Development of a marker assisted selection program for cacao

ABSTRACT Production of cacao in tropical America has been severely affected by fungal pathogens causing diseases known as witches' broom (WB, caused by Moniliophthora perniciosa), frosty pod (FP, caused by M. roreri) and black pod (BP, caused by Phytophthora spp.). BP is pan-tropical and causes losses in all producing areas. WB is found in South America and parts of the Caribbean, while FP is found in Central America and parts of South America. Together, these diseases were responsible for over 700 million US dollars in losses in 2001 (4). Commercial cacao production in West Africa and South Asia are not yet affected by WB and FP, but cacao grown in these regions is susceptible to both. With the goal of providing new disease resistant cultivars the USDA-ARS and Mars, Inc. have developed a marker assisted selection (MAS) program. Quantitative trait loci have been identified for resistance to WB, FP, and BP. The potential usefulness of these markers in identifying resistant individuals has been confirmed in an experimental F(1) family in Ecuador.     

Mechanical injury and fungal infection induce acquired resistance in Norway spruce

Norway spruce trees (Picea abies (L.) Karst.) pretreated by wounding and fungal infection showed highly enhanced resistance to a subsequent challenge inoculation with the pathogenic bluestain fungus Ceratocystis polonica (Siem.) C. Moreau. This is the first time the effectiveness of the constitutive and inducible defenses has been shown to depend on prior wounding and infection in conifers, although such acquired resistance has previously been found in several angiosperms. Trees that were pretreated with a combination of 12 bark wounds (1.6 x 10 cm), four fungal inoculations and four sterile inoculations 1-15 days before mass inoculation with C. polonica at 400 inoculations per square meter over a 0.8 m stem section had significantly shorter necroses in the phloem, less bluestained sapwood, and less dead cambium than untreated control trees. Pretreatment with four fungal or sterile inoculations alone did not lead to enhanced resistance. Pretreatment by bark wounding alone seemed to provide an intermediate degree of resistance compared to bark wounding, fungal inoculations and sterile inoculations combined. All trees had a marked increase in the number of resin ducts in the year of inoculation compared with previous years, suggesting that formation of traumatic resin ducts play an important role in the development and maintainance of enhanced resistance.     

The molecular basis of the sparse fur mouse mutation

The ornithine transcarbamylase-deficient sparse fur mouse is an excellent model to study the most common human urea cycle disorder. The mutation has been well characterized by both biochemical and enzymological methods, but its exact nature has not been revealed. A single base substitution in the complementary DNA for ornithine transcarbamylase from the sparse fur mouse has been identified by means of a combination of two recently described techniques for rapid mutational analysis. This strategy is simpler than conventional complementary DNA library construction, screening, and sequencing, which has often been used to find a new mutation. The ornithine transcarbamylase gene in the sparse fur mouse contains a C to A transversion that alters a histidine residue to an asparagine residue at amino acid 117.     

Toxoplasmosis in two cats with inflammatory intestinal disease

Lymphocytic-plasmacytic enteritis, a chronic inflammatory intestinal disease, was diagnosed in 2 cats. In 1 cat, recurrence of clinical signs after initiating treatment was attributed to relapse of the inflammatory intestinal disease, but was found to be attributable to relapsing toxoplasmosis secondary to immunosuppressive drug therapy. Treatment with clindamycin resolved the recurrent toxoplasmosis. In the second cat, clinical signs of toxoplasmosis did not develop, but serologic testing yielded evidence of active toxoplasmosis. Treatment with clindamycin caused the titers to decrease. Relapsing toxoplasmosis may be responsible for apparent resistance to treatment in cats for inflammatory intestinal disease being treated with immunosuppressive drugs.     

Influence of ectomycorrhization and cesium/potassium ratio on uptake and localization of cesium in Norway spruce seedlings

Norway spruce (Picea abies (L.) Karst.) seedlings growing in a growth pouch system were used to investigate the effects of the ectomycorrhizal fungus Hebeloma crustuliniforme (Bull. ex St. Amans) Quél. and various Cs/K ratios on the uptake of (134)Cs, expressed as a percentage of the total amount of (134)Cs supplied. The amount of (134)Cs taken up by seedlings increased with increasing Cs/K ratio. At a Cs/K ratio of 0.1, uptake of (134)Cs ranged between 7.2 and 7.3% and was independent of ectomycorrhizal status, whereas at Cs/K ratios >/= 1 uptake of (134)Cs varied from 8.1 to 11.1% for ectomycorrhizal and from 10.4 to 14.4% for non-inoculated plants. Ectomycorrhizal seedlings contained a lower concentration of (134)Cs than non-inoculated seedlings. Among plant parts, the amount of (134)Cs was significantly lower in needles and lateral roots of ectomycorrhizal seedlings compared with non-inoculated seedlings. Among fungal and seedling tissues, highest X-ray net counts of (133)Cs were measured in fungal hyphae of ectomycorrhizal mantles. X-Ray net counts of (133)Cs in lateral roots of ectomycorrhizal and non-inoculated plants were similar, but 5 to 10 times higher than in main roots and needles, suggesting an accumulation of (133)Cs in lateral roots and slow translocation to other plant parts. In contrast, X-ray net counts of K indicated that K was readily mobilized from lateral roots to main roots and needles. Elemental mapping showed a relatively homogeneous distribution of (133)Cs within the root.