers obtained (or believed to obtain) lower yields if seed is not replaced. If so, the cause of this type of seed replacement can be explained. This revised version was published online in August 2006 with corrections to the Cover Date.     

A molecular and embryonic study of apomixis in cassava (Manihot esculenta Crantz)

In cassava, apomixis fixes heterosis and avoids transmission of systemic pathogens which complicate vegetative propagation of the crop. A combination of evidence from maternal inheritance of RAPD markers and the structure of the embryonic sac in large progeny sets of two distinct genotypes have further confirmed the occurrence of apomixis in cassava. We could advance further on earlier reports of the detection of apomixis in four ways: (1) we could arrive at an estimate of the rate of facultative apomixis in the range of 2%; (2) we detected the occurrence of apomixis in a second genotype, derived from a different interspecific cross; (3) apomictic behavior was demonstrated in an F₁ individual and (4) parallel embryonic evidence was generated that corroborate the potential occurrence of apomixis by apospory. The fact that apomixis was detected in an F₁ interspecific hybrid hints to the possibility of directly transferring genes for apomixis from a wild relative to cultivated cassava. This revised version was published online in July 2006 with corrections to the Cover Date.     

Chemical induction of apomictic seed formation in maize

Summary Silks of 18 maize (Zea may L.) F₁ hybrids were treated with different combinations of 9 growth regulators, colchicine, and dimethyl sulfoxide (DMSO) for the purpose to induce apomixis (agamospermy) in 1988 and 1989. Hybrid K301 × K303 gave the highest (0.36%) average frequency of seed induction among the hybrids. The most effective treatments were DMSO, gibberellic acid plus 6-benzyl aminopurine (6-BA), and DMSO plus methanesulfonic acid. Individually, the highest frequency of seed induction was 1.4% for hybrid K731×K306 when treated with -naphthalene acetic acid (NAA)-zeatin mixture. The frequency of seed induction seemed to depend partially on the interaction between chemicals and hybrids. Cytological observation of root-tip cells indicated that the majority of the seeds obtained were diploid, some were mixoploid, and a few were haploid. Diploid plants from induced seeds from the same parent were morphologically uniform and resembled the parent. Variations in plant and ear heights were comparable to those of the hybrid parent. Cytological and morphological investigations suggested that the chemically induced seeds originated mainly from somatic tissue but occasionally came from reduced cells in the embryo sac, leading to haploids. The results showed that chemical induction of adventitious embryony in maize hybrids is possible, but the more effective chemicals, their concentrations, and ways of application for increasing the frequency of seed induction need to be explored for practical use.     

The progamic phase in Cichorium intybus L. Pollen tube growth in the style,incompatibility reaction and gametophytic competition

Summary Pollen germination and tube growth were studied following compatible, incompatible and pseudo-compatible pollinations in chicory. Pollen germination begins 3 minutes after compatible pollinations. The earliest pollen tubes reach the ovary 17 minutes later. Many of the later germinating pollen tubes are arrested and burst at the stigma papillae. In the transmitting tissue inhibitional effects due to negative interactions between pollen tubes are frequently observed. Complete self-incompatibility results in total inhibition of germination. In case of pseudo-self-compatibility, some pollen germinate but germination and stigma penetration are delayed and often result in pollen bursting. There is no self-incompatibility reaction in the transmitting tract but if the pollen tubes reaching this tissue are relatively numerous, negative interactions between them occur as after compatible pollinations. An hypothesis is presented which attributes the negative interactions between pollen tubes to the diffusion of a substance from the growing pollen tubes. This substance would also provoke pollen bursting on the stigma.     

植物激素和微肥对棉属(Gossypium)远缘杂种胚囊发育的影响

在棉属远缘杂种低世代植株生长发育过程中,定期喷施4～6次激素或与微肥混用,对促进胚囊发育有良好效果。喷施40mg/kg GA_3,80～100mg/kgNAA 或100mg/kg IAA 对提高杂种植株正常发育的胚囊%、单株铃数、铃重和单铃种子数均有良好作用,0.05～0.1mg/kg BR 和2mg/kg ABA 的效果也较好。2mg/kg ABA 或40mg/kg GA_3分别与3种微肥混施的处理中,以与 MnCl_20.1%混施处理表现突出,其正常胚囊%与对照比较均达显著水平,单施 MnCl_2效果不明显。     

Combining ability of seed vigor and seed yield in soybean

Studies have shown no consensus in relationships between seed yield and vigor in soybean [Glycine max (L.) Merrill]. The lack of information regarding the inheritance of seed vigor prompted this study to determine the types of gene action and combining ability estimates for seed vigor and its related traits. Five high and six low seed vigor soybean genotypes were crossed in a diallel, and selfed to produce 55 F₂ progenies, which were examined, along with the parents, for seed vigor, yield, and seed weight. Significant genotype and environment effects were found for seed vigor and yield. General combining ability (GCA) effects for seed vigor and seed yield were significant (p≤ 0.01) and larger than specific combining ability (SCA) effects. Significant GCA and SCA effects were found for seed weight, indicating that both additive and non additive genetic effects were involved in conditioning seed weight. The ratios of mean square, 2GCA / (2GCA+SCA), were 0.96 for seed vigor and 0.93 for seed yield. These ratios indicated that additive gene effects were more important than non additive gene effects for seed vigor and seed yield in these crosses. Mean seed vigor(83.8%), as determined by accelerated aging germination, and mean seed yield (2,155 kg ha^-1)in high vigor × high vigor crosses were higher than the high vigor × low vigor and low vigor × low vigor crosses. Mean percent accelerated aging germination rates in F₂ populations from diallel crosses were significantly related to mid-parent seed vigor(r² = 0.52^**) and midparent seed size (r² = 0.31^**). These results indicated that levels of seed vigor can be improved through breeding, while maintaining high yields because of the predominance of GCA effects in both seed vigor and seed yield. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic control of seed weight and calcium concentration in chickpea seed

Chickpea, Cicer arietinum L., is a staple protein source in many Asian and Middle Eastern countries. Hence, the mineral content of its seed, especially that of calcium, is of nutritional importance. Calcium is transported through plants and to legume pods almost exclusively via the xylem stream, with Ca accretion in developing seeds resulting primarily from diffusion of Ca from the adjoining pod wall. Thus, for seeds of differing surface‐to‐mass ratios, Ca concentration is expected to correlate inversely with seed weight. The relationship between seed weight and Ca concentration in chickpea seeds was studied using a range of germplasm and derivatives from crosses between types differing in seed Ca concentration. Among the cultivars tested, low seed mass was associated with high Ca concentration. However, the study of hybrid progeny indicated that seed Ca content was mainly determined by genetic factors other than grain weight genes. This finding may assist in future breeding of high nutritional quality chickpea cultivars.     

SSR标记技术在杂交水稻和杂交玉米种子质量鉴定中的应用研究

SSR标记具有快速、稳定、准确的技术优势,已经在品种鉴定等方面得到广泛的应用。为了鉴定生产用“两杂”种子样品的遗传多样性及纯度,利用36对SSR引物对39份杂交水稻样品进行了遗传多样性鉴定,其中2个样品为“同名异种”（遗传距离为0.11）,有2个样品疑似“异名同种”;利用33对SSR引物对36份杂交玉米样品进行了遗传多样性鉴定,同样存在“同名异种”和“异名同种”现象。在人为混杂的杂交水稻样本中,SSR标记检测值与实际混杂率u测验没有显著性差异;同时利用SSR标记和田间鉴定方法比较种子公司提供的10个杂交水稻样品纯度,尽管有3个样品SSR标记检测结果低于田间鉴定,但由于田间纯度鉴定以农艺性状为标准,遗传背景相似的单株难以区分,因此从加强种子质量监管角度考虑,SSR分子标记鉴定技术更为有利。     

Compatibility and incompatibility in witloof-chicory (Cichorium intybus L.). 1. The influence of temperature and plant age on pollen germination and seed production

Summary For the production of inbred lines and F₁ hybrids in witloof-chicory information is wanted on characteristics such as the incompatibility system. These characteristics can only be studied properly if the influence of temperature and physiological status of the plant on pollen germination and seed production is known. Investigations were carried out with 9 self-incompatible (SI) and 6 self-compatible (SC) clones in glasshouses of the IVT phytotron at constant temperatures of 10, 14, 17, 20, 23 and 26°C. In general, in vivo pollen germination percentages were rather low after self pollination with an optimum for germination around 17–20°C. No seeds were formed at the lowest temperature (10°C) while seed production for SC clones was usually (rather) good at higher temperatures. At 26°C seed production in some clones decreased. Both pollen germination and seed production decreased at the end of the flowering period. There was a rather positive relationship at e.g. 17 and 20°C between pollen germination after selfing and seed production. When no pollen germination was observed, no seed formation occurred. When pollen grains did germinate, seed development would not necessarily occur in all cases. So this relationship only enables negative mass selection for SC.     

Mapping and analysis of QTLs related to seed length and seed width in Glycine max

Both seed length and seed width are important traits for soybean yield. In the present study, 89 Quantitative trait loci (QTLs) of seed length and 65 QTLs of seed width were collected from published papers and our study. QTLs in this study were evaluated by the soymap2, then totally 23 consensus QTLs were located on 17 linkage groups (LGs) through the meta‐analysis. The minimum confidence interval was 0.28 cM and the mean phenotypic variance (R²) was ranged from 5.33% to 23.36%. To optimize these QTLs based on statistic analysis, overview method was further used to narrow down CI, the number of QTLs was narrowed down to 84. Furthermore, 2,750 candidate genes were screened from the consensus QTL intervals by informatics, a total of 37 genes were found to be associated with seed size. All results could lay a foundation for MAS (Molecular Assisted Selection) and gene cloning.     

Temperature effects on seed germination and expression of seed dormancy in wheat

Because preharvest sprouting decreases quantity and quality of wheat grain, researchers need effective protocols to assess response to preharvest sprouting conditions. The aim of this study was to determine which temperature gives the greatest difference in seed germination and expression of seed dormancy in 10 spring wheat genotypes. The genotypes were grown in the field near Swift Current, Saskatchewan in 2000 in a randomized complete block with four replicates. Seed samples were harvested at approximately 25% moisture content (wet weight basis) and dried to 12% moisture content with minimal after-ripening. Germination was under controlled environment at temperatures of 10, 15, 20 and 30 °C in darkness. A weighted germination index (WGI) was calculated. The analysis of WGI, for each temperature, showed highly significant (p ≤ 0.01) genotype effects on germination. Most genotypes decreased in WGI (increased dormancy) as temperature was increased from 10 to 30 °C. The greatest differences in seed germination tended to be at 15 °C and 20 °C. The level of seed dormancy depended on the genotype and germination temperature. This revised version was published online in August 2006 with corrections to the Cover Date.     

Use of immature seed germination and single seed descent for rapid genetic gains in pigeonpea

Long duration required for generation advancement in pigeonpea [Cajanus cajan (L.) Millsp] is one of the major bottlenecks in realizing rapid genetic gains. Therefore, a technology for rapid generation turnover is warranted to facilitate the development of new cultivars and recombinant inbred lines. Breeding of early‐maturing cultivars has now opened up the possibility of rapid generation advance (RGA) in this crop. This paper reports the development of an RGA technology that integrates the germination of immature seeds with single seed descent method of breeding. The results showed that immature 35‐day‐old seeds can be used successfully to turn over a generation of pigeonpea with 100% seed germination. These way 3/4 successive generations can be grown within a year. The methodology presented in this study will accelerate the breeding process for breeding cultivars and develop rapidly the materials required for genomics research in pigeonpea.     

Genetic variability for seed oil content and seed index in some wild species and perennial races of cotton

A 3‐year study was made on genetic variability of seed oil content and seed index with 20 wild species, two cultivated species and six perennial races of Gossypium arboreum cotton maintained at the Central Institute for Cotton Research, Nagpur, India. The mean seed oil content varied from 10.26 to 22.89% in 22 species of Gossypium and six races of G. arboreum. In this material the weight of delinted seed varied from 43.33 to 54.54 mg/seed. The highest seed oil content was recorded in the species G. lobatum followed by G. harknessii. On average, for both traits, the means were higher for G. arboreum and its races. However, G. africanum and G. harknessii reached the level of G. arboreum and its races for seed weight, while five wild species surpassed the best races and G. arboreum in seed oil content, among them was G. harknessii. To breed simultaneously for seed oil content and seed weight, crosses between races of G. arboreum and wild species of Gossypium seem to be promising.     

Seed formation in triploid loquat (Eriobotrya japonica) through cross-hybridization with pollen of diploid cultivars

As the fruits of loquat (Eriobotrya japonica, 2n = 2x = 34) carry large seeds, the breeding of seedless loquat has long been a goal. The recent creation of triploid cultivars (2n = 3x = 51) and the application of gibberellins allow commercial production of seedless loquat, but the possibility of seed formation in triploid loquats has not been carefully investigated. Through crossing experiments and cytological observations of meiosis and pollen tube growth, we found that the triploid line 3N-N28 was essentially self-sterile, but developed seeds on pollination with pollen from diploid cultivars at rates of up to 5.5%. Almost half of the seedlings survived to 5 months, and carried diploid (2n = 34), tetraploid (2n = 68), or aneuploid chromosome numbers. Our results suggest that triploid loquat cultivars might retain the risk of seed formation. Protection from pollination by diploid cultivars or the development of new triploid cultivars will be necessary to ensure the production of seedless loquat fruits.     

Genetic variation for secondary seed dormancy and seed longevity in a set of black‐seeded European winter oilseed rape cultivars

Secondary seed dormancy in oilseed rape is a phenomenon that allows seeds to survive in the soil for many years without germination. Following soil cultivation, dormant seeds may germinate in subsequent years, and they are the main reason for the occurrence of volunteer oilseed rape plants in successive crops. Inheritance of secondary dormancy may be related to seed longevity (SL) in the soil. Genetic reduction in secondary dormancy and SL could provide a mean to reduce the frequency of volunteer plants and especially the dispersal of transgenic oilseed rape. The aim of the present study was to analyse secondary dormancy, germination rate and SL of 28 black‐seeded winter oilseed rape cultivars using in vitro laboratory tests. The material was tested in field experiments at six different locations in Germany in 2008/2009. Significant effects of the genotype and the location on all traits were found. Heritability was high for secondary dormancy (0.97) and moderate for germination rate (0.70) and SL (0.71). Results indicate that a selection for low secondary dormancy would be effective.     

Evaluation of microspore-derived embryos as models for studying lipid biosynthesis in seed of rapessed (Brassica napus L.)

Summary Microspore culture of rapeseed (Brassica napus L.) has provided a powerful tool not only for breeding but also in developmental studies. In this study, microspore-derived embryos (MDE) of B. napus were evaluated as a model in seed for studying accumulations of triacylglyceride (TAG) fatty acids in both a low and high erucic acid rapeseed line; and accumulations of TAG and free fatty acids (FFA) in a high erucic acid rapessed line. The accumulation patterns confirmed that MDE had a similar TAG fatty acid profile to seed during the embryo development within each genotype. The oil accumulation in MDE after 36 days in culture (DIC) approached levels similar to those in zygotic seed 25 days after flowering (DAF). Significant differences were detected in contents of both total free fatty acids and specific free fatty acids between MDE and seed. During the developmental period, total free fatty acids changed from 16% to 2.1% in MDE, but from 10.5% to 0.1% in seed. MDE had much higher percentage of free linolenic and erucic acids than seed, particularly during the late developmental stages. The current study indicated that MDE can be used as a model to study TAG and TAG fatty acids in seed but caution must be taken to study free fatty acid metabolism.     

铁皮石斛不同外植体组培快繁技术比较研究

运用铁皮石斛不同的外植体进行组培繁殖研究,选择出适宜当前中草药发展合理的繁殖途经。本研究以铁皮石斛种子及茎段为外植体进行组培快繁技术试验,结果表明,二者在诱导初始条件、增殖方式、增殖系数、继代周期、根的诱导分化及苗木移栽等方面存在差异。通过比较试验认为,铁皮石斛快繁体系建立以茎段外植体为宜,建立的繁育体系具有经济高效稳定等优点,为规模化育苗提供物质和技术参考。