Growth and abortion of flower buds in gynoecious cucumber plants in relation to temperature

The growth of flower buds in a gynoecious cucumber cultivar was studied at 15, 21 and 27°C. Competition between buds in the same node was measured as the ratio of the growth rates of individual buds. This competition was stronger at 21 and 27 than at 15°C. At 15°C, at least 3 buds were about equally strong; at 21°C, 2 buds developed fast and suppressed the other buds; at 27°C, the first bud which developed suppressed all other buds. When plants were transferred from one temperature to another, the growth-rate ratio between buds in older nodes was maintained. In nodes formed in the new temperature regime, the growth-rate ratio was determined by the new temperature.     

A comparison of morphology,pathogenicity and restriction fragment patterns of mitochondrial DNA among isolates of Phytophthora porri Foister

Thirteen strains ofPhytophthora porri from five different hosts were compared with respect to their morphology, cardinal temperatures for growth, pathogenicity to leek and cabbage and restriction fragment patterns of mitochondrial DNA. Morphology of vegetative growth was rather similar in most isolates. Those characters which differed among isolates showed overlapping variability and could not be used to distinguish groups, with the exception of production of oogonia and sporangia and the antheridium type. Considerable differences were found in restriction patterns of mitochondrial DNA, isolates from the same host mostly showing identical patterns. Isolates from differentAllium species showed relatively similar restriction patterns if compared to the other isolates. Isolates fromBrassica oleracea proved to be a homogeneous group, quite different from the others with respect to restriction patterns, production of sporangia, production of oogonia, antheridium type and pathogenicity. One isolate, CBS 366.59, isolated from and pathogenic toA. porrum, deviated in many characters from the other isolates. It showed the restriction patterns ofPhytophthora nicotianae and also the high cardinal temperatures for growth typical for this species. The sporangia, however, were distinctly non-papillate and the majority of antheridia was of the paragynous type.     

Genetic Engineering in Pea Crop Improvement

Abstract

Genetic engineering can be used to complement traditional breeding programmes in those plant species where suitable tissue culture and transformation methods allowing regeneration of fertile transgenic plants have been developed. Pea, an important legume crop, was earlier considered to be recalcitrant to genetic engineering. Recent advances in tissue culture methods have, however, made it possible to obtain fertile transgenic pea plants. This paper summarizes the results obtained in developing transformation methods for pea.     

Leaf photosynthetic characteristics of silver birch during three years of exposure to elevated concentrations of CO2 and O3 in the field

Effects of elevated concentrations of carbon dioxide ([CO2]) and ozone ([O3]) on photosynthesis and related biochemistry of two European silver birch (Betula pendula Roth) clones were studied under field conditions during 1999-2001. Seven-year-old trees of Clones 4 and 80 were exposed for 3 years to the following treatments in an open-top chamber experiment: outside control (OC), chamber control (CC), 2x ambient [CO2] (EC), 2x ambient [O3] (EO) and 2x ambient [CO2] + 2x ambient [O3] (EC+EO). During the experiment, gas exchange, chlorophyll fluorescence, amount and activity of Rubisco, concentrations of chlorophyll, soluble protein, soluble sugars, starch, nitrogen (N) and carbon:nitrogen (C:N) ratio were determined in short- and long-shoot leaves. Elevated [CO2] increased photosynthetic rate by around 30% when measurements were made at the growth [CO2]. When measured at ambient [CO2], photosynthesis was around 15% lower in EC trees than in CC trees. This was related to a approximately 10% decrease in total leaf N, to 26 and 20% decreases in the amount and activity of Rubisco, respectively, and to a 49% increase in starch concentration in elevated [CO2]. Elevated [O3] had no significant effect on gas exchange parameters and its effect on biochemistry was small in both clones. However, elevated [O3] decreased the proportion of Rubisco in total soluble proteins and the apparent quantum yield of photosystem II (PSII) photochemistry in light and increased non-photochemical quenching in 2000. The interactive effect of CO2 and O3 was variable. Elevated [O3] decreased chlorophyll concentration only in EO trees, and the EC+EO treatment decreased the total activity of Rubisco and increased the C:N ratio more than the EO treatment alone. The small effect of elevated [O3] on photosynthesis indicates that these young silver birches were fairly tolerant to annual [O3] exposures that were 2-3 times higher than the AOT40 value of 10 ppm.h. set as a critical dose for forest trees.     

Are field populations of arbuscular mycorrhizal fungi able to suppress the transmission of seed-borne <Emphasis Type="Italic">Bipolaris sorokiniana</Emphasis> to aerial plant parts?

The development of seed-borne Bipolaris sorokiniana in barley in the presence of arbuscular mycorrhizal fungi was studied. To exploit natural variation in their ability to control disease development, arbuscular mycorrhizal fungi from various Swedish arable soils were multiplied in trap cultures using a mixture of plant species. Six out of eight trap culture soil inocula were able to reduce transmission of B. sorokiniana from seeds to stem bases when grown together with infected barley seed. Based on this result two soil inocula, of different origin, from semi-natural grassland and barley respectively, were chosen for further greenhouse studies. Both soil inocula gave significant reductions in pathogen transmission from seeds to seedlings compared to the untreated control. In addition, treatment with spore inocula, collected from the different trap culture soils, showed disease suppression. Treatment with spores from the pure culture Glomus intraradices gave significant reduction in leaf lesion development. A treatment with the commercial inoculum Vaminoc^® was included and gave some suppression of the pathogen. In conclusion this study has shown that AM soil inocula from trap cultures suppressed the transmission of seed-borne B. sorokiniana in the aerial parts of barley plants.     

Association between costly veterinary-care events and 5-year survival of Swedish insured warmblooded riding horses

Our objective was to estimate the 5-year survival to death in insured warmblooded riding horses (as reflected by a life-insurance claim) in horses with or without at least one costly veterinary-care event (VCE) in 1997. We also determined the impacts of gender, age, previous diagnosis of veterinary claim, geographic variables, cost for veterinary claims and life-insurance value upon the survival. The design was a retrospective cohort study using a population of warmblooded riding horses insured in a Swedish animal-insurance company (Agria Insurance, P.O. 70306, SE-107 23 Stockholm, Sweden) in 1997. All horses in this population had insurance both for veterinary-care and life ("complete" insurance reimbursing the insurance holder for most medical problems). We followed two cohorts (2,495 horses with > or = 1 VCE and 15,576 horses with no VCE in year 1997). The median VCE cost in horses with > or =1 VCE was 3,800 SEK, with 10th and 90th percentiles of 1,400 and 11,400 SEK respectively. In total 944 of the 2,495 horses (38%) in the VCE-positive cohort and 2,962 of the 15,576 horses (19%) in the VCE-negative cohort had died (had a settled life-insurance claim) after the follow-up time. An exponential-regression model showed that geldings had a higher risk of claimed death compared to mares and mares had a higher risk compared to stallions. The risk of death increased linearly with age. The risk of death increased with increasing life-insurance value. Horses with previous lameness had the lowest survival, and for high-cost claims this increased risk was not associated with age.