Conservation of Arabidopsis thaliana photoperiodic flowering time genes in onion (Allium cepa L.)

The genetics underlying onion development is poorly understood. Here the characterisation of onion homologues of Arabidopsis photoperiodic flowering pathway genes is reported with the end goal of accelerating onion breeding programmes by understanding the genetic basis of adaptation to different latitudes. The expression of onion GI, FKF1 and ZTL homologues under SD and LD conditions was examined using quantitative RT-PCR. The expression of AcGI and AcFKF1 was examined in onion varieties which exhibit different daylength responses. Phylogenetic trees were constructed to confirm the identity of the homologues. AcGI and AcFKF1 showed diurnal expression patterns similar to their Arabidopsis counterparts while AcZTL was found to be constitutively expressed. AcGI showed similar expression patterns in varieties which exhibit different daylength responses whereas AcFKF1 showed differences. It is proposed that these differences could contribute to the different daylength responses in these varieties. Phylogenetic analyses showed that all the genes isolated are very closely related to their proposed homologues. The results presented here show that key genes controlling photoperiodic flowering in Arabidopsis are conserved in onion and a role for these genes in the photoperiodic control of bulb initiation is predicted. This theory is supported by expression and phylogenetic data

Seed production studies in Ruzi grass (Brachiaria ruziziensis Germain and Everard) : a thesis presented in partial fulfilment of the requirement for the degree of Master of Agricultural Science in Seed Technology, at Massey University, Palmerston North, New Zealand

The effect of photoperiod on seed production in Ruzi grass (Brachiaria ruziziensis) was investigated in order to gain a better understanding of reproductive behaviour. The experiment was conducted in a controlled temperature glasshouse which provided day and night temperatures of 25°C±5. Plants were raised from seed obtained from Thailand. During the early stage of growth (10 days after germination) Ruzi grass plants were exposed to controlled photoperiods of 14, 13, 12 or 11 hours for a period of 30 days followed by exposure to the decreasing natural daylength occurring in the New Zealand autumn. The results of this experiment showed there was no "trigger" daylength requirement for reproductive initiation, since Ruzi grass was able to produce flowers in all daylength treatments (14, 13, 12 and 11 h). However, the data did show that the shorter the daylength, the greater the seed yield (i.e. potential seed yield was greatest at 11 h). Accordingly, the results confirm the conclusion of Dirven et al., (1979), that Ruzi grass is a quantitative short-day plant. The results of this study appear to contradict the reproductive behaviour of Ruzi grass in Thailand, where a critical daylength of approximately 12½ h to trigger reproductive development seems necessary. These results suggest that it is theoretically possible for Ruzi grass to produce seed over the entire range of daylengths which occur in Thailand, as recorded in this experiment. The fact that this does not occur is possibly due to a juvenility problem, as the plants are only 4-6 weeks old after the onset of the rainy season in late April/early May when the daylength is approximately 13 h, and due to drought conditions which occur in December under the shortest daylength of approximately 11½ h. However, this needs to be confirmed, possibly by conducting trials in Thailand under an 11½ h daylength with irrigation to overcome lack of water. Daylength strongly affected inflorescence numbers and inflorescence components. As daylength declined the number of racemes/inflorescence arising from basal tillers tended to decrease. This was accompanied by a corresponding increase in aerial tiller numbers. Floret number/raceme was a more important factor influencing seed yield than raceme number/inflorescence. Basal reproductive and vegetative tiller numbers were not significantly affected by daylength, although aerial reproductive tillers did increase as daylength declined. Total tiller numbers were low, even although they continued to show a steady increase through to harvest, when approximately 30% were reproductive and 70% vegetative. Ruzi grass produced more inflorescences from aerial tillers than from basal tillers. The morphological changes occurring during the changeover from vegetative to reproductive development were divided into five stages. The time required from early raceme initiation in the "double ridge' stage to inflorescence exsertion was 22 days. It appears that Ruzi grass does not have a characteristically prolonged anthesis within an individual inflorescence, as all anthers were exserted within 1-2 weeks. Despite this, approximately 80% of florets within an inflorescence completed anthesis in 7 days. Within individual inflorescences, anthesis began in the middle region of the uppermost raceme and subsequently extended to the upper and lower raceme(s). Ruzi grass exhibited a prolonged head emergence period of about 3 months which was highly variable both within and between individual plants. Seed development studies suggested that although some variation in the extent and timing of seed shedding may occur between plants, harvesting should not be carried out before 20-25 days after anthesis (maximum viability), and should not be delayed longer than 30 days after anthesis (maximum dry weight)

Workshop and desk study to appraise technical difficulties associated with organic pullet rearing

Background To date, Regulation (EC) 1804/1999 and UKROFS Standards allow conventionally reared pullets up to 18 weeks of age to be brought into systems of organic egg production. Pullets must be reared according to the rules laid down in Regulation (EC) 1804/1999 and according to UKROFS Standards for at least six weeks, before the eggs may be sold as organic eggs. The derogation for pullet rearing has been agreed for a transitional period expiring on 31 December 2003. If pullets are to be reared from day old in an organic system in accordance with Regulation (EC) 1804/1999 and UKROFS Standards this may potentially create a number of technical problems, which may disadvantage UK producers considering organic egg production. A series of workshops and a literature review were commissioned by MAFF to provide possible solutions to these technical problems. Objectives 1. To organise a workshop involving key members of the egg sector of the poultry industry, representatives of organic sector bodies and of MAFF to consider technical problems that may occur when rearing pullets organically, and to identify possible solutions. 2. To address some of the perceived technical problems by reviewing the available literature on conventional pullet rearing and assessing the extent to which published results can be applied to organic systems. 3. To reconvene workshop members to discuss findings from the literature review, to identify research priorities and to consider mechanisms for technology transfer. Methodology There were three separate but related stages to the project. Stage one comprised a workshop involving representatives of the egg sector of the poultry industry, of the Soil Association, of ADAS and of MAFF, and attendees were specifically invited to comment on the likely difficulties that might be experienced when attempting to rear pullets in an organic production system. Stage two was a desk study in the form of a literature review. Literature searches of the major international abstracting databases were done using key words related to the technical problems highlighted by workshop one attendees. Stage three was a second workshop where attendees discussed the findings from the literature, identified research priorities and considered mechanisms for technology transfer. Results The outcome of workshop one was that several likely difficulties associated with rearing pullets in an organic production system were identified and these included; 1) the application of light programmes in pullets receiving natural light when the maximum daily light period is 16 hours; 2) nutrition; 3) housing and pasture management, and; 4) food safety risks. Implications of findings, future work and policy relevance The implications of the findings are that with current scientific information there will be technical difficulties associated with rearing pullets in an organic system. The most important technical difficulties are to do with photoperiodism, nutrition, pasture management and rotation, and methods of controlling injurious feather pecking. Also a maximum permissible daylength of 16 hours for rearing organic pullets would mean that producers in Northern European countries may be disadvantaged. The project addressed MAFF’s policy of supporting the development of organic livestock production within the UK. The project has provided information to MAFF and the egg sector of the poultry industry about the key technical problems associated with organic pullet rearing, possible solutions to these problems and, where scientific information is missing, future research needs have been identified

Why does low intensity, long-day lighting promote growth in Petunia, Impatiens, and tomato?

Numerous reports demonstrate that low intensity, long-day (LD) lighting treatments can promote growth. However, there are conflicting suggestions as to the mechanisms involved. This study examines the responses of Petunia, Impatiens, and tomato to LD lighting treatments and concludes that no single mechanism can explain the growth promotion observed in each case. Petunia showed the most dramatic response to photoperiod; up to a doubling in dry weight (DW) as a result of increasing daylength from 8 h d–1 to 16 h d–1.This could be explained by an increase in specific leaf area (SLA) comparable to that seen with shading. At low photosynthetic photon flux densities (PPFD), the increased leaf area more than compensated for any loss in photosynthetic capacity per unit leaf area. In Petunia, the response may, in part, have also been due to changes in growth habit. Impatiens and tomato showed less dramatic increases in DW as a result of LD lighting, but no consistent effects on SLA or growth habit were observed. In tomato, increased growth was accompanied by increased chlorophyll content, but this had no significant effect on photosynthesis. In both species, increased growth may have been due to a direct effect of LD lighting on photosynthesis. This is contrary to the generally held view that light of approx. 3 – 4 μmol m–2 s–1 is unlikely to have any significant impact on net photosynthesis. Nevertheless, we show that the relationship between PPFD and net photosynthesis is non-linear at low light levels, and therefore low intensity LD lighting can offset respiration very efficiently. Furthermore, a small increase in photosynthesis will have a greater impact when ambient light levels are low

Controlled environment life support system: Growth studies with potatoes

Results of experiments conducted to maximize the productivity of potatoes grown under controlled environmental conditions are discussed. A variety of parameters is examined which affect potato growth, specifically, photoperiod, light intensity, temperature, nitrogen nutrition, carbon dioxide concentration and culture techniques. These experiments were conducted using five different cultivars, Russet Burbank, Norchip, Superior, Kennebec and Norland. To achieve high productivity, three specific objectives were explored: (1) to develop effective cultural procedures, (2) to determine the most effective photoperiod and (3) to develop a mist culture system. It is felt that the productivity obtained in this study is below the maximum that can be obtained. High irradiance levels coupled with tuber-promoting conditions such as cooler temperatures, increased CO2 levels and lowered nitrogen concentrations should allow increases in tuber production. Tuberization appears to be accelerated by short daylengths although final yields are not increased. Mist culture techniques have not yet produced fully developed tubers. The use of supporting media and alteration of the nitrogen content of the mist solution are being explored as a way to allow tubers to develop to maturity

INTRA- AND INTER-STATE TRANSFERABILITY OF SOYBEAN VARIETY RESEARCH

An example of agricultural researching technology transfer and implications for the fiscal coordination and conduct of agricultural research programs is presented. Uniform Soybean Tests conducted in four Southern States are used to estimate the potential for transferability of soybean variety research among homogeneous sub-areas. The results indicate a high degree of transferability among the sub-areas. Coordinated management of soybean variety research could potentially provide more effective expenditure of soybean breeding research investments. Additionally, the concept or research transferability is not limited to soybeans or soybean variety research. Increased coordination of agricultural research investments by individual states may enhance existing benefits.Research and Development/Tech Change/Emerging Technologies,

Plant responses to photoperiod

Photoperiod controls many developmental responses in animals, plants and even fungi. The response to photoperiod has evolved because daylength is a reliable indicator of the time of year, enabling developmental events to be scheduled to coincide with particular environmental conditions. Much progress has been made towards understanding the molecular mechanisms involved in the response to photoperiod in plants. These mechanisms include the detection of the light signal in the leaves, the entrainment of circadian rhythms, and the production of a mobile signal which is transmitted throughout the plant. Flowering, tuberization and bud set are just a few of the many different responses in plants that are under photoperiodic control. Comparison of what is known of the molecular mechanisms controlling these responses shows that, whilst common components exist, significant differences in the regulatory mechanisms have evolved between these responses

Shortening day length as a previously unrecognized selective pressure for early breeding in a bird with long parental care

Several different selective pressures have been suggested to explain an intense competition for early return to breeding grounds in birds. In this study we hypothesized that shortening day length during summer months may constitute additional selective force acting towards early breeding in avian species with long parental care. To test this hypothesis, we studied time budget and foraging activities of early-nesting and late-nesting white storks Ciconia ciconia from the Central-European population. We found that duration and distance of foraging trips increased significantly over the course of the reproductive season. The relative frequency of foraging trips increased at the expense of other activities, such as resting, plumage maintenance, and nest maintenance. Mean daily foraging duration increased with increasing day length in the early part of the season, with 0.68 h of foraging per individual per 13.16 h of day length in mid-April increasing to 7.42 h of foraging per individual during solstice (16.61 h of day length). Afterwards, mean foraging duration continued increasing in spite of decreasing day length, reaching 11.63 h of foraging per individual per 14.92 h of day length at the end of the season in mid-August, when storks were forced to continue foraging after sunset in order to meet energy requirements of fledglings. The results suggest that shortening day length during summer months may constitute a serious time constraint on food delivery rates to offspring for late-breeding pairs of white storkEuropean Social Fund and the Polish National Budget in the D-RIM project of the Human Capital Programm