Functional mutants of Azospirillum brasilense elicit beneficial physiological and metabolic responses in Zea mays contributing to increased host iron assimilation.

Iron (Fe), an essential element for plant growth, is abundant in soil but with low bioavailability. Thus, plants developed specialized mechanisms to sequester the element. Beneficial microbes have recently become a favored method to promote plant growth through increased uptake of essential micronutrients, like Fe, yet little is known of their mechanisms of action. Functional mutants of the epiphytic bacterium Azospirillum brasilense, a prolific grass-root colonizer, were used to examine mechanisms for promoting iron uptake in Zea mays. Mutants included HM053, FP10, and ipdC, which have varying capacities for biological nitrogen fixation and production of the plant hormone auxin. Using radioactive iron-59 tracing and inductively coupled plasma mass spectrometry, we documented significant differences in host uptake of Fe2+/3+ correlating with mutant biological function. Radioactive carbon-11, administered to plants as 11CO2, provided insights into shifts in host usage of 'new' carbon resources in the presence of these beneficial microbes. Of the mutants examined, HM053 exhibited the greatest influence on host Fe uptake with increased plant allocation of 11C-resources to roots where they were transformed and exuded as 11C-acidic substrates to aid in Fe-chelation, and increased C-11 partitioning into citric acid, nicotianamine and histidine to aid in the in situ translocation of Fe once assimilated.

Genetic Variation Among Isolates of the Web Blight Pathogen of Common Bean Based on PCR-RFLP of the ITS-rDNA Region.

Variability of 45 isolates of Rhizoctonia solani (teleomorph Thanatephorus cucumeris) causing web blight (WB) of common bean, Phaseolus vulgaris, was examined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the internal transcribed spacer regions (ITS1 and ITS2) and the 5.8S subunit (5.8S) of the nuclear ribosomal DNA repeat (ITS-5.8S-rDNA). Isolates were collected from diseased bean leaves from Argentina, Costa Rica, Cuba, Dominican Republic, Honduras, Panama, and Puerto Rico. These WB isolates belong to AG-1 and AG-2 based on anastomosis reaction. Isolates of AG-1 that cause WB were separated into three distinct groups of RFLP patterns from enzymatic digestion of a 740-bp PCR fragment. Microsclerotia-producing isolates (<1 mm) were differentiated from macrosclerotia-producing isolates (5 to 20 mm) based on PCR-RFLP patterns even though they are placed in the same AG1-1B subgroup by anastomosis reaction. WB isolates of AG-2 were separated into two distinct PCR-RFLP groups as previously reported. AG-1 macrosclerotial-producing isolates were the most virulent, whereas isolates of AG-2 were the least virulent. Genetic variability of the WB pathogen may have influenced the failure or success of management practices implemented in the past in Latin America.

Puerto Rican cultural beliefs: influence on infant feeding practices in western New York.

The purpose of this study was to examine the cultural beliefs and practices of Puerto Rican families that influence feeding practices and affect the nutritional status of infants and young children. The goal of the study was to outline strategies that would enable nurses to provide culturally congruent care for this population. Culture care theory guided the research, and an ethnonursing methodology was used. From interviews with 10 key and 5 general informants, 11 universal and 2 diverse themes were abstracted. The dimensions of kinship, cultural values, lifeways, and philosophical beliefs were found to influence Puerto Rican infant feeding practices. The cultural belief that big is healthy was found to be integrally related to cultural feeding practices. Strategies are suggested to facilitate provision of culturally congruent care for Puerto Rican infants and children in an ambulatory setting.