Range Of Crop Species Research Articles

Efficiency of reduced primer selectivity and bulked DNA analysis for the rapid detection of AFLP† polymorphisms in a range of crop species

Two approaches to optimise AFLP fingerprinting forthe rapid detection of genetic polymorphisms, i.e.reduced primer selectivity and bulked DNA analysiswere examined. The efficiency of reduced primerselectivity to increase the detection frequency ofgenetic polymorphisms and to obtain more informativefingerprinting profiles was tested in six differentcrops. The number of selective nucleotides was reducedto six in onion, to five in barley, potato, lettuceand cabbage, and to four in flax. This allowed therapid identification of several primer pairs that wereable to discriminate between closely relatedgermplasm. Reproducibility tests on replicate DNAsamples indicated no major negative effects on thereliability of the fingerprinting profiles due to theuse of less selective primers, although for onionpurified DNA was needed to avoid irreproducibleresults. In barley, flax and onion, a less thanfourfold increase in the number of fragments wasobserved when primer pairs were reduced by oneselective nucleotide. This result was attributed todifferent tolerance levels for amplificationmismatches between primer pairs of differentselectivity.The efficiency of bulked DNA analysis to detectgenetic polymorphisms was investigated in differentmixtures of two barley DNA samples. AFLP's of varyingintensity could still be recovered when the two DNA'swere mixed in a 1:1 ratio. However, the frequency ofrecovered bands quickly dropped when in the mixturesthe presence of the DNA carrying the fragments wasdecreased below 50%.The usefulness of the two approaches is discussed inrelation to various aspects of genetic resourcesmanagement.

Effect of temperature, seeding date, fungicide seed treatment and inoculation with Fusarium avenaceum on seedling survival, root rot severity and yield of lentil

Early seeding of lentil is necessary on the northern prairies to ensure that the crop has time to mature. However, planting into cold soils in spring results in slow germination, which may predispose seedlings to infection by soil-borne pathogens. In a controlled-environment study of the impact of temperature on infection of lentil seedlings (cv. Eston) byFusarium avenaceum, root rot symptoms were most severe at warm temperatures (20° to 27.5 °C) and declined in warmer or cooler soils. Field plots were seeded on three dates, which were spaced about 2 wk apart between early May and early June in four station years. Seedling emergence was most consistent and seed yield was highest in three of four sites at the second seeding date. Emergence and yield were substantially lower for the latest seeding date. Inoculation with F. avenaceum reduced establishment and seed yield. Seed treatment with Crown (thiabendazole and carbathiin) improved seedling survival, reduced root rot severity and increased seed yield relative to the inoculated control. Vitaflo-280 (thiram and carbathiin) also improved establishment and yield, but the effect was not as strong or consistent. Treatment with Raxil (tebuconazole) and Apron (metalaxyl) had no effect. The pathogenicity of aggressive isolates of F. avenaceum from lentil on a range of crop species was evaluated. All crops were susceptible to some degree, which indicates that the pathogen, once established, is likely to persist in a field for some time. This study demonstrated that early planting was required for maximum yield, that certain isolates of F. avenaceum were pathogenic on a wide range of hosts, and that seed treatment can be used to minimize losses from seedling blight and root rot in lentil. Key words: Lentil (Lens culinaris Medikus), Fusarium avenaceum, root rot, seeding date, thiabendazole, carbathiin, thiram, tebuconazole

An international cooperative programme indicates the widespread occurrence of ozone injury on crops

The UN/ECE ICP-Vegetation 1 United Nations Economic Commission for Europe International Cooperative Programme on effects of air pollution and other stresses on crops and non-wood plants (formerly ICP-Crops). 1 routinely investigates the effects of ambient ozone pollution on crops throughout Europe. Each year, a series of co-ordinated ambient air experiments are conducted over a large area of Europe and a range of crop species are observed for the occurrence of injury following ozone episodes. In 1995 and 1996, ozone injury was observed at sites throughout Europe from United Kingdom (Nottingham) to the Russian Federation (Moscow) and from Sweden (Östad) to Italy (Naples). The only site participating in the ICP-Vegetation where it was not observed was that at Finland (Jokioinen). Injury was identified on subterranean and white clover, French bean, soybean, tomato, and watermelon at one or more sites. Injury was also detected in gardens and on crops growing in commercial fields. Two short-term critical levels which incorporate ozone dose and air saturation vapour pressure deficit (VPD) were derived from the 1995 data. These were (i) an AOT40 2 The sum of the difference between the hourly concentration (ppb) and 40ppb when the concentration exceeds 40ppb for the hours when global radiation (GR) exceeds 50Wm −2. 2 of 200 ppb.h over 5 days when mean VPD (0930–1630 h) is below 1.5 kPa and (ii) an AOT40 of 500 ppb.h over 5 days when mean VPD (0930–1630 h) is above 1.5 kPa. In general, the 1996 data supported these critical levels although injury did occur on two occasions when the AOT40 was less than 50 ppb.h, and the VPD was less than 0.6 kPa. Thus, ICP-Vegetation experiments have shown that ozone injury can occur over much of Europe and that plants are most at risk in conditions of high atmospheric humidity.

Haploid Plants from Tissue Culture: New Plant Varieties in a Shortened Time Frame

Specialized plant tissue culture methods have enabled the production of completely homozygous breeding lines from gametic cells in a shortened time frame compared to conventional plant breeding. Plants from gametic cells of an F1 hybrid represent a gametic array each having a different genetic contribution from the parents. Lines exhibiting the desired characteristics are chosen for large-scale field trials as a prelude to commercialization. Although the number of new plant varieties developed via this method has been limited, refinement of tissue culture techniques has extended the range of crop species from which haploid plants have been produced as well as the efficiency resulting in large-scale haploid plant production. Several varieties developed via this method are grown on considerable acreage while others are being tested as candidates to replace varieties developed by conventional methods.

Protoplasts from Root Hairs of Crop Plants

It has been found possible to achieve rapid enzymatic degradation of the cell wall of the apices of root hairs from a wide range of crop species. Thereby it is possible to expose plasma membranes with partial protoplast release whilst maintaining the functional integrity of the plant. This exposure of plasma membranes provides a port of entry into the plant for a wide range of investigations including genetic manipulations.