Seed persistence is the survival of seeds in the environment once they have reached maturity. Seed persistence allows a species, population or genotype to survive long after the death of parent plants, thus distributing genetic diversity through time. The ability to predict seed persistence accurately is critical to inform long-term weed management and flora rehabilitation programs, as well as to allow a greater understanding of plant community dynamics. Indeed, each of the 420000 seed-bearing plant species has a unique set of seed characteristics that determine its propensity to develop a persistent soil seed bank. The duration of seed persistence varies among species and populations, and depends on the physical and physiological characteristics of seeds and how they are affected by the biotic and abiotic environment. An integrated understanding of the ecophysiological mechanisms of seed persistence is essential if we are to improve our ability to predict how long seeds can survive in soils, both now and under future climatic conditions. In this review we present an holistic overview of the seed, species, climate, soil, and other site factors that contribute mechanistically to seed persistence, incorporating physiological, biochemical and ecological perspectives. We focus on current knowledge of the seed and species traits that influence seed longevity under ex situ controlled storage conditions, and explore how this inherent longevity is moderated by changeable biotic and abiotic conditions in situ, both before and after seeds are dispersed. We argue that the persistence of a given seed population in any environment depends on its resistance to exiting the seed bank via germination or death, and on its exposure to environmental conditions that are conducive to those fates. By synthesising knowledge of how the environment affects seeds to determine when and how they leave the soil seed bank into a resistance-exposure model, we provide a new framework for developing experimental and modelling approaches to predict how long seeds will persist in a range of environments.

Herbicides classified as synthetic auxins have been most commonly used to control broadleaf weeds in a variety of crops and in non‐cropland areas since the first synthetic auxin herbicide (SAH), 2,4‐D, was introduced to the market in the mid‐1940s. The incidence of weed species resistant to SAHs is relatively low considering their long‐term global application with 30 broadleaf, 5 grass, and 1 grass‐like weed species confirmed resistant to date. An understanding of the context and mechanisms of SAH resistance evolution can inform management practices to sustain the longevity and utility of this important class of herbicides. A symposium was convened during the 2nd Global Herbicide Resistance Challenge (May 2017; Denver, CO, USA) to provide an overview of the current state of knowledge of SAH resistance mechanisms including case studies of weed species resistant to SAHs and perspectives on mitigating resistance development in SAH‐tolerant crops. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

HighlightReduced translocation of 2,4-D confers resistance in wild radish, and is due to inhibition of phloem loading, rather than enhanced metabolism or sequestration of the herbicide.

Lupin products may be valuable as human foods because of their high protein content and potential anticholesterolemic properties. However, a small percentage of the population is allergic to lupin. In this study, we use in vitro IgE binding and mass spectrometry to identify conglutin beta, a major storage protein, as an allergen in seeds of Lupinus angustifolius and Lupinus albus. Purification of conglutin beta from L. angustifolius flour confirmed that serum IgE binds to this protein. Where IgE in sera recognized lupin proteins on Western blots, it recognized conglutin beta, suggesting this protein is a major allergen for lupin. The L. angustifolius conglutin beta allergen has been designated Lup an 1 by the International Union of Immunological Societies (IUIS) allergen nomenclature subcommittee.

BACKGROUNDMultiple‐herbicide resistance in Lolium rigidum and other weed species is increasingly exerting pressure on herbicide discovery research for solutions against resistance‐prone weeds. In this study we investigate: (i) the responses of L. rigidum populations and wheat to the new herbicide cinmethylin in comparison with other pre‐emergence herbicides, (ii) the effect of seed burial depths on cinmethylin efficacy and crop selectivity, and (iii) the basis of cinmethylin selectivity in wheat.RESULTSCinmethylin at 400 g ha−1 controls herbicide‐susceptible and multiple‐resistant L. rigidum, with a reduction of >85% in plant emergence and 90% in aboveground biomass. Cinmethylin provides effective control of a large number of field populations of L. rigidum with evident resistance to trifluralin. When the wheat seed is buried ≥1 cm below the cinmethylin‐treated soil surface, the emergence of crop seedlings is not different from the untreated control. The organophosphate insecticide phorate synergizes cinmethylin toxicity in wheat, with an LD50 of 682 g ha−1 in the absence of phorate versus 109 g ha−1 in the presence of phorate (84% reduction). The synergistic effect of phorate with cinmethylin on herbicide‐susceptible L. rigidum appears smaller (a 44% reduction in the LD50 of cinmethylin).CONCLUSIONSCinmethylin is effective in controlling multiple‐resistant L. rigidum and appears safe for wheat when the seed is separated at depth from the herbicide applied to the soil surface. The basis of this metabolism‐based selectivity is likely regulated by cytochrome P450 monooxygenases. © 2020 Society of Chemical Industry

BackgroundIn legumes, seed storage proteins are important for the developing seedling and are an important source of protein for humans and animals. Lupinus angustifolius (L.), also known as narrow-leaf lupin (NLL) is a grain legume crop that is gaining recognition as a potential human health food as the grain is high in protein and dietary fibre, gluten-free and low in fat and starch.ResultsGenes encoding the seed storage proteins of NLL were characterised by sequencing cDNA clones derived from developing seeds. Four families of seed storage proteins were identified and comprised three unique α, seven β, two γ and four δ conglutins. This study added eleven new expressed storage protein genes for the species. A comparison of the deduced amino acid sequences of NLL conglutins with those available for the storage proteins of Lupinus albus (L.), Pisum sativum (L.), Medicago truncatula (L.), Arachis hypogaea (L.) and Glycine max (L.) permitted the analysis of a phylogenetic relationships between proteins and demonstrated, in general, that the strongest conservation occurred within species. In the case of 7S globulin (β conglutins) and 2S sulphur-rich albumin (δ conglutins), the analysis suggests that gene duplication occurred after legume speciation. This contrasted with 11S globulin (α conglutin) and basic 7S (γ conglutin) sequences where some of these sequences appear to have diverged prior to speciation. The most abundant NLL conglutin family was β (56%), followed by α (24%), δ (15%) and γ (6%) and the transcript levels of these genes increased 103 to 106 fold during seed development. We used the 16 NLL conglutin sequences identified here to determine that for individuals specifically allergic to lupin, all seven members of the β conglutin family were potential allergens.ConclusionThis study has characterised 16 seed storage protein genes in NLL including 11 newly-identified members. It has helped lay the foundation for efforts to use molecular breeding approaches to improve lupins, for example by reducing allergens or increasing the expression of specific seed storage protein(s) with desirable nutritional properties.

Synthetic herbicides have been used globally to control weeds in major field crops. This has imposed a strong selection for any trait that enables plant populations to survive and reproduce in the presence of the herbicide. Herbicide resistance in weeds must be minimized because it is a major limiting factor to food security in global agriculture. This represents a huge challenge that will require great research efforts to develop control strategies as alternatives to the dominant and almost exclusive practice of weed control by herbicides. Weed scientists, plant ecologists and evolutionary biologists should join forces and work towards an improved and more integrated understanding of resistance across all scales. This approach will likely facilitate the design of innovative solutions to the global herbicide resistance challenge.

High-intensity cropping systems are likely to impose greater selection pressures for seed dormancy and selective herbicide resistance, because late-emerging seedlings avoid preplanting weed control practices (tillage and non-selective herbicide application) but are exposed to selective in-crop herbicides.