Cytoplasmic and nuclear genetic components of membrane stability of winter wheat plants exposed to sub‐zero temperatures

Winter wheat (Triticum aestivum L.) is seeded in the autumn and harvested the following summer, and therefore, must survive multiple episodes of subfreezing temperatures throughout the winter months. Cellular membrane stability following exposure to subfreezing temperatures contributes to the ability to survive these episodes. This study investigated the inheritance of the ability to tolerate subfreezing temperatures with a seven‐parent diallel cross analysis of cellular membrane integrity as measured by electrolyte leakage after exposure to ?10 or ?14 °C. Significant differences in membrane stability were found among the parent lines. The inheritance of the freezing tolerance as measured by electrolyte leakage was complex and characterized by significant additive, dominant and cytoplasmic effects. General combining ability, indicative of additive genetic effects, were significant at both test temperatures, but accounted for 25.5% of the variance at the ?10° C test temperature, and only 4% of the variance at the ?14 °C test temperature. Specific combining ability, indicative of genetic dominance effects, were significant at both test temperatures, but accounted for only 14.6% of the variance at the ?10 °C test temperature, and 38% of the variance at the ?14 °C test temperature. Reciprocal (cytoplasmic) effects were significant and accounted for about 20% of the variance at both test temperatures. Cytoplasmic effects contributing to greater membrane stability were especially apparent in the cultivar Tiber when crossed to Masami, Lewjain, or Hatton. These results suggest that efforts to improve freezing tolerance are complicated by differing gene action at different test temperatures and also may benefit from identifying specific combinations of nuclear and cytoplasm sources that are most conducive to membrane stability following freezing.     

Anther Culture in Rye: Improved Plant Regeneration Using Modified MS-Media

The use of androgenetic doubled haploids in rye breeding is still limited by low regeneration rates. In this study we tested the influence of two modified MS-media on the number of reacting anthers and on plant regeneration. Picloram and 2,4-D were used as auxin components in the induction media. The highest induction rates (reacting anthers per 100 cultivated anthers) and the highest regeneration rates (number of green plants per 100 cultivated anthers) were reached on a modified MS-medium containing Picloram as auxin source, regardless of the donor plant material. The comparison of the results obtained with the single cross ‘SC 35’ which contains genes of Secale vavilovii and the true Secale cereale donor forms clearly show the genotypic influence of donor plant material on induction and regeneration ability.     

Adoption potential of selected organic resources for improving soil fertility in the central highlands of Kenya

Soil fertility decline is the major cause of declining crop yields in the central highlands of Kenya and elsewhere within the African continent. This paper reports a study conducted to assess adoption potential of two leguminous trees, two herbaceous legumes, cattle manure, and Tithonia diversifolia either solely applied or combined with inorganic fertilizer, for replenishing soil fertility in the central highlands of Kenya. The study examined biophysical performance, profitability, feasibility and acceptability, and farmers experiences in managing and testing the inputs. The study was based on a series of studies incorporating both sociological and experimental approaches for two and a half years. Results of on farm trials showed that manure + fertilizer and tithonia + fertilizer treatments increased yields by more than 100% above the control. These treatments were the most profitable having highest net benefits and benefit cost ratios. They were also the most commonly preferred by farmers who used them on larger plots compared to the other inputs. In conclusion, cattle manure and tithonia were found to be the organic materials with the highest adoption potential for soil fertility improvement in this area. Calliandra calothyrsus and Leucaena trichandra, on the other hand, have potential for use as animal fodder. The herbaceous legumes had the least adoption potential due to poor performance recorded on the farms that possibly led to low preference by the farmers. However, issues of sustainable seed production could have played a role. This study recommends some policy issues for enhancing adoption and research issues focusing on exploring strategies for increasing biomass production and use efficiency on farms. Andre Bationo was formerly working for Tropical Soil Biology and Fertility Institute of CIAT (TSBF-CIAT) as the African network Coordinator.     

Effect of long term crop rotations and rewetting of soil on stability

Abstract. Soils, of clay texture, were taken from two crop rotations in a long term trial, (i) maize - spring oats - maize, (ii) maize - spring oats - autumn oats - red clover, and from an adjacent uncropped fenceline. Wet sieving was preceded by wetting under vacuum, wetting under tension or by direct immersion. The undisturbed soil was the most stable; the inclusion of clover in the rotation improved aggregate stability. Direct immersion was most disruptive in disintegrating aggregates followed by vacuum and pre-wetting under tension.     

Phloem mobility of xenobiotics VI. A phloem-mobile pro-nematicide based on oxamyl exhibiting root-specific activation in transgenic tobacco

Phloem mobility is a desirable attribute for pesticides in many applications, and the physicochemical properties necessary for phloem mobility are now well understood. However, attempts to derivatize pesticides to make them phloem mobile are often frustrated by a concomitant loss of activity. This study describes a phloem-mobile pro-nematicide, a hydroxymethyloxamyl glucuronide (JR522) coupled with an in-situ activation mechanism in transgenic tobacco expressing Escherichia coli β-glucuronidase in its root tips. When applied foliarly to the transgenic tobacco, JR522 and its methyl ester (JM775) showed greater nematicidal activity than oxamyl against root-knot nematodes. This example of combining pro-pesticide chemistry with crop genetic engineering for site-specific activation provides a model system for demonstrating how to circumvent the often mutual exclusivity of phloem mobility and pesticidal activity. Additional advantages of this scheme include the potential mammalian safety of the propesticide, as exhibited by JR522 in this study, and a high degree of site-specific release of xenobiotics in plants.     

Variability in the phloem restricted plant trypanosomes (Phytomonas spp) associated with wilts of cultivated crops

Plant trypanosomatids (Phytomonas spp) have been isolated from the crude sap of coconut tress and oil palm trees affected with Hartrot or Marchitex diseases in South America andAlpinia purpurata affected with wilt in the Caribbean. They are also commonly isolated from the fruits and latex of Euphorbiaceae or Asclepiadaceae. Thirty-fourPhytomonas stocks were studied by isoenzyme electrophoresis (11 loci) in order to investigate genetic variability in the intraphloemic group. Our results showed that variability in phloem restrictedPhytomonas is very high, and that Marchitez or Hartrot associated trypanosomatids are not readily separated into two distinct groups. Moreover, the two isolates fromAlpinia are very close to the other intraphloemic isolates. The results confirm the existence of several distinct groups, comprising of at least 2 groups of phloem restricted trypanosomatids, not related to the host species, 3 groups of latex trypanosomatids, and one group of fruit trypanosomatids.     

Platelet function and association of bovine viral diarrhea virus with platelets of persistently infected cattle

OBJECTIVE: To determine whether viral involvement with platelets obtained from cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV) is associated with altered platelet function or decreased platelet counts. SAMPLE POPULATION: Platelets obtained from 8 cattle PI with BVDV and 6 age-, sex-, and breed-matched uninfected control cattle. PROCEDURE: Manual platelet counts were determined, and platelet function was assessed through optical aggregometry by use of the aggregation agonists ADP and platelet-activating factor. Identification of BVDV in serum and preparations of purified platelets was determined by use of virus isolation tests. RESULTS: No significant difference in platelet counts was detected between cattle PI with BVDV and control cattle. In response to the aggregation agonists, maximum aggregation percentage and slope of the aggregation curve were not significantly different between cattle PI with BVDV and control cattle. We isolated BVDV from serum of all PI cattle and from purified platelets of 6 of 8 PI cattle, but BVDV was not isolated from serum or platelets of control cattle. CONCLUSIONS AND CLINICAL RELEVANCE: Isolation of BVDV from platelets in the peripheral circulation of cattle immunotolerant to BVDV does not result in altered platelet function or decreases in platelet counts.     

Correlation between hepatobiliary scintigraphy and surgery or postmortem examination findings in dogs and cats with extrahepatic biliary obstruction, partial obstruction, or patency of the biliary system: 18 cases (1995-2004)

OBJECTIVE: To evaluate the usefulness of serum biochemical variables and scintigraphic study results for differentiating between dogs and cats with complete extrahepatic biliary obstruction (EHO) and those with partial EHO or patent bile ducts. STUDY DESIGN: Retrospective case series. ANIMALS: 17 dogs and 1 cat. PROCEDURE: Animals that underwent hepatobiliary scintigraphy and had either surgical or postmortem confirmation of the degree of bile duct patency were included. Scintigraphic images were evaluated and biliary tracts were classified as patent, partially obstructed but patent, or obstructed. Surgery or postmortem examination was considered the gold standard for diagnosis, and compared with those findings, sensitivity and specificity of scintigraphy were calculated. RESULTS: With absence of radioactivity in the intestinal tract as the diagnostic criterion for EHO, the sensitivity and specificity of scintigraphic diagnosis were both 83% when final images were acquired at 19 to 24 hours, compared with 100% and 33%, respectively, when 180 minutes was used as the cutoff time. Animals with partial biliary obstruction had less intestinal radioactivity that arrived later than that observed in animals with patent biliary tracts. CONCLUSIONS AND CLINICAL RELEVANCE: Animals in which intestinal radioactivity has not been observed after the standard 3 to 4 hours should undergo additional scintigraphic imaging. Findings in animals with partial biliary obstruction include delayed arrival of radioactivity and less radioactivity in the intestine. Distinguishing between complete and partial biliary tract obstruction is important because animals with partial obstruction may respond favorably to medical management and should not be given an erroneous diagnosis of complete obstruction.