The ingress of Poa annua into perennial ryegrass swards

The ingress of Poa annua into established swards of perennial ryegrass was recorded in four experiments aimed at determining whether ingress was due to P. annua aggression or to a decrease in ryegrass vigour. Emphasis was placed on severity of defoliation, effect of bare spaces and the time of year most favourable to colonization.
In Experiment 1, P. annua ingress was greatest in the autumn, especially where ryegrass had been sown in rows rather than broadcast sown. In Experiment 2, seedlings of P. annua only established successfully in mature ryegrass swards that had been defoliated at intervals of two weeks. Experiment 3 showed that ingress was inversely related to the vigour of the ryegrass cultivar, being particularly high on frequently defoliated plots. In Experiment 4, which involved a study of the colonization of poached areas, more seedlings established in quadrats surrounded by P. annua -dominant pasture compared with patches surrounded by perennial ryegrass.
It is concluded that P. annua is not an aggressive species; it colonizes only open ryegrass swards that have become weakened by intensive management.     

Planting date effects on flowering,seed yield,and oil content of rape and crambe cultivars

Both crambe (Crambe abyssinicia, Hochst) and rape (Brassica napus L. and Brassica rapus L.) are cool season crops, thus they may have potential as irrigated, winter rotational crops in the low deserts of the southwestern United States and northern Mexico. Currently, no information is available on the effects of fall planting date on the production of these crops. The objectives of this study were (1) to determine the effects of fall planting date on flowering patterns, seed yield, and oil content of crambe and two species of rape, and (2) to determine the suitability of rape and crambe as rotational crops for the low deserts of the southwestern United States. Nine cultivars of rape and one cultivar of crambe were planted at the Maricopa Agricultural Center on three dates in November and December of 1995 and four dates from October through December of 1997 on a variable Mohall sandy loam soil (fine-loamy, mixed hyperthermic, Typic Haplargid). Five of the rape cultivars were B. napus types and the remaining four were B. rapus. One was an industrial rape (R-500) and the other eight were Canola types. Seed yield, oil concentration, and seed weight were determined. In 1996, the percent of plants flowering was observed visually on a periodic basis. In 1998, detailed imaging of flowering was done periodically using a digital camera. Planting date affected water application by controlling the length of the growing season. Our plants were taller, oil content was higher, seed weights were comparable, days to flowering were more than doubled, and seed yields were lower than plants from spring plantings in the Northern Great Plains. In both years of the study, the highest yields were obtained when rape and crambe were planted in November, which would fit well with cotton harvest dates. Lodging was a serious problem in rape. Crambe was sensitive to frost and could fail in some years. Only R-500 matured early enough to be used in rotation with current cotton cultivars. In addition to the onset of flowering, the automated method for estimating flowering was able to detect differences between Brassica species and cultivars and to measure the duration of flowering. Each species had a distinctive flowering pattern. Planting dates also affected the pattern and efficiency of flowering. Reproductive efficiency appeared to change with planting date and in general, October and November planting dates produced seed with higher oil content and seed weights than December planting dates.     

The effect of photoperiod on flowering and TPS production in the warm tropics

Summary Three similar field experiments with five cultivars were carried out to evaluate the effect of a 5-hour extension of the natural daylength and a 3-hour night break on flowering and TPS production in the warm tropics. Shoot length, number of inflorescence positions per plant and number of flowers per inflorescence varied considerably between the experiments. In each experiment, the supplementary photoperiods delayed cessation of shoot growth and thereby increased the orders of branching and the number of inflorescence positions per plant. The photoperiod treatments significantly increased the number of flowers at the last produced inflorescence positions, but not at other ones. Pollen production and quality, berry set, seed set and 100-seed weight were not affected by the photoperiod treatments. TPS production was characterized by variability in flowering and low and variable seed production per flower.     

The effects of phosphorus and form of nitrogen supply on leaf cell size and nutrient content in Trifolium repens and Lotus uliginosus

White clover (Grasslands Huia) and lotus (Grasslands Maku) were grown in pots of soil at a range of phosphorus supply, and reliant on symbiotic nitrogen fixation (SN plants) or entirely on mineral nitrogen (MN plants). Shoots increased in weight with phosphorus supply. White clover MN shoots were bigger than those of SN plants except at the lowest level of phosphorus supply; lotus MN shoots were only bigger than SN shoots at the highest level of phosphorus supply. Leaf growth rate and size increased with phosphorus supply but were not significantly affected by the nitrogen treatments.
Estimates of cell size were made by determining DNA concentration, by digestion of tissue followed by counting and by taking vinyl impressions of epidermal cell surfaces. Lotus cells are bigger than those of white clover. 'Digested' cell sizes were not significantly affected by changes in phosphorus supply. Epidermal cell size increased with phosphorus supply, but the relationship was weaker in SN than in MN plants. Methods which give values for 'average' cell size are capable of detecting large-scale differences, but methods able to resolve cell heterogeneity are necessary for an accurate picture of the relationship between leaf growth and cellular nutrition.
Average concentrations of total and inorganic phosphorus on a DNA basis did not differ between the species, contrary to concentrations on a dry weight basis, indicating that differences in phosphorus efficiency can be partly explained on the basis of average differences in cell size. Differences in inorganic phosphorous on a DNA basis at higher levels of supply suggested an additional intrinsic difference in cellular accumulation of inorganic phosphorus between the two species.     

Observations on the effect of post-emergence application of ethofumesate on the shoot growth of Poa annua and Lolium perenne seedlings†

Swards of L. perenne and P. annua were treated at the 2–3 leaf stage with recommended rates of ethofumesate (5 and 10 kg a.i. ha^-1). P. annua ceased normal growth, became swollen at the shoot base and eventually showed signs of senescence. L. perenne showed no visible defects, treated swards being more vigorous than untreated. Scanning electron micrographs showed that the developing leaf primordia of P. annua had been affected by the ethofumesate. In both grass species, ethofumesate induced abnormalities in cell division. These abnormalities caused irreversible damage to P. annua but only slight distortion of L. perenne which later recovered and resumed normal growth. More detailed biochemical studies are required to determine the specific effects of ethofumesate on cell growth.     

牧草种子生产中落粒性的影响因素与防控技术

落粒性是牧草种子生产中的关键制约因素,通常造成无芒雀麦(Bromue inermis)、冰草(Agropyron cristatum)、老芒麦(Elymus sibiricus)、高羊茅(Festuca arundinacea)、草地早熟禾(Poa pretensis)、路氏臂形草(Brachiaria ruziziensis)等优良牧草种子严重减产。本文重点阐述了种子生产中影响落粒性的因素,种子落粒性对种子生产的影响,相关减少种子落粒性的研究进展及措施,为今后在生产中降低牧草种子落粒性提供参考。     

Relationship between assimilate supply per seed during seed filling and soybean seed composition

Developing soybean cultivars with high seed protein concentration has been hampered by the negative correlation between seed protein and seed yield. While previous in vitro studies have documented the impact of assimilate supply to the seed in determining seed protein, in planta studies generally have failed to link seed protein accumulation directly with assimilate supply per plant during seed filling. It may be possible to reconcile this apparent contradiction by expressing the relationship between seed protein and assimilate supply in planta on a per seed basis. We evaluated the association between seed composition and assimilate supply per seed in closely related experimental lines varying in seed protein concentration and in several elite varieties from the Iowa State University breeding program. High seed protein content was associated with greater leaf area per seed at R5.5, which was a consequence of fewer seeds set per plant. The more favorable source/sink ratio provided greater assimilate per seed during grain filling, but limited the yield potential of the high protein lines because of reduced seed set. Depodding during grain filling increased seed size of low protein lines and increased seed protein concentration to levels comparable to those in the untreated high protein lines. Seed size was far less responsive to depodding in the high protein lines. These results suggest that high protein lines maintain assimilate supply per seed at or near saturating levels during seed filling. Improving seed protein levels in high yielding varieties will require increasing assimilate supply per seed without sacrificing seed numbers.     

Photoperiod sensitivity after flowering and seed number determination in indeterminate soybean cultivars

Seed and pod numbers are the main yield components in soybean (Glycine max (L.) Merrill). They are related to canopy photosynthesis during a critical period, occurring between the R1 (beginning of flowering) and R6 (full seed) stages. We investigated the relationship between the duration of the critical period and the number of seeds produced. Response to photoperiod during post-flowering stages was evaluated in indeterminate soybean cultivars from maturity groups (MG) IV and V. The study was conducted under field conditions with two sowing dates (normal and late). Plants were grown under natural photoperiod throughout the experiment or exposed, from the R3 stage (beginning pod) onwards, to artificially extended regimes of 2 h longer than natural daylength. Duration of the R3–R6 period increased in response to the extension of photoperiod, and cultivars of MG V exhibited a stronger sensitivity to photoperiod than those of MG IV. Exposure to long photoperiods promoted node production, mainly in branches, and increased node fertility. Within each sowing date, the increased duration of R3–R6 under longer photoperiods was corresponded with increments in pod and seed number. Seed number was related to the duration of R3–R6, particularly when the length of the period was corrected for temperature differences between treatments. Seed number was also related to the integral of solar radiation during R3–R6. The possibility of using sensitivity to photoperiod after flowering as a criterion for increasing yields through increasing seed number are discussed.     

Dynamic changes of nutrient content in herbaceous peony seed

Herbaceous peony is a promising oilseed crop. ‘Hangshao’ and ‘Fenghuang Niepan’ are two cultivars with high yield and oil content. In this study, seed reserved nutrient of these two genotypes were investigated during seed development process. Results showed that ‘Hangshao’ and ‘Fenghuang Niepan’ matured approximately 85 ​d after flowering (DAF). The development process could be divided into four stages: seed formation and enlargement stage (S1), seed inclusion and enrichment stage (S2), crude fat rapid accumulation stage (S3) and dehydration and color transition stage (S4). During this process, 100-seed fresh weight (HFW) and 100-seed dry weight (HDW) increased, whereas water content (WC) decreased. HFW, HDW and WC for ‘Hangshao’ seed at 85 DAF were 28.56 g, 20.78 ​g and 37.50% respectively, whereas those for ‘Fenghuang Niepan’ seed were 27.2 ​g, 19.78 ​g, and 30.85% respectively. In terms of the primary metabolites measuring, soluble protein content was consistently low (only 2.24%–3.15%), while starch content was relatively high (5.60%–24.81%). They displayed a trend of gradual increasing in early stage, followed by rapid decline. Crude fat tended to accumulate continuously with a linear upward trend starting at 40 DAF, and its maximum level was reached at 85 DAF (27.57% for ‘Hangshao’ and 29.57% for ‘Fenghuang Niepan’). For the secondary metabolites determination, total phenols content was relatively steady, maintaining at 107.7–129.9 ​mg/g for both cultivars, while total flavonoids content varied within 25.33–65.33 ​mg/g for ‘Hangshao’ and 24.33–52.37 ​mg/g for ‘Fenghuang Niepan’. The maximum level for both cultivars occurred at 55 DAF. Furthermore, crude fat content was found to be highly correlated with WC by correlation analysis and linear regression model definition (P ​≤ ​0.01 and r ​= ​0.954). Thus, WC was recommended for evaluating crude fat in peony seed. These findings could provide scientific reference for high-yielding production practice for oleaginous peony plant.     

Predicting seed admixture in maize combining flowering characteristics and a Lagrangian stochastic dispersion model

The seed purity problem has received very low attention in maize coexistence studies, and has not been considered in prediction tools that simulate pollen flow and out-crossing between maize fields. To fill this gap we developed the Seed Admixture Model (SAMETH) able to predict seed admixture dispersion combining flowering characteristics (pollen shed, silks exertion) with a Lagrangian stochastic dispersion model. The model was tested with a dataset obtained from 20 fields in 2007 and in 2008, whose seeds were mixed with 1% of a homozygous blue-kernelled hybrid. The model was first calibrated with data from 6 fields and then validated with the data from the remaining 14 fields. Moreover, a sensitivity analysis was performed to test the consequences of different pollen quantities released by the admixture and the commercial hybrids. The measured seed admixture ranged from 0.7% to 6% and the model was able to simulate the seed admixture with r² = 0.83. The sensitivity analysis showed that the model was sensitive to the absolute released pollen quantities but it was still able to predict seed admixture rather accurately. Because of its reliability, the model could become a useful tool for case study scenarios that involve seed admixture and for which field implementations would be too complex and time-consuming.     

The effects of dihydroquercetin on the cut surface of seed potatoes

The purpose of this study was to determine the effects which dihydroquercetin (DHQ) has on the natural healing process of suberization and wound periderm initiation in cut seed potatoes. Dihydroquercetin is a phenolic compound extracted from the bark of Douglas Fir,Pseudotsuga menziesii (Mirb.) Franco. Anatomical studies of treated seed potato tissue showed that treatment with bark-383, the cork-rich fraction of the whole bark containing approximately 2% pure DHQ, increases the thickness of the suberized layer formed below the cut surface. Treatment with 4% bark fraction I, which is blended to that concentration with the inert carrier dust Pyrax and contains approximately the same amount of DHQ as does the bark-383, also promoted the formation of a thicker layer of suberized cells. The thickness of the wound periderm did not significantly vary as a result of the use of any treatments containing DHQ. The use of Captan (Orthocide 50W) as a cut seed treatment in these studies was found to inhibit the formation of a suberized layer and subsequently the initiation of a wound periderm. The combination of bark-383 and Orthocide 50W in a treatment mixture reversed the inhibitory affect of the Orthocide 50W alone and therefore allowed for the formation of a well suberized layer and a wound periderm. It was found that wound healing on the cut surface of seed potatoes is largely dependent on the type of tissue present at any given point on that cut surface. Therefore, the response to treatment of the stolon end, center, and blossom end tissues was related to the type of tissue which was present in each of those tuber regions. The fungal mold growth on treated seed pieces incubated in a controlled environment was adequately retarded when Orthocide 50W was combined with bark-383 in a mixture ratio of 1:9 respectively. The longer the treatment material was allowed to remain on the seed piece, the greater was the protection against mold growth afforded by the mixture.     

佳木斯地区大豆种子繁殖与经营对策研究

本文对佳木斯地区近年来大豆种子生产和销售情况进行了论述,介绍了大豆生产、品种布局、主导品种的应用和种子生产销售存在的问题,并提出了解决对策。     

棉花杂交种的高产优质制种技术

棉花杂交制种是通过人工去雄授粉获得杂交种子,工作量大,制种成本高.详细介绍了棉花杂交种高产优质制种技术的方法和步骤,按此技术实施,可以降低生产成本,提高棉花制种质量和制种水平,收获高产优质杂交种.     

Genotypic and environmental effects on lupin seed composition

Currently, white lupin (Lupinus albus L.) is gaining importance due to its high nitrogen fixation capability and potential in sustainable crop production systems. Even though research conducted in Australia, Chile, Germany, New Zealand, and Portugal has indicated lupin's positive potential as human and animal food, such information from Virginia and adjoining areas of the United States is not available. In addition, effects of growing environment and genotypes on lupin seed composition need to be characterized to evaluate lupin's potential as a food and feed crop. Towards this end, seed of 12 lupin genotypes produced in Maine (USA) and Virginia (USA) were compared to determine genotypic and environmental effects on contents of protein, sugar, oil, various fatty acids, amino acids, and minerals. The protein content of dry seed was not affected by growing environment. However, growing environment had significant effects on contents of total sugar, amino acids, oil, fatty acids, and minerals. Significant variation existed among 12 lupin genotypes for various traits when composition of seed produced in Virginia was evaluated. The results indicated that site-specific evaluation of adapted lupin genotypes for chemical composition should be included in efforts to evaluate lupin's overall potential as a food or feed crop.     

Seed producer cooperatives in the Ethiopian seed sector and their role in seed supply improvement: A review

The role of seed producer cooperatives (SPCs) in the Ethiopian seed sector and their contribution to seed supply improvement have received attention from researchers, policymakers, and development partners. However, limited work has been done in reviewing and documenting their involvement in the seed sector development. In this paper, we review and discuss the SPCs in the Ethiopian seed sector. Specifically, we reflect on the contribution of SPCs to improving seed availability and access in the country. The current liberal market system of Ethiopia creates new opportunities for growth as successful enterprises, but also brings new challenges, such as more intense competition for smallholder producers. The government policy encourages SPCs to engage in seed business. We draw on scientific literature, reports, white papers, project documents, and websites. The review reveals that the seed sector in Ethiopia consists of three seed systems: formal, informal, and intermediary seed systems. Each seed system has a specific contribution to the delivery of seed to farmers, but they vary in their approach and respective strategies. The SPCs are categorized in the intermediary seed system because they have features of both formal and informal seed systems. They play a key role in meeting seed demand and contribute greatly to seed supply improvement through high-volume production of seed, crop, and variety diversification, and seed delivery to farmers. They produce and market the seed through various market channels, including direct sales to farmers, sales through contractual agreement, and sales directly to institutional buyers. Their contribution to improving the seed supply and seed security has received considerable recognition by policymakers and development practitioners. Therefore, government and development partners should support and strengthen SPCs to maximize their success in the seed business and their contribution to improving the seed supply in Ethiopia.