Developmentally dependent expression of tissue specific amylases in maize

Summary The mapping of three genes (speA, speB and metK) involved in the biosynthesis of spermidine is described. They are located between minutes 56 and 57 on the linkage map of Escherichia coli. The clustering of these genes suggests the possibility of an operon for spermidine synthesis. Two other genes, argP, controlling the production of an arginine permease, and can, conferring resistance to canavanine, were found to be located in the same region.     

An improved colony hybridization method with significantly increased sensitivity for detection of single genes

By introducing a simple modification of existing methods, colony hybridization has been used to detect single copy genes coding for a heat-stable enterotoxin in wild-type strains isolated from patients with diarrhea. The modification described in this communication results in an approximately 100-fold increase in sensitivity, probably by increasing the total denatured plasmid DNA fixed to the paper.     

In vitro response of strawberry cultivars and regenerants to Colletotrichum acutatum

Diseases affecting strawberry (Fragaria × ananassa Duch.) have been of major concern in recent years because of their widespread occurrence and potential for yield loss. Anthracnose, caused by the fungus Colletotrichum acutatum, is one of the most serious diseases of strawberry worldwide. Tissue-culture induced (somaclonal) variation provides one strategy for generating disease-resistant genotypes. As part of a program to generate strawberry germplasm resistant to anthracnose, an in vitro screening system was used to evaluate several commercial cultivars, Chandler, Delmarvel, Honeoye, Latestar, Pelican and Sweet Charlie propagated in vitro, and shoots regenerated from leaf explants of these cultivars for resistance to C.␣acutatum isolate Goff (highly virulent). Regenerants with increased levels of resistance were identified from all of the cultivars. The greatest increases in disease resistance were observed for regenerants from leaf explants of cultivars Pelican and Chandler that exhibited 17.5- and 6.2-fold increases in resistance, respectively. The highest levels of anthracnose resistance (2 to 6% leaf necrosis) were exhibited by regenerants from explants of cultivars Pelican and Sweet Charlie. These studies suggest that generating somaclonal variation may be a viable approach to obtaining strawberry plants with increased levels of anthracnose resistance.     

Processed Manure as Carrier to Introduce Trichoderma harzianum: Population Dynamics and Biocontrol Effect on Rhizoctonia solani

Manure pellets produced from processed swine faeces can be used as carrier material for the biocontrol fungus Trichoderma harzianum. The antagonist can grow and sporulate on the processed manure powder as the sole source of carbon and nutrients. The incorporation of conidia in pellets of the processed manure was shown to be feasible on a laboratory scale. Survival of the fungus in the pellets during storage was satisfactory. The population dynamics of T. harzianum were studied using a benomyl-resistance marker after introduction of conidia into soil. The antagonist could colonize and spread through a number of non-sterile soils and was able to establish a stable population over a period exceeding 125 days. Under sterile conditions, the propagation of T. harzianum in soil was much greater than under non-sterile conditions. The incorporation of antagonist conidia in pellets was found to be essential for the successful colonization of non-sterile soil. In growth chamber experiments, application of T. harzianum via processed manure pellets reduced damping-off of sugar beet seedlings caused by Rhizoctonia solani in artificially and naturally infested soil. In artificially infested soil, T. harzianum reduced the population of R. solani and protected beet seedlings from damping-off 3 weeks after introduction. The application of T. harzianum to naturally infested soil increased the number of healthy beet seedlings more than two-fold.     

The use of an oligonucleotide that hybridizes to DNA sequences interspersed in the genome of members of the genusPhytophthora as an adjunct to morphological criteria in species identification

An oligonucleotide (primer), designed from a conserved region of the multi-allelicb locus of the basidiomycete fungusUstilago maydis, generated reproducible PCR fingerprints inPhytophthora species. The primer hybridized in a species-specific manner to nucleotide sequences interspersed in the genome of the closely related members ofPhytophthora taxonomic group IV. We recommend the use of this PCR procedure as an alternative method for resolving the close taxonomic affinity of some members of the genusPhytophthora.