Validation of the specificity and sensitivity of species-specific primers that provide a reliable molecular diagnostic for <Emphasis Type="Italic">Xiphinema diversicaudatum</Emphasis>, <Emphasis Type="Italic">X. index</Emphasis> and <Emphasis Type="Italic">X. vuittenezi</Emphasis>

Xiphinema diversicaudatum and X. index are vector nematode species of economic importance in viticulture regions as they can transmit Arabis Mosaic, Grapevine Fanleaf and Strawberry Latent Ringspot viruses to grapevine. Wang et al. (2003) designed species-specific diagnostic primers from ribosomal genes for both these vector species as well as a vector and a non-vector species X. italiae and X. vuittenezi, respectively. Our study aimed to confirm the specificity and determine the sensitivity and reliability of the primers for the two vector species, X. diversicaudatumand X. indexwhen challenged with closely related longidorid species and general nematode communities typical of vineyard soil. With one exception, no PCR product was observed when the primers were tested against six Longidorus, one Paralongidorus and one Xiphinema non-target species. Occasionally (three out of eight replicate PCR reactions) a weak PCR product was noted when primers for X. index were tested with L. elongatus. Furthermore, when challenged with a range of non-target nematode species comprising the nematode community typical of viticulture soil, no PCR product was amplified. An experimental dilution series of extracted DNA rigorously demonstrated that DNA from an equivalent single specimen of the target virus-vector species, X. diversicaudatum and/or X. index, could be detected amongst 1000 equivalent non-targetX. vuittenezi. Also, extracted DNA from an equivalent single target specimen was detected when added to DNA extracted from the overall soil nematode community. The primers were assessed further by using serial mixtures of actual nematodes rather than extracted DNA to simulate field soil. Using this method, a single target nematode could be detected amongst 200 non-target specimens. Given their specificity, sensitivity and reliability, it appears that these diagnostic primers will be of great benefit to phytosanitary/quarantine services related to the viticulture industry.     

In vitro and in vivo production of cell wall degrading enzymes by Botrytis cinerea from tomato

The production and activity of pectolytic and cellulolytic enzymes byBotrytis cinerea in tomato plants, as well as by conidia of this fungus in some nutrient media was studied. In inoculated tomato plants, the activity of these enzymes varied. PME, endo-PG and exo-PG were produced in petioles and fruits, while cellulase was only found in those parts which were softened by the invading mycelium. PGTE could only be detected in the softened parts of the petiole stumps. In suitble substrates, PME, endo-PG and exo-PG are produced rapidly with the onset of germination of the conidia. At some temperatures, endo-PG activity was found before germination could be observed. Some endo- and exo-PG was detected in washing water of conidia. The significance of the production of these enzymes by germinating conidia in relation to the infection process on tomato plants is discussed.Samenvatting In geïnoculeerde delen van een tomateplant blijkt de activiteit van deze enzymen afhankelijk te zijn van de aard van het aangetaste weefsel en de mate van aantasting (Tabel 1). Conidiën blijken in bepaalde media zeer snel pectolytische enzymen te vormen (Tabel 2, Fig. 1). Endo-PG activiteit kon bij 26° en 30°C in een natriumpolypectaatmedium worden gemeten voordat kieming van de conidiën kon worden aangetoond, zij het in zeer geringe hoeveelheid, lijkt aanwezigheid van deze twee enzymen in niet gekiemde conidiën aannemelijk. PME blijkt in een pectinebevattend medium te kunnen worden aangetoond op het moment, waarop kiembuizen zichtbaar worden. Cellulase kon daarentegen in een medium met kiemende sporen niet worden gevonden.     

A critical path analysis of fruit production in strawberry

The method of Critical Path Analysis has been applied to strawberry fruit production from runner propagation to first harvest in an experimental situation. The quantitative components of yield and the stages of their creation have been identified and arranged in sequential order.Analysis of crop data showed that large variations in yield potential arose early in development, from causes not identified in the experiment. In the fruiting season there was a substantial shortfall in realisation of existing potential due to inefficient fertilisation of ovules and poor berry development.The analysis indicates three phases of development where factors not yet examined can have a large effect on yield.     

Milk fever in dairy cows: a review of pathophysiology and control principles

The periparturient or transition period of 4 weeks before and 4 weeks after calving is characterised by a greatly increased risk of disease. Hypocalcaemia around calving is a risk factor for many of these diseases and is an indirect risk factor for increased culling. The incidence of clinical hypocalcaemia (milk fever) in the field generally ranges from 0-10%, but may exceed 25% of cows calving. In research trials conducted on milk fever the incidence has approached 80% of cows calving. Homeostasis of calcium (Ca) is regulated by calcitonin, parathyroid hormone and 1,25(OH)(2) vitamin D(3). Age increases the risk of milk fever by approximately 9% per lactation. Control of milk fever has revolved around stimulation of homeostatic mechanisms through feeding a pre-calving diet low in Ca. More recently, the role of the dietary cation anion difference (DCAD) in the prevention of Ca disorders has been examined, both by field research and meta-analysis. The most appropriate form of the DCAD equation has been contentious, but recent meta-analyses have shown that the equation (Na(+)+K(+))-(Cl(-)+S(2-)) is most effective for predicting milk fever risk. Decreased risk of milk fever is linear with DCAD, whereas the effect of DCAD on urinary pH is curvilinear. A pivotal role of providing dietary magnesium (Mg) before calving has been confirmed by meta-analysis, and a quadratic effect of Ca on milk fever risk was found with a peak occurring with dietary levels of 1.1-1.3% of dry matter. Risks of milk fever increase with increased dietary phosphorus (P) fed pre-calving and with increasing days of exposure to a pre-calving diet. Meta-analysis has revealed that the important roles of dietary Ca, Mg and P, as well as the duration of exposure to the pre-calving diet in milk fever control strategies are independent of DCAD. Studies on the effect of exposure to well designed pre-calving diets have shown that substantial improvements in production, reproduction and animal health can be made but further examination of the influence of the period of exposure to different diets is warranted.     

Effects of Simulated Acid Mist on a Sitka Spruce Forest Approaching Canopy Closure: Significance of Acidified Versus Non-Acidified Nitrogen Inputs

Effects of enhanced N, S and NS Acid additions, up to approximately 100 kg N and S ha^?1 y^?1, are described for a 15-year-old Sitka spruce forest growing on an acid peat in Scotland. Groups of 10 trees, replicated over 4 blocks, have been treated at canopy height on approximately 50 or 100 occasions with 2 mm precipitation equivalent, between April and November, since 1996. Relative stem volume increment (RSVI) has been consistently higher in the NS Acid treated trees compared with control or N treated trees since the second year of treatment, although no dose response was found. Litterfall was also considerably increased in the NS Acid treatments and showed a clear dose effect but was not correlated with RSVI. Base cation concentrations in soil waters, collected using zero tension lysimeters reflected the presence or absence of the spray treatments and showed a dose related increase in response to NS Acid inputs. Treatment with 2NS Acid increased NH₄-N and NO₃-N by an order of magnitude. Results after 4 years of treatment showed a positive growth and litterfall response to NS Acid inputs but no effect of N alone. Enhanced stemwood growth may be linked to the higher base cation and phosphate concentrations measured in the soil water in the presence of NS Acid and S treatments.     

沉睡中的印度花卉产业何时醒来？

2007年末,笔者应邀出席了首次在印度浦那市举办的花卉展览,该展览由种植者自发组织而没有政府参与,这在印度是比较少见的。展览为印度各地区展示其最佳花卉作品提供了一个很好的平台,各个领域的育种家代表也参加了本次展览。虽然此次活动不是由政府组织的,但也不能忽视政府在国家花卉产业发展上的促进作用。热衷于园艺事业、以对花卉产业作出很大贡献闻名的浦那市长瑞娜西米-巴西尔（Rajlakshmi Bhosale）对本次展览给予了充分肯定。     

Potential new genes for resistance to <Emphasis Type="Italic">Mycosphaerella graminicola</Emphasis> identified in <Emphasis Type="Italic">Triticum aestivum</Emphasis> × <Emphasis Type="Italic">Lophopyrum elongatum</Emphasis> disomic substitution lines

Lophopyrum species carry many desirable agronomic traits, including disease resistance, which can be transferred to wheat by interspecific hybridization. To identify potentially new genes for disease and insect resistance carried by individual Lophopyrum chromosomes, 19 of 21 possible wheat cultivar Chinese Spring × Lophopyrum elongatum disomic substitution lines were tested for resistance to barley yellow dwarf virus (BYDV), cereal yellow dwarf virus (CYDV), the Hessian fly Mayetiola destructor, and the fungal pathogens Blumeria graminis and Mycosphaerella graminicola (asexual stage: Septoria tritici). Low resistance to BYDV occurred in some of the disomic substitution lines, but viral titers were significantly higher than those of two Lophopyrum species tested. This suggested that genes on more than one Lophopyrum chromosome are required for complete resistance to this virus. A potentially new gene for resistance to CYDV was detected on wheatgrass chromosome 3E. All of the substitution lines were susceptible to Mayetiola destructor and one strain of B. graminis. Disomic substitution lines containing wheatgrass chromosomes 1E and 6E were significantly more resistant to M. graminicola compared to Chinese Spring. Although neither chromosome by itself conferred resistance as high as that in the wheatgrass parent, they do appear to contain potentially new genes for resistance against this pathogen that could be useful for future plant-improvement programs.     

A demonstration of the inheritance of field resistance to lettuce downy mildew (Bremia lactucae Regel.) in progeny derived from cv. Grand Rapids

Summary The inheritance of field resistance to downy mildew in lettuce derived from cv. Grand Rapids was studied in F₂, F₃ and F₄ progeny from a cross with the more susceptible cv. Lobjoits Green Cos. The results for 32 randomly produced F₃ families and the F₂ population corresponded closely although the absolute level of resistance varied from season to season according to disease pressure and environmental conditions. The field resistance character showed a quantitative pattern of inheritance but the rapid response to selection at F₃ implied that only a few genes may be involved. F₄ families raised from families selected from the two extremes of the F₃ distribution fell into distinct categories with resistance levels corresponding to that of their F₃ parents. An association between resistance and morphological features of the resistant parent was present at F₂ but not in subsequent generations when individuals and families which were as resistant as cv. Grand Rapids and yet bore little morphological resemblance to this cultivar were readily recovered.