A new protocol for speed vernalisation of winter cereals

There are many challenges facing the development of high-yielding, nutritious crops for future environments. One limiting factor is generation time, which prolongs research and plant breeding timelines. Recent advances in speed breeding protocols have dramatically reduced generation time for many short-day and long-day species by optimising light and temperature conditions during plant growth. However, winter crops with a vernalisation requirement still require up to 6–10 weeks in low-temperature conditions before transition to reproductive development. Here, we tested a suite of environmental conditions and protocols to investigate if vernalisation can be satisfied more efficiently. We identified a vernalisation method consisting of exposing seeds at the soil surface to an extended photoperiod of 22 h day:2 h night at 10°C with transfer to speed breeding conditions that dramatically reduces generation time in both winter wheat (Triticum aestivum) and winter barley (Hordeum vulgare). Implementation of this protocol achieved up to five generations per year for winter wheat or barley, instead of the two typically obtained under standard vernalisation and plant growth conditions. The protocol has great potential to enhance training and to accelerate research, pre-breeding, and breeding outcomes focussed on winter crop improvement.

A Trimethylguanosine Synthase1-like (TGS1) homologue is implicated in vernalisation and flowering time control

Key message A plant-specificTrimethylguanosine Synthase1-likehomologue was identified as a candidate gene for theeflmutation in narrow-leafed lupin, which alters phenology by reducing vernalisation requirement. Abstract The vernalisation pathway is a key component of flowering time control in plants from temperate regions but is not well understood in the legume family. Here we examined vernalisation control in the temperate grain legume species, narrow-leafed lupin (Lupinus angustifolius L.), and discovered a candidate gene for an ethylene imine mutation (efl). The efl mutation changes phenology from late to mid-season flowering and additionally causes transformation from obligate to facultative vernalisation requirement. The efl locus was mapped to pseudochromosome NLL-10 in a recombinant inbred line (RIL) mapping population developed by accelerated single seed descent. Candidate genes were identified in the reference genome, and a diverse panel of narrow-leafed lupins was screened to validate mutations specific to accessions with efl. A non-synonymous SNP mutation within an S-adenosyl-L-methionine-dependent methyltransferase protein domain of a Trimethylguanosine Synthase1-like (TGS1) orthologue was identified as the candidate mutation giving rise to efl. This mutation caused substitution of an amino acid within an established motif at a position that is otherwise highly conserved in several plant families and was perfectly correlated with the efl phenotype in F2 and F6 genetic population and a panel of diverse accessions, including the original efl mutant. Expression of the TGS1 homologue did not differ between wild-type and efl genotypes, supporting altered functional activity of the gene product. This is the first time a TGS1 orthologue has been associated with vernalisation response and flowering time control in any plant species.

COR/LEA Proteins as Indicators of Frost Tolerance in Triticeae: A Comparison of Controlled versus Field Conditions

Low temperatures in the autumn induce enhanced expression/relative accumulation of several cold-inducible transcripts/proteins with protective functions from Late-embryogenesis-abundant (LEA) superfamily including dehydrins. Several studies dealing with plants grown under controlled conditions revealed a correlation (significant quantitative relationship) between dehydrin transcript/protein relative accumulation and plant frost tolerance. However, to apply these results in breeding, field experiments are necessary. The aim of the review is to provide a summary of the studies dealing with the relationships between plant acquired frost tolerance and COR/LEA transcripts/proteins relative accumulation in cereals grown in controlled and field conditions. The impacts of cold acclimation and vernalisation processes on the ability of winter-type Triticeae to accumulate COR/LEA proteins are discussed. The factors determining dehydrin relative accumulation under controlled cold acclimation treatments versus field trials during winter seasons are discussed. In conclusion, it can be stated that dehydrins could be used as suitable indicators of winter survival in field-grown winter cereals but only in plant prior to the fulfilment of vernalisation requirement.

Evaluation of currently registered herbicides for fall bearing year red sorrel (Rumex acetosella L.) management in lowbush blueberry (Vaccinium angustifolium Ait.)

Red sorrel is a common creeping herbaceous perennial weed species in lowbush blueberry fields and reproduces asexually via ramets from creeping roots. Ramets emerge throughout the season but remain vegetative due to a vernalisation requirement for flowering. This weed may therefore be managed with fall herbicide applications, but few currently registered herbicides have been evaluated for fall red sorrel management in lowbush blueberry. The objectives of this research were to 1) determine the effect of various herbicide treatments on red sorrel shoot and root biomass in the greenhouse, 2) determine the effect of fall bearing year herbicide applications on overwintered red sorrel ramet density in the field, 3) determine if reduced overwintered ramet density reduces flowering ramet density in the field, and 4) estimate the potential for red sorrel to recover from fall bearing year herbicide applications. Dicamba, tribenuron-methyl, and glufosinate reduced red sorrel shoot and root biomass in the greenhouse and reduced overwintered ramet density in the field. Clopyralid, sulfentrazone, and flumioxazin reduced shoot and root biomass in the greenhouse but exhibited limited efficacy in the field. Nicosulfuron+rimsulfuron and glyphosate were ineffective in both the greenhouse and field. Dichlobenil and pronamide reduced overwintered ramet density in the field. Reduction of overwintered ramet density did not consistently reduce flowering ramet density. Dichlobenil reduced seedling density at two sites, but no herbicide consistently reduced summer non-bearing year ramet density. Fall herbicide applications alone therefore do not appear to maintain red sorrel suppression in lowbush blueberry fields.

The vernalisation regulator FLOWERING LOCUS C is differentially expressed in biennial and annual Brassica napus

Plants in temperate areas evolved vernalisation requirement to avoid pre-winter flowering. In Brassicaceae, a period of extended cold reduces the expression of the flowering inhibitor FLOWERING LOCUS C (FLC) and paves the way for the expression of downstream flowering regulators. As with all polyploid species of the Brassicaceae, the model allotetraploid Brassica napus (rapeseed, canola) is highly duplicated and carries 9 annotated copies of Bna.FLC. To investigate whether these multiple homeologs and paralogs have retained their original function in vernalisation or undergone subfunctionalisation, we compared the expression patterns of all 9 copies between vernalisation-dependent (biennial, winter type) and vernalisation-independent (annual, spring type) accessions, using RT-qPCR with copy-specific primers and RNAseq data from a diversity set. Our results show that only 3 copies – Bna.FLC.A03b, Bna.FLC.A10 and to some extent Bna.FLC.C02 – are differentially expressed between the two growth types, showing that expression of the other 6 copies does not correlate with growth type. One of those 6 copies, Bna.FLC.C03b, was not expressed at all, indicating a pseudogene, while three further copies, Bna.FLC.C03a and Bna.FLC.C09ab, did not respond to cold treatment. Sequence variation at the COOLAIR binding site of Bna.FLC.A10 was found to explain most of the variation in gene expression. However, we also found that Bna.FLC.A10 expression is not fully predictive of growth type.

Winter wheat cultivars in Australian farming systems: a review

Winter wheat cultivars are defined as those that have an obligate vernalisation requirement that must be met before they will progress from the vegetative to reproductive phase of development i.e. they must experience a true winter before they will flower. Historically, very little breeding effort has been applied to the selection of winter cultivars suited to southern Australia, with the notable exception of the New South Wales Agriculture breeding program based in Wagga and Temora that ran from the 1960s until 2002. A shift by growers to earlier sowing, increased usage of dual-purpose cereals, and research highlighting the whole-farm benefits of winter cultivars to average farm wheat yield has increased grower interest and demand for winter cultivars. Three major wheat breeding companies operating in southern Australia have responded by commencing selection for milling quality winter cultivars, the first of which was released in 2017. Existing research relating to winter wheats in southern Australian farming systems is reviewed here, including interactions with agronomic management, environment and weeds and disease. It is concluded that winter wheats can offer significant production and farming system benefits to growers by allowing earlier establishment, which increases water-limited potential yield (PYw) by ~15% relative to later sown spring wheats, and makes forage available for dual-purpose grazing during vegetative development. Winter wheats sown early require agronomic management different to that of later sown spring wheats, including greater attention to control of grass weeds and certain diseases. There are significant research gaps that will prevent growers from maximising the opportunities from new winter cultivars once they are released. The first of these is a well-defined establishment window for winter cultivars, particularly in medium-low rainfall environments of South Australia, Victoria and Western Australia that have not historically grown them. There is circumstantial evidence that the yield advantage of early established winter wheats over later sown spring wheats is greatest when stored soil water is present at establishment, or the soil profile fills during the growing season. Explicit confirmation of this would allow growers to identify situations where the yield advantage of winter wheats will be maximised. Given the imminent release of several new winter wheat cultivars and the increases in PYw that they embody, it is critical to experimentally define the management and environmental conditions under which performance of these new genotypes are optimised, before their release and availability to growers. Optimising the genotype × environmental × management interactions possible with these cultivars will empower growers to make the best use of the technology and better realise the gains in water limited potential yield possible with these genotypes.

Optimising grain yield and grazing potential of crops across Australia’s high-rainfall zone: a simulation analysis. 2. Canola

Recent expansion of cropping into Australia’s high-rainfall zone (HRZ) has involved dual-purpose crops suited to long growing seasons that produce both forage and grain. Early adoption of dual-purpose cropping involved cereals; however, dual-purpose canola (Brassica napus) can provide grazing and grain and a break crop for cereals and grass-based pastures. Grain yield and grazing potential of canola (up until bud-visible stage) were simulated, using APSIM, for four canola cultivars at 13 locations across Australia’s HRZ over 50 years. The influence of sowing date (2-weekly sowing dates from early March to late June), nitrogen (N) availability at sowing (50, 150 and 250 kg N/ha), and crop density (20, 40, 60, 80 plants/m2) on forage and grain production was explored in a factorial combination with the four canola cultivars. The cultivars represented winter, winter × spring intermediate, slow spring, and fast spring cultivars, which differed in response to vernalisation and photoperiod. Overall, there was significant potential for dual-purpose use of winter and winter × spring cultivars in all regions across Australia’s HRZ. Mean simulated potential yields exceeded 4.0 t/ha at most locations, with highest mean simulated grain yields (4.5–5.0 t/ha) in southern Victoria and lower yields (3.3–4.0 t/ha) in central and northern New South Wales. Winter cultivars sown early (March–mid-April) provided most forage (>2000 dry sheep equivalent (DSE) grazing days/ha) at most locations because of the extended vegetative stage linked to the high vernalisation requirement. At locations with Mediterranean climates, the low frequency (<30% of years) of early sowing opportunities before mid-April limited the utility of winter cultivars. Winter × spring cultivars (not yet commercially available), which have an intermediate phenology, had a longer, more reliable sowing window, high grazing potential (up to 1800 DSE-days/ha) and high grain-yield potential. Spring cultivars provided less, but had commercially useful grazing opportunities (300–700 DSE-days/ha) and similar yields to early-sown cultivars. Significant unrealised potential for dual-purpose canola crops of winter × spring and slow spring cultivars was suggested in the south-west of Western Australia, on the Northern Tablelands and Slopes of New South Wales and in southern Queensland. The simulations emphasised the importance of early sowing, adequate N supply and sowing density to maximise grazing potential from dual-purpose crops.

Effect of timing and height of defoliation on the grain yield of barley, wheat, oats and canola in Western Australia

Winter cropping in Western Australia (WA) is dominated by spring-type cereals and canola (Brassica napus L.) with no vernalisation requirement that are sown in late autumn (late April and May). With limited earlier sowing opportunities for later maturing winter-type crops in early autumn, farmers aiming to obtain some benefit from the grazing of crops (i.e. dual-purpose) must consider the grazing potential of spring types sown in late autumn. The aim of this study was to develop grazing guidelines for spring-type crops in WA that will limit the potential for grain yield losses. In order to determine the recovery response of spring-type crops to grazing intensity and timing, 59 time-of-cutting × height-of-cutting experiments were conducted throughout the south-western region of WA in 2012. Experiments were conducted on spring types of wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), canola and oats (Avena sativa L.). Multi-site analysis showed that treatments simulating high-intensity ‘crash’ grazing to ground level or to a height of 5 cm reduced grain yield unless conducted early in vegetative growth before reproductive stages. Treatments simulating ‘clip’ grazing by removing only the top 5–10 cm of crop foliage reduced grain yield to a lesser extent than crash grazing, and in several instances could extend the safe cutting period past hollow stem (Zadoks growth stage 30) and/or the end of July for cereals, or past mid-July for spring canola, provided the developing reproductive parts of all crops were not damaged. On average, the amounts of biomass removed by clip grazing without yield penalty were 0.4, 0.3, 0.5 and 0.3 t ha–1 for barley, wheat, oats and canola and were similar to those removed by earlier, safe crash grazing. These represent significant amounts of forage and suggest that clip grazing of spring-type crops may be an approach suited to WA cropping and grazing systems.

Effect of chromosome 3B gene/s of Česká Přesívka on vernalisation response, photoperiod sensitivity and earliness of wheat

Substitution lines with the chromosome 3B of the Czech alternative cultivar&nbsp;Česk&aacute; Přes&iacute;vka (CP) in the genetic&nbsp;background of the wheat cultivars Zdar, Vala, Ko&scaron;utka, Jara and Sandra, differing in their requirements of vernalisation and photoperiod, were compared with the original cultivars under short and long photoperiod, to evaluate the effects of genes, located on the chromosome 3B of CP, on earliness and the response to photoperiod and vernalisation. The results suggest that these genes have only a small effect upon the vernalisation requirement, but are more related to the response to photoperiod. However, the genes on the substituted chromosome appear to influence the earliness per se and very likely interact also with the photoperiodic response. &nbsp;