Basal root whorl number: a modulator of phosphorus acquisition in common bean (Phaseolus vulgaris)

BACKGROUND AND AIMS

Root architectural phenes enhancing topsoil foraging are important for phosphorus acquisition. In this study, the utility of a novel phene is described, basal root whorl number (BRWN), that has significant effects on topsoil foraging in common bean (Phaseolus vulgaris).

METHODS

Whorls are defined as distinct tiers of basal roots that emerge in a tetrarch fashion along the base of the hypocotyl. Wild and domesticated bean taxa as well as two recombinant inbred line (RIL) populations were screened for BRWN and basal root number (BRN). A set of six RILs contrasting for BRWN was evaluated for performance under low phosphorus availability in the greenhouse and in the field. In the greenhouse, plants were grown in a sand-soil media with low or high phosphorus availability. In the field, plants were grown in an Oxisol in Mozambique under low and moderate phosphorus availability.

KEY RESULTS

Wild bean accessions tended to have a BRWN of one or two, whereas cultivated accessions had BRWN reaching four and sometimes five. BRWN and BRN did not vary with phosphorus availability, i.e. BRWN was not a plastic trait in these genotypes. Greater BRWN was beneficial for phosphorus acquisition in low phosphorus soil. Genotypes with three whorls had almost twice the shoot biomass, greater root length and greater leaf area than related genotypes with two whorls. In low phosphorus soil, shoot phosphorus content was strongly correlated with BRWN (R(2) = 0.64 in the greenhouse and R(2) = 0.88 in the field). Genotypes with three whorls had shallower root systems with a greater range of basal root growth angles (from 10 to 45 ° from horizontal) than genotypes with two whorls (angles ranged from 60 to 85 ° from horizontal).

CONCLUSIONS

The results indicate that BRWN is associated with increased phosphorus acquisition and that this trait may have value for selection of genotypes with better performance in low phosphorus soils.

Changes in the epidemiology of meticillin-resistant Staphylococcus aureus associated with the emergence of EMRSA-16 at a university hospital

This study investigated the molecular epidemiology of meticillin-resistant Staphylococcus aureus (MRSA) in the University Hospital of the Canary Islands (HUC) in order to evaluate epidemiological changes over a six-year period. Clinical and epidemiological data were collected between May 2000 and December 2003, and isolates were subjected to pulsed-field gel electrophoresis (PFGE), multi-locus sequence typing (MLST), SCCmec typing and spa typing. Since 2000, the rate of MRSA infections has increased at the HUC, coinciding with the emergence and spread of the EMRSA-16 clone (ST36-MRSA-II) and replacement of the Iberian clone (ST247-MRSA-I). Genotypic changes were associated with changes in the epidemiological profile. The mean age and proportion of patients over 60 years old (P=0.01) and the proportion of respiratory infections (P=0.001) increased significantly. Gentamicin and tetracycline susceptibility of MRSA isolates increased (P<0.001) following the emergence of EMRSA-16. Combining PFGE, SCCmec and MLST has been instrumental in understanding these changes and defining the clones circulating in the HUC patient population.

SEPs and CNS magnetic stimulation in syringomyelia

Somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) to transcranial and spinal stimulation from upper and lower limb muscles were elicited in 13 patients with syringomyelia. Seven had an associated Chiari type I anomaly. Diagnosis was confirmed by MRI. In 5 cases, SEPs and MEPs were performed before and after surgical treatment. Prolonged central motor conduction times or absent motor responses in upper or lower limbs were found in most patients. The greatest number of abnormalities was disclosed by measurement of CMCT followed by SEPs after tibial nerve stimulation. Two of 5 cases undergoing surgery improved clinically and showed reduction in CMCT after surgical treatment. Our study shows that MEPs were useful in the evaluation of neurophysiological status in syringomyelia patients, helping to estimate anterolateral spinal cord function.

Early treatment of familial hypophosphataemic rickets

A 2 1/2 year old girl in whom familial hypophosphataemic rickets was diagnosed at age 2 months, has been treated since then with oral 1 alpha,25-dihydroxycholecalciferol and phosphate. She has not, so far, developed osseous lesions.

[Use of Boyer's score in the differential diagnosis of meningitis]

Authors have studied reliability of Boyer's score for diagnosis of bacterial versus aseptic meningitis. This score is based upon clinical and biological data easily available in few hours since the patient's admission to hospital. They their have reviewed all cases of meningitis in hospital during the last four years. Boyer's score was very useful and its specificity (100%) and sensitivity (96,50%) were very high. Authors consider this test convenient and reliable for the presumptive diagnosis of the type of meningitis with its' therapeutic implications.

[Aicardi syndrome]

The association in young girls of flexion spasms of early beginning, partial or total agenesis of the corpus callosum, severe chororetinopathy and frequent skeletal anomalies is known as the Aicardi syndrome. On occasion of two observations a review of the literature is made.