Role of Alanine Racemase Mutations in Mycobacterium tuberculosis d-Cycloserine Resistance.

A screening of more than 1,500 drug-resistant strains of Mycobacterium tuberculosis revealed evolutionary patterns characteristic of positive selection for three alanine racemase (Alr) mutations. We investigated these mutations using molecular modeling, in vitro MIC testing, as well as direct measurements of enzymatic activity, which demonstrated that these mutations likely confer resistance to d-cycloserine

Establishment of lucerne (Medicago sativa) sown on five dates with four inoculation treatments

The establishment and growth of ‘Stamina 5’ lucerne (Medicago sativa) seed sown with three inoculant carriers (ALOSCA®, coated, and peat slurry treated) or as bare seed (control) on five dates (21 October 2010, 9 November 2010, 8 December 2010, 13 January 2011 and 3 February 2011) was investigated on a Lismore stony silt loam soil at Ashley Dene dryland research farm in Canterbury. Initial lucerne populations were 300 plants m⁻² from coated seed and on average 200 ± 11.2 plants m⁻² from bare seed, ALOSCA® and the peat slurry inoculated seed. The higher population from coated seed treatments did not confer a herbage yield advantage. In the establishment year, yield was lowest (0.59 t DM ha⁻¹) from the last sowing (3 February 2012) and highest from sowing dates (SD) 2 and 3 (2.6 ± 0.12 t DM ha⁻¹). Yields were restricted by the low volumetric soil moisture content from November until March. The declining autumn photoperiod (14.9 to 14.1 hours) probably increased the partitioning priority of assimilates to the roots, reducing the above ground DM in the later sowing dates. In most cases, DM yields in Year 1 were unaffected by seed inoculant treatments. In Year 2, DM production from the peat slurry treated seed (8.0 t ha⁻¹) was highest, while coated seed crops were lowest (6.0 t ha⁻¹). The effects of sowing date carried through to the second year with lower DM yields from SD4 and SD5 (6.0 ± 0.18 t ha⁻¹) compared with 7.3 ± 0.18 t ha⁻¹ from the earlier sowing dates

Yield, final population and emergence of seed treated lucerne (Medicago sativa L.) sown on five dates

Dryland seedling lucerne establishment was examined at Lincoln University, Canterbury, New Zealand. Stands were sown on 4 October, 4 November, 2 December 201 O and 10 January and 7 February 2011 with four seed treatments; bare seed, ALOSCA ® granules, coated seed and peat inoculant. Accumulated crop dry matter (DM) yield decreased with each successive sowing from 15 t/ha to 2.5 t/ha for the latest sowing date. Lower DM yields were explained by less intercepted light and a change in DM partitioning from shoots to roots. The latest sowing grew 1.84±0.26 kg DM/ °Cd compared with 3.84±0.22 kg DM/ °Cd for the earliest sowing. Coated seed produced a higher (P<0.001) initial plant population of 331 plants/m2 which was 68% of the 490 seeds/m2 sown. It also had the highest population 12 months later although seedling numbers had declined by 27%. Thus, adequate plant populations were established from all sowing dates and seed treatments including the bare seed contro

Effectiveness of three inoculation methods for lucerne (Medicago sativa L.) in two Canterbury soils

The efficacy of ALOSCA®, coated and peat seed inoculant treatments on the nodulation of lucerne sown in two soils in Canterbury, New Zealand was investigated. The commercial inoculant was Sinorhizobium meliloti strain RRI128. It was recovered from the nodules of lucerne plants grown from ALOSCA®, peat and coated seed at both sites. Coated seed had the highest nodule occupancy with 45% and 47% of nodules containing S. meliloti strain RRI128 at the Ashley Dene and Lincoln University field sites, respectively. ALOSCA® had only 9% and 16% of nodules from the Ashley Dene and Lincoln University field sites, respectively, containing S. meliloti strain RRI128. Naturalised Rhizobium strains were also recovered from the nodules of lucerne plants grown from ALOSCA®, coated and peat seed inoculant treatments. A single genotype (genotype A) of a Rhizobium sp. was recovered more frequently than the inoculated S. meliloti strain in the nodules of plants grown from peat treated seed at Lincoln University (30% vs 22%) and in the nodules of ALOSCA® treated seed at Ashley Dene (54% vs 9%). Bare seed was also nodulated by the Rhizobium sp. genotype A with 57% and 28% of nodules from plants grown from uninoculated seed at Ashley Dene and Lincoln University, respectively, containing this strain. This research shows delivery by an appropriate inoculation treatment is required to maximise occupancy by the commercial strain

Sowing date affected shoot and root biomass accumulation of lucerne during establishment and subsequent regrowth season

© 2015 Elsevier B.V. The pattern of perennial dry matter (DM) was manipulated over two seasons to determine if the establishment of lucerne (Medicago sativa L.) is regulated by the demand for assimilate by perennial organs, (taproot plus crown) or crop ontogeny. Crops of 'Stamina 5' lucerne were established from spring to late summer at two sites which differed by 230mm to 2.3m soil depth in plant available water content (PAWC) at Lincoln University, New Zealand. The establishment phase was characterised from sowing until crops reached a maximum accumulation of perennial biomass of ~5tDMha -1 . Demand for biomass offered insight into the variability in fractional partitioning of DM to the perennial organs (P root ) during establishment. This showed that P root was 0.48 until a perennial biomass of 2.9±0.28tDMha -1 . Lucerne continued to partition DM to the perennial organs until a maximum biomass of ~5tDMha -1 , but at a decreasing rate shown by a linear decline in P root in response to increasing perennial biomass . This meant P root was independent of crop ontogeny, but most likely still under the control of environmental influences, and the establishment phase extended into the second season for crops which had not attained a perennial biomass > 3tDMha -1 . These crops continued to prioritise the allocation of DM to the perennial organs which explained the 20-25% decrease in shoot yield in the second season when sowing was delayed. This study quantified the establishment phase of lucerne to perennial biomass demand as independent of crop ontogeny. It showed establishment was regulated by biomass demand of these perennial organs. The spring sown crops on the High PAWC soils completed this phase at the earliest in 4 months. In contrast, autumn sown crops on the Low PAWC soils took nearly 9 months to complete this phase. These results indicate different management strategies may be required to establish lucerne rather than solely using first flowering as a sign that the establishment phase is complete. Results can be incorporated into the current partitioning framework to improve the simulation modelling of lucerne