Seed-yield and yield components response to source-sink ratio in annual and perennial species of Lesquerella (Brassicaceae)

Although the annual Lesquerella fendleri is the prime candidate for the development of a lesquerolic rich oil-seed crop, within this genus there are other species available to breeders, some of which are perennials. However, the feasibility of a perennial crop of Lesquerella is not clear because increases in seed-yield tend to reduce perennially. The objective of this work was to determine the effect of the source-sink ratio on seed yield and yield components in annual and perennial species of Lesquerella. We predicted that (i) due to differences in allocation patterns of annual and perennial species, seed-yield and yield components in perennials would be less affected by the source-sink ratio (higher stability) than in annuals and (ii) since seed-weight has been found to be the most stable yield component in other crops and their wild relatives, most of the variation in seed-yield as a consequence of source-sink ratios would be determined by changes in the number fruits per plant and the number of seeds per fruit. A field experiment was carried out in Chubut, Patagonia Argentina in a complete randomized design with four treatments to examine source-sink relationships in four species of Lesquerella, two annuals (L. angustifolia, L. gracilis) and two perennials (L. pinetorum, L. mendocina). We used either shading (reduction of source) or removal of flower-buds (reduction of sink) to develop a range of source-sink relationships. All four species showed a similar yield response to source-sink variations. Seed-yield was lower in shaded plants, although the timing of shading influenced this response. Flower-bud removal resulted in a significant increase in seed-yield. Seed-yield differences among source-sink treatments were best explained by changes in the number of fruits per plant than by the number of seeds per fruit. Source-sink manipulations had no affect on seed weight. Flower-bud removal significantly increased the number of fruits per plant in all species except for L. mendocina. The number of seeds per fruits increased only in L. pinetorum. Our results show that carbon stored during pre-anthesis plays a key role in reproduction both in annual and perennial Lesquerella. The increase in the seed-yield components found with bud removal could potentially reduce longevity in perennial species. The results also show that the number of fruits per plant is a good proxy for seed-yield within a species.     

美国玉米品种命名规则探析及启迪

品种是种子企业的生命线,品种名称也就逐步构成了企业的无形资产。没有一套科学合理、系统持续的品种命名系统,难以打造出知名企业品牌,也会导致销售混乱及统计模糊。本文对中、美两国种业农作物品种命名规则进行分析与探讨,分析美国品种命名规则与经验,针对中国种业存在的问题,对玉米审定品种、参试组合、成型自交系的命名规则提出建议。     

Dynamics of reproductive growth of lesquerella (Physaria fendleri) over different planting dates

Vegetative and reproductive growth information of lesquerella (Physaria fendleri), a new oilseed crop targeted for bio-products, is important to understand especially in the early commercialization stage of this new crop. The objective of this study was to determine the effect of fall, winter, and spring planting dates over three years on the ontogeny of the crop including biomass, floral buds, flowers, and siliques. Fall plantings always produced more than the other plantings due to the extended season. Winter and spring plantings had less biomass and produced fewer buds, flowers, and siliques. The compensation of lower crop management costs and a shorter growing season could make winter a viable option for planting in the southwest. Spring planting could become viable if seed shatter due to summer rains could be reduced. The information will help decide growing regions suitable for crop production and determine what reproductive stages could be manipulated to improve seed yields.     

Popcorn (Zea mays L. var. everta) yield and yield components as influenced by the timing of broadcast flaming

Farmers are interested in producing popcorn under organic production systems and propane flaming could be a significant component of an integrated weed management program. The objective of this study was to collect baseline information on popcorn tolerance to broadcast flaming as influenced by propane dose and crop growth stage at the time of flaming. Field experiments were conducted at the Haskell Agricultural Laboratory of the University of Nebraska, Concord, NE in 2008 and 2009 using five propane doses (0, 13, 24, 44 and 85 kg ha⁻¹) applied at the 2-leaf, 5-leaf and 7-leaf growth stages. Propane was applied using a custom-built research flamer driven at a constant speed of 6.4 km h⁻¹. Crop response to propane dose was described by log-logistic models on the basis of visual estimates of crop injury, yield components (plants m⁻², ears plant⁻¹, kernels cob⁻¹ and 100-kernel weight) and grain yield. Popcorn response to flaming was influenced by the crop growth stage and propane dose. Based on various parameters evaluated, popcorn flamed at the 5-leaf showed the highest tolerance while the 2-leaf was the most susceptible stage. The maximum yield reductions were 45%, 9% and 16% for the 2-leaf, 5-leaf and 7-leaf stages, respectively. In addition, propane doses that resulted in a 5% yield loss were 23 kg ha⁻¹ for the 2-leaf and 7-leaf and 30 kg ha⁻¹ for the 5-leaf stage. Flaming has a potential to be used effectively in organic popcorn production if properly used.     

Timing and propane dose of broadcast flaming to control weed population influenced yield of sweet maize (Zea mays L. var. rugosa)

Farmers are interested to produce sweet maize under organic production systems and propane flaming could be a potential alternative tool for weed control in organic sweet maize production. Therefore, the objective of this study was to investigate the response of sweet maize to broadcast flaming as influenced by propane dose and crop growth stage. Field experiments were conducted at the Haskell Agricultural Laboratory of the University of Nebraska, Concord, NE in 2008 and 2009 using five propane doses applied at three different growth stages of V2 (2-leaf), V5 (5-leaf) and V7 (7-leaf). The propane doses were 0, 13, 24, 44 and 85 kg ha⁻¹. The response of sweet maize to propane flaming was evaluated in terms of visual crop injury, effects on plant height, yield components (plants m⁻², tillers plant⁻¹, number of ears plant⁻¹, cob length and number of seeds cob⁻¹) and fresh marketable yield. The response of different growth stages of sweet maize to propane doses was described by log-logistic models. Based on most parameters tested, V7 was the most tolerant while V2 was the least tolerant stage for broadcast flaming. The maximum yield reductions with the highest propane dose of 85 kg ha⁻¹ were 22%, 12% and 6% for V2, V5 and V7 stages, respectively. Furthermore, a 5% yield reduction was evident with 23, 25 and 36 kg ha⁻¹ of propane for V2, V5 and V7 growth stages, respectively, suggesting that plants flamed at V7 stage can tolerate higher dose of propane for the same yield reduction compared to the other growth stages. We believe that flaming has a potential to be used effectively in organic sweet maize production if properly used.     

Irrigated cotton in the tropical dry season. I: Yield,its components and crop development

Growing cotton during the dry (winter) season avoids many insect pests endemic in the wet season (summer) and could permit the reintroduction of cotton to the semi-arid tropics in Australia. This research addressed the questions: (1) what yield is possible given the lower mid-season radiation and temperature of the dry season, (2) the prediction and management of crop development using a range of sowing months to assess whether cotton can be grown and picked within the dry season. Over three seasons two Gossypium hirsutum L. (upland) cultivars and one Gossypium barbadense L. cultivar were sown from March, to June at the Ord River (15.5°S) in Western Australia. For the upland cultivars, lint yields of 1900–2300 kg/ha for March and April sowings were at the high end of Australian and International benchmarks. High lint yields were linearly correlated with a greater proportion of bolls that were located on outer sites on fruiting branches than for high yielding crops in temperate climates (∼30°lat.). The change in boll position increased the length of the growing season which was also linearly correlated with yield. Future research needs to confirm if low minimum temperatures early in flowering caused the change in boll position and to measure the impact of extreme temperature seasons on yield and time to maturity. The lint yield of the G. barbadense cultivar was highest at a March sowing, at least 87% of the upland cultivars, which is comparable with temperate climates. The frequency of temperatures >35 °C and <11 °C affected time to squaring, requiring modification of existing development models derived in temperate climates. It was concluded sowing during March to April should achieve the dual objectives of high yields and avoidance of rain at maturity. The wide temperature range observed in these experiments improved the prediction of boll period from mean temperature; this function should be applicable outside the semi-arid tropics.     

Interactions between crop biomass and development of foliar diseases in winter wheat and the potential to graduate the fungicide dose according to crop biomass

Foliar pathogens such as Zymoseptoria tritici and Puccinia striiformis causing septoria leaf blotch and yellow rust respectively can cause serious yield reduction in winter wheat production, and control of the diseases often requires several fungicide applications during the growing season. Control is typically carried out using a constant fungicide dose in the entire field although there may be large differences in crop development and biomass across the field. The objective of the study reported in this paper was to test whether the fungicide dose response curve controlling septoria leaf blotch and other foliar diseases in winter wheat was dependent on crop development and biomass level. If such a biomass dependent dose response was found it was further the purpose to evaluate the potential to optimize fungicide inputs in winter wheat crops applying a site-specific crop density dependent fungicide dose. The study was carried out investigating fungicide dose response controlling foliar diseases in winter wheat at three biomass densities obtained growing the crop at three nitrogen levels and using variable seed rates. Further the field experiments included three fungicide dose rates at each biomass level, an untreated control, and 75%, 50% and 33% of the recommended fungicide dose rate and the experiments were replicated for three years. Crop biomass had a significant influence on occurrence of septoria and yellow rust with greater disease severity at increasing crop biomass. In two of three years, the interaction of crop biomass and fungicide dose rate had a significant influence on disease severity indicating a biomass-dependent dose response. The interaction occurred in the two years with high yield potential in combination with severe disease attack. If the variation in crop density and biomass level obtained in the study is representative of the variation found cultivating winter wheat in heterogeneous fields, then there seems to be scope for optimizing fungicide input against foliar diseases site-specific adapting the dose according to crop density/biomass.     

High-yield irrigated maize in the Western U.S. Corn Belt: II. Irrigation management and crop water productivity

Appropriate benchmarks for water productivity (WP), defined here as the amount of grain yield produced per unit of water supply, are needed to help identify and diagnose inefficiencies in crop production and water management in irrigated systems. Such analysis is lacking for maize in the Western U.S. Corn Belt where irrigated production represents 58% of total maize output. The objective of this paper was to quantify WP and identify opportunities to increase it in irrigated maize systems of central Nebraska. In the present study, a benchmark for maize WP was (i) developed from relationships between simulated yield and seasonal water supply (stored soil water and sowing-to-maturity rainfall plus irrigation) documented in a previous study; (ii) validated against actual data from crops grown with good management over a wide range of environments and water supply regimes (n = 123); and (iii) used to evaluate WP of farmer's fields in central Nebraska using a 3-y database (2005–2007) that included field-specific values for yield and applied irrigation (n = 777). The database was also used to quantify applied irrigation, irrigation water-use efficiency (IWUE; amount of yield produced per unit of applied irrigation), and the impact of agronomic practices on both parameters. Opportunities to improve irrigation management were evaluated using a maize simulation model in combination with actual weather records and detailed data on soil properties and crop management collected from a subset of fields (n = 123). The linear function derived from the relationship between simulated grain yield and seasonal water supply, namely the mean WP function (slope = 19.3 kg ha⁻¹ mm⁻¹; x-intercept = 100 mm), proved to be a robust benchmark for maize WP when compared with actual yield and water supply data. Average farmer's WP in central Nebraska was ∼73% of the WP derived from the slope of the mean WP function. A substantial number of fields (55% of total) had water supply in excess of that required to achieve yield potential (900 mm). Pivot irrigation (instead of surface irrigation) and conservation tillage in fields under soybean–maize rotation had the greatest IWUE and yield. Applied irrigation was 41 and 20% less under pivot and conservation tillage than under surface irrigation and conventional tillage, respectively. Simulation analysis showed that up to 32% of the annual water volume allocated to irrigated maize in the region could be saved with little yield penalty, by switching current surface systems to pivot, improving irrigation schedules to be more synchronous with crop water requirements and, as a fine-tune option, adopting limited irrigation.     

Making sense of yield trade-offs in a crop sequence: A New Zealand case study

Crop growth is driven by the capture and utilisation of solar radiation. The most productive crop sequences are those that maximise the interception and use of solar radiation. However, there are yield trade-offs because of the timing of transitions between successive crops. A longer duration of one crop will mean that the following crop is sown later and will therefore produce a lower yield. Maximising the yield of a sequence involves a compromise between the yields of successive crops. We describe a case study of a forage cropping rotation in New Zealand, demonstrating how simulation models can be used to define the best compromise between the yields of successive crops, and thereby maximise the total yield of the full sequence.A case study using a series of long-term simulation experiments for four diverse environments in New Zealand was undertaken in a continuous, summer maize - winter cereal, cropping sequence. Maize sowing dates and hybrid durations, and cereal sowing and harvest times were varied systematically. The actual simulated crop and sequence yields varied from site to site, but there was a consistent trend identifying the most productive combinations of sowing date and hybrid duration. The sequence of comparatively late sowing date of maize (1 December) and a long-season hybrid maximised the total yield of the sequence. The highest sequence yields were achieved by balancing the need to capture a high level of annual solar radiation and the need to have a large proportion of solar radiation captured by maize, which has the greater RUE in summer. This analysis illustrates how crop simulation models can be used to design and understand the processes that give the most productive cropping sequences.     

Study of faba bean (Vicia faba L.) winter-hardiness and development of screening methods

In cool-temperate regions, faba bean (Vicia faba L.) is mainly grown as a spring crop despite the higher yield potential of the winter type, because of the insufficient winter-hardiness of the present winter genotypes. The objective of this study was to assess winter-hardiness and frost tolerance, to quantify the hardening effect on physiological traits, and to identify auxiliary traits for winter-hardiness. To do so, 31 representative entries were tested in controlled frost tests for frost tolerance and in 12 European environments for winter-hardiness. Total fatty acid composition, proline content, and electrolyte leakage of leaves were analysed. Across all environments, five European winter genotypes were identified with superior winter-hardiness. Controlled frost tests indicated that frost tolerance is a significant, but not an exhaustive component of winter-hardiness (0.021 < |r| < 0.737**). These tests revealed the high frost tolerance of several poorly winter-hardy experimental lines and the limited frost tolerance of well-known winter types. Fatty acid changes due to hardening, proline content, and electrolyte leakage were more strongly correlated with frost tolerance than with field-based winter-hardiness. Although frost tolerance, fatty acid composition, proline content, and electrolyte leakage were significantly correlated with winter-hardiness, the rather low correlation values do not allow a general use of one of them alone to indirectly select for winter-hardiness.     

Amaranth (Amaranthus hypochondriacus) as an alternative crop for sustainable food production: Phenolic acids and flavonoids with potential impact on its nutraceutical quality

The demand for food is increasing, not only to meet food security for growing populations, but also to provide more nutritious food, rich in good quality proteins and nutraceutical compounds. The amaranth (Amaranthus hypochondriacus) plant, in addition to its high nutritive and nutraceutical characteristics, has excellent agronomic features. The objective of the present study was to analyze some physical and proximal-nutritional properties of amaranth seeds obtained from different varieties grown in arid zones and characterize their phenolic acids and flavonoids. Two commercial (Tulyehualco and Nutrisol) and two new (DGETA and Gabriela) varieties of A. hypochondriacus were grown at the Mexican Highlands zone. Tulyehualco and DGETA varieties had higher seed yield of 1475 and 1422 kg ha⁻¹, respectively, comparable to corn and soybean production in agricultural areas. Gabriela had the highest protein content of 17.3%, but all varieties had an adequate balance of essential amino acids. Polyphenols as rutin (4.0–10.2 μg g⁻¹ flour) and nicotiflorin (7.2–4.8 μg g⁻¹ flour) were detected. Amaranth can be cultivated in arid zones where commercial crops cannot be grown; the seeds besides their well known nutritive characteristics could be a source of phenolic compounds of high antioxidant properties.     

Field evaluation of yield effects on the U.S.A. heirloom sweetpotato cultivars infected by Sweet potato leaf curl virus

The incidence of Sweet potato leaf curl virus (SPLCV), a Begomovirus, on sweetpotato, Ipomoea batatas (L.) Lam. (Convolvulaceae), in South Carolina, U.S.A. has increased rapidly in recent years. This is likely due to the use of infected propagating materials and the increasing population of its vector, the sweetpotato whitefly, Bemisia tabaci (Gennadius). In this study, we demonstrated in field experiments that SPLCV infection reduced the yields of most heirloom sweetpotato lines relative to the yields of non-infected plants. Real-time polymerase chain reaction (PCR) technology specific to several common sweetpotato viruses was used to determine the virus infection status in 69 selected accessions of heirloom sweetpotato lines. Meristem tip culture technology was used to regenerate virus-free plants from these materials. To ensure the virus-free status, each mericlone was evaluated using real-time PCR and graft bio-indexing on the indicator species, Ipomoea setosa Ker Gawl. Mericlones of 27 cultivars were found to be free of the viruses. The 27 cultivars were included in a field test to determine the effect of SPLCV infection on yield. Yields of virus-free plants of the cultivars ranged from 10 to 80% greater than the yields of SPLCV-infected plants. However, the yield differences between virus-free and infected plants were diminished in the second year of the field experiment due to a rapid re-infection by SPLCV. These results demonstrate the importance of using certified, virus-tested seed roots or cuttings. The rapid re-infection of the virus-tested sweetpotato plants with SPLCV observed in these studies suggests that management of the whitefly population should be a critical element in control of this important virus.     

High level of resistance to Sclerotinia sclerotiorum in introgression lines derived from hybridization between wild crucifers and the crop Brassica species B. napus and B. juncea

Sclerotinia rot caused by the fungus Sclerotinia sclerotiorum is one of the most serious and damaging diseases of oilseed rape and there is keen worldwide interest to identify Brassica genotypes with resistance to this pathogen. Complete resistance against this pathogen has not been reported in the field, with only partial resistance being observed in some Brassica genotypes. Introgression lines were developed following hybridization of three wild crucifers (viz. Erucastrum cardaminoides, Diplotaxis tenuisiliqua and E. abyssinicum) with B. napus or B. juncea. Their resistance responses were characterized by using a stem inoculation test. Seed of 54 lines of B. napus and B. juncea obtained from Australia, India and China through an Australian Centre for International Agricultural Research (ACIAR) collaboration programme were used as susceptible check comparisons. Introgression lines derived from E. cardaminoides, D. tenuisiliqua and E. abyssinicum had much higher levels (P < 0.001) of resistance compared with the ACIAR germplasm. Median values of stem lesion length of introgression lines derived from the wild species were 1.2, 1.7 and 2.0 cm, respectively, as compared with the ACIAR germplasm where the median value for stem lesion length was 8.7 cm. This is the first report of high levels of resistance against S. sclerotiorum in introgression lines derived from E. cardaminoides, D. tenuisiliqua and E. abyssinicum. The novel sources of resistance identified in this study are a highly valuable resource that can be used in oilseed Brassica breeding programmes to enhance resistance in future B. napus and B. juncea cultivars against Sclerotinia stem rot.     

Efficacy of composting infected plant residues in reducing the viability of Pepper mild mottle virus, Melon necrotic spot virus and its vector,the soil-borne fungus Olpidium bornovanus

Survival of Pepper mild mottle virus (PMMV) and Melon necrotic spot virus (MNSV) in diseased plant residues of pepper and melon, respectively, was studied in several experiments investigating drying and composting conducted in experimental heaps. The viability of the soil-borne fungus Olpidium bornovanus, the vector of MNSV, in infected melon root residues was also evaluated. Maximum temperatures in the heap reached 61.9–73.8 °C during composting processes. Drying of plant residues reduced the infectivity of MNSV whereas the infectivity of PMMV and O. bornovanus was unaffected by drying. Neither the virus nor the fungus was viable after composting. PMMV antigens where detected by serology after 30 and 60 days composting in the four experiments, but virus infectivity was detected only in one process after 30 days. Our results show that the use of composts using plant residues from PMMV and MNSV-infected crops as organic amendments in SE Spain do not appear to pose a risk of re-introducing pathogens to soil. Environmental conditions in that area are suitable for the adequate elimination of these pathogens from infected vegetable residues through composting even during winter.     

Exogenous Antioxidants Improve the Accumulation of Saturated and Polyunsaturated Fatty Acids in Schizochytrium sp. PKU#Mn4

Species of Schizochytrium are well known for their remarkable ability to produce lipids intracellularly. However, during their lipid accumulation, reactive oxygen species (ROS) are generated inevitably as byproducts, which if in excess results in lipid peroxidation. To alleviate such ROS-induced damage, seven different natural antioxidants (ascorbic acid, α-tocopherol, tea extract, melatonin, mannitol, sesamol, and butylated hydroxytoluene) were evaluated for their effects on the lipid accumulation in Schizochytrium sp. PKU#Mn4 using a fractional factorial design. Among the tested antioxidants, mannitol showed the best increment (44.98%) in total fatty acids concentration. However, the interaction effects of mannitol (1 g/L) and ascorbic acid (1 g/L) resulted in 2.26 ± 0.27 g/L and 1.45 ± 0.04 g/L of saturated and polyunsaturated fatty acids (SFA and PUFA), respectively, in batch fermentation. These concentrations were further increased to 7.68 ± 0.37 g/L (SFA) and 5.86 ± 0.03 g/L (PUFA) through fed-batch fermentation. Notably, the interaction effects yielded 103.7% and 49.6% increment in SFA and PUFA concentrations in batch fermentation. The possible mechanisms underlining those increments were an increased maximum growth rate of strain PKU#Mn4, alleviated ROS level, and the differential expression of lipid biosynthetic genes andupregulated catalase gene. This study provides an applicable strategy for improving the accumulation of SFA and PUFA in thraustochytrids by exogenous antioxidants and the underlying mechanisms.     

Effects of the application rate and time of the growth regulator trinexapac-ethyl in seed crops of Lolium perenne L. in relation to spring nitrogen rate

To test the effects of the growth regulator trinexapac-ethyl (Moddus 250 EC) in the main seed crop of grasses in the Netherlands, 10 field trials were conducted in perennial ryegrass (Lolium perenne L.). These field trials were carried out in first and second seed harvest crops during 1999–2002. Four rates of Moddus (untreated, 0.4, 0.8 and 1.6 L product ha⁻¹) were applied at the start of stem elongation (DC 30–31, zero to one node) during the first two years. In addition, the effect of timing of the application of 0.8 L Moddus ha⁻¹ was studied (untreated, DC30–31, DC31–33, DC33–37). In most trials, in addition to the normal amount, 45 kg N ha⁻¹ extra spring nitrogen was applied. The work reported is valuable, and has relevance to all areas of the globe where this perennial ryegrass is grown for seed, e.g., northern Europe, the US (particularly, Oregon), New Zealand, Australia, Chile and Argentina.     

借鉴美国经验科学发展我国的玉米产业

在分析了美国玉米生产的现状和先进经验的基础上,根据我国玉米产业现状,提出了加强优质、专用、抗逆和资源高效利用型玉米新品种的培育与推广;促进节本增效、规范化技术的研制和配套栽培技术的应用,尽可能降低生产成本;逐步建立健全优质、专用玉米标准化生产基地和产业化体系;加强技术培训,培育高素质的产业化生产劳动力;开展玉米产品安全性研究等发展方向或措施,为政府和农业主管部门的宏观决策提供依据。     

New insights into high-molecular-weight glutenin subunits and sub-genomes of the perennial crop Thinopyrum intermedium (Triticeae)

Intermediate wheatgrass (Thinopyrum intermedium) is a perennial crop that possesses desirable agronomic traits and provides environmental services, e.g., reducing soil erosion, nitrate leaching and inputs of energy and pesticide. Thus, intermediate wheatgrass is currently being domesticated as a perennial grain crop. However, the genetic information for molecular breeding is quite limited. Here we report a molecular analysis of high-molecular-weight glutenin subunits (HMW-GS) in intermediate wheatgrass using gene cloning and protein biochemistry. Five HMW-GS genes were isolated from individual intermediate wheatgrass plants: two x-type genes TiHGS1 and TiHGS4, and three y-type genes TiHGS2, TiHGS3 and TiHGS5. Among them, TiHGS5 was novel and possessed an additional cysteine residue at the N-terminal domain or repetitive domain. Sequence alignments showed that TiHGS1 and TiHGS2 genes shared high identities (>96%) with the Glu-1Dx and Glu-1Dy genes, respectively, in common wheat and Aegilops species, TiHGS3 with HMW-GS genes from Dasypyrum or Pseudoroegneria, and TiHGS4 and TiHGS5 with HMW-GS genes from Thinopyrum elongatum. This work provides substantial new insights into the gene compositions and protein profiles of HMW-GS in intermediate wheatgrass, and also gives evidence about the genome components of intermediate wheatgrass.