Phenotypic and molecular characterisation of novel Vicia faba germplasm with tolerance to acetohydroxyacid synthase-inhibiting herbicides (AHAS) developed through mutagenesis techniques.

BACKGROUND: Faba bean (Vicia faba L.) is an important crop in Australian farming systems, however, weed control is a major constraint due to a lack of in-crop broadleaf herbicide options. To address this, we developed acetohydroxyacid synthase (AHAS) inhibitor herbicide tolerance in faba bean using mutagenesis techniques. Dose-response experiments, agronomic field evaluation and DNA sequencing of the AHAS gene were used to quantify and validate tolerance traits. RESULTS: Four M2 faba bean single-plant biotypes (IMI-1, IMI-2, IMI-3 and IMI-4) at a frequency of 3.63 × 10-6 were successfully recovered. Molecular characterisation of the AHAS gene identified two known target site mutations (resulting in protein substitutions Ala205Val and Ser653Asn) conferring tolerance. Phenotypic characterisation found that both mutations conferred high levels of tolerance to the imidazolinone herbicide imazapyr. However, although the Ala205Val substitution showed improved levels of cross-tolerance to a range of sulfonylurea chemistries, the Ser653Asn substitution did not. In the field, IMI-3 showed the highest level of agronomic tolerance across a range of imidazolinone herbicides. CONCLUSIONS: Mutagenesis techniques were successful in the development of tolerance to AHAS inhibitor herbicides in faba bean, and could facilitate the first safe in-crop broadleaf herbicide control option in Australian faba bean production. © 2019 Society of Chemical Industry.

Molecular basis of adaptation to high soil boron in wheat landraces and elite cultivars.

Environmental constraints severely restrict crop yields in most production environments, and expanding the use of variation will underpin future progress in breeding. In semi-arid environments boron toxicity constrains productivity, and genetic improvement is the only effective strategy for addressing the problem. Wheat breeders have sought and used available genetic diversity from landraces to maintain yield in these environments; however, the identity of the genes at the major tolerance loci was unknown. Here we describe the identification of near-identical, root-specific boron transporter genes underlying the two major-effect quantitative trait loci for boron tolerance in wheat, Bo1 and Bo4 (ref. 2). We show that tolerance to a high concentration of boron is associated with multiple genomic changes including tetraploid introgression, dispersed gene duplication, and variation in gene structure and transcript level. An allelic series was identified from a panel of bread and durum wheat cultivars and landraces originating from diverse agronomic zones. Our results demonstrate that, during selection, breeders have matched functionally different boron tolerance alleles to specific environments. The characterization of boron tolerance in wheat illustrates the power of the new wheat genomic resources to define key adaptive processes that have underpinned crop improvement.

Ecological release from interspecific competition leads to decoupled changes in population and individual niche width.

A species's niche width reflects a balance between the diversifying effects of intraspecific competition and the constraining effects of interspecific competition. This balance shifts when a species from a competitive environment invades a depauperate habitat where interspecific competition is reduced. The resulting ecological release permits population niche expansion, via increased individual niche widths and/or increased among-individual variation. We report an experimental test of the theory of ecological release in three-spine stickleback (Gasterosteus aculeatus). We factorially manipulated the presence or absence of two interspecific competitors: juvenile cut-throat trout (Oncorhynchus clarki) and prickly sculpin (Cottus asper). Consistent with the classic niche variation hypothesis, release from trout competition increased stickleback population niche width via increased among-individual variation, while individual niche widths remained unchanged. In contrast, release from sculpin competition had no effect on population niche width, because increased individual niche widths were offset by decreased between-individual variation. Our results confirm that ecological release from interspecific competition can lead to increases in niche width, and that these changes can occur on behavioural time scales. Importantly, we find that changes in population niche width are decoupled from changes in the niche widths of individuals within the population.

Lactate, fructose and glucose oxidation profiles in sports drinks and the effect on exercise performance.

Exogenous carbohydrate oxidation was assessed in 6 male Category 1 and 2 cyclists who consumed CytoMax (C) or a leading sports drink (G) before and during continuous exercise (CE). C contained lactate-polymer, fructose, glucose and glucose polymer, while G contained fructose and glucose. Peak power output and VO2 on a cycle ergometer were 408+/-13 W and 67.4+/-3.2 mlO2 x kg(-1) x min(-1). Subjects performed 3 bouts of CE with C, and 2 with G at 62% VO2peak for 90 min, followed by high intensity (HI) exercise (86% VO(2)peak) to volitional fatigue. Subjects consumed 250 ml fluid immediately before (-2 min) and every 15 min of cycling. Drinks at -2 and 45 min contained 100 mg of [U-(13)C]-lactate, -glucose or -fructose. Blood, pulmonary gas samples and 13CO2 excretion were taken prior to fluid ingestion and at 5,10,15,30,45,60,75, and 90 min of CE, at the end of HI, and 15 min of recovery. HI after CE was 25% longer with C than G (6.5+/-0.8 vs. 5.2+/-1.0 min, P<0.05). 13CO2 from the -2 min lactate tracer was significantly elevated above rest at 5 min of exercise, and peaked at 15 min. 13CO2 from the -2 min glucose tracer peaked at 45 min for C and G. 13CO2 increased rapidly from the 45 min lactate dose, and by 60 min of exercise was 33% greater than glucose in C or G, and 36% greater than fructose in G. 13CO2 production following tracer fructose ingestion was greater than glucose in the first 45 minutes in C and G. Cumulative recoveries of tracer during exercise were: 92%+/-5.3% for lactate in C and 25+/-4.0% for glucose in C or G. Recoveries for fructose in C and G were 75+/-5.9% and 26+/-6.6%, respectively. Lactate was used more rapidly and to a greater extent than fructose or glucose. CytoMax significantly enhanced HI.