ABSTRACT
A major challenge facing agriculture in the 21st century is the need to increase the productivity of cultivated land while reducing the environmentally harmful consequences of mineral fertilization. The microorganisms thriving in association and interacting with plant roots, the plant microbiota, represent a potential resource of plant probiotic function, capable of conjugating crop productivity with sustainable management in agroecosystems. However, a limited knowledge of the organismal interactions occurring at the root-soil interface is currently hampering the development and use of beneficial plant-microbiota interactions in agriculture. Therefore, a comprehensive understanding of the recruitment cues of the plant microbiota and the molecular basis of nutrient turnover in the rhizosphere will be required to move toward efficient and sustainable crop nutrition. In this chapter, we will discuss recent insights into plant-microbiota interactions at the root-soil interface, illustrate the processes driving mineral dynamics in soil, and propose experimental avenues to further integrate the metabolic potential of the plant microbiota into crop management and breeding strategies for sustainable agricultural production.
Subject(s)
Bacteria/metabolism , Microbiota , Minerals/metabolism , Plant Roots/microbiology , Plants/microbiology , Bacteria/classification , Bacteria/isolation & purification , Bacterial Physiological Phenomena , Minerals/analysis , Rhizosphere , Soil MicrobiologyABSTRACT
Recessive mlo alleles of the barley Mlo gene confer resistance to almost all known isolates of the powdery mildew fungal pathogen targeting barley (Hordeum vulgare). To characterize haplotypes present in the Mlo chromosomal region of cultivated Mlo and mlo barley genotypes, we conducted a polymorphism search in 3 predicted low-copy sequence regions adjacent to the Mlo gene by examining a sample of 4 Mlo and 3 mlo cultivars. Eight single-nucleotide polymorphisms (SNPs) and 1 insertion-deletion (indel) were detected, and easy to use PCR-based markers were developed for typing the SNPs. The PCR markers were used to characterize a collection of 46 Mlo and 25 mlo barley cultivars, identifying 3 distinct mlo-11 haplotypes, 1 mlo-9 haplotype, and 4 Mlo haplotypes. We summarized the haplotype and marker information obtained here and in a previous study to help breeders identify strategies for mlo marker-assisted selection. The ability of the markers to identify mlo-resistant genotypes in segregating populations was demonstrated using 2 resistance-characterized F2 populations derived by 3-way crosses.
Subject(s)
Ascomycota/pathogenicity , Genes, Plant , Hordeum/genetics , Hordeum/microbiology , Plant Proteins/genetics , Alleles , Base Sequence , Breeding , Crosses, Genetic , DNA, Plant/genetics , Genetic Markers , Haplotypes , Plant Diseases/genetics , Plant Diseases/microbiology , Polymerase Chain Reaction , Polymorphism, Single Nucleotide , Selection, GeneticABSTRACT
The dominant gene Rdg2a of barley conferring resistance to the hemi-biotrophic seed-borne pathogen Pyrenophora graminea is located in the distal region of chromosome arm 1 (7H)S. As the first step towards isolating the gene, a high-resolution genetic map of the region was constructed using an F(2) population of 1,400 plants (Thibaut Rdg2axMirco). The map included six classes of resistance gene analogues (RGAs) tightly associated with Rdg2a. Rdg2a was delimited to a genetic interval of 0.14 cM between the RGAs ssCH4 and MWG851. Additional markers were generated using the sequence from the corresponding region on rice chromosome 6, allowing delimitation of the Rdg2a syntenic interval in rice to a 115 kbp stretch of sequence. Analysis of the rice sequence failed to reveal any genes with similarity to characterized resistance genes. Therefore, either the rice-barley synteny is disrupted in this region, or Rdg2a encodes a novel type of resistance protein.
Subject(s)
Chromosome Mapping , Genes, Plant/genetics , Hordeum/genetics , Immunity, Innate/genetics , Ascomycota/immunology , Crosses, Genetic , DNA Primers , Genetic Markers , Hordeum/microbiology , Oryza/genetics , Plant Diseases/microbiology , Polymorphism, Restriction Fragment Length , Random Amplified Polymorphic DNA Technique , Synteny/geneticsABSTRACT
We describe the use of a magnetic search coil technique for measuring the movement of prosthetic eyes. The technique allows for accurate comparison of implant designs and surgical techniques.
Subject(s)
Electrooculography/methods , Eye Movements , Eye, Artificial , Adolescent , Adult , Aged , Eye, Artificial/history , Female , History, 19th Century , History, 20th Century , Humans , Male , Middle Aged , Prosthesis Design/historyABSTRACT
Ninety-four consecutive persons with unilateral enucleations or eviscerations were tested by the Schirmer I and Schirmer II tests for tear production. The findings on the artificial eye were compared with those on the companion, living (control) eye. The collected data were subjected to statistical analysis. The control eyes were shown to respond in the normal manner, more tears without topical anesthetic than with it. The sockets of artificial eyes produced no more tears without anesthetic than with it. The control eyes produced a normal amount of reflex tears, whereas the sockets of many artificial eyes produced practically no reflex tears. Tear production in persons with no complaints was compared to those with noteworthy problems. Persons with problems had only half as much basic tear secretion as those without problems. Elimination of the stimulus to reflex tear production by removal of the cornea and by the presence of the prosthesis is suggested as the cause of dryness of the eye socket. The potential value of aqueous or oily artificial lubricants is mentioned.