Tissue culture tools for selenium hyperaccumulator Neptunia amplexicaulis for development in phytoextraction

Neptunia amplexicaulis is an herbaceous legume endemic to the Richmond area in central Queensland,Australia and is one of the strongest known Selenium hyperaccumulators on earth,showing significant potential to be utilised in Se phytoextraction applications.Here a protocol was established for in vitro micropropagation of Se hyperaccumula-tor N.amplexicaulis using nodal segments from in vitro-germinated seedlings.Shoot multiplication was achieved on Murashige and Skoog(MS)basal media supplemented with various concentrations of 6-Benzylaminopurine(BA)(1.0,2.0,3.0 mg L^(−1))alone or in combination with low levels of Naphthaleneacetic acid(NAA)(0.1,0.2,0.3 mg L^(−1)),with 2.0 mg L^(−1) BA+0.2 mg L^(−1) NAA found to be most effective.Elongated shoots were rooted in vitro using NAA,with highest root induction rate of 30%observed at 0.2 mg L^(−1) NAA.About 95%of the in vitro rooted shoots survived acclimatization.Clonally propagated plantlets were dosed with selenate/selenite solution and assessed for Se tissue concentrations using Inductively Coupled Plasma Atomic Emission Spectroscopy(ICP-AES)and found to retain their ability to hyperaccumulate.The protocol developed for this study has potential to be optimised for generating clonal plants of N.amplexicaulis for use in research and phytoextraction industry applications.

Perennial grass and herb options to extend summer–autumn forage in a drought-prone temperate environment

Background:The ability to finish livestock on pasture over the summer–autumn period could improve the profitability of red meat enterprises in drought-prone temperate regions.In south-eastern Australia,traditional perennial options are limited by poor warm-season performance(phalaris,Phalaris aquatica L.)and widespread environmental constraints(lucerne,Medicago sativa L.).We aimed to identify perennial species suitable for summer–autumn finishing.Methods:We tested pure swards of summer-active perennial grasses and herbs(20 cultivars across 14 species)in replicated small-plot experiments at two sites on the Southern Tablelands of New South Wales,Australia.We assessed early persistence,productivity and warm-season nutritive characteristics over 2–3 years.Results:Lucerne and chicory(Cichorium intybus L.)persisted well through drought and produced herbage of high quantity and quality through summer–autumn.Digit grass(Digitaria eriantha Steud.)was highly persistent and productive but nutritive values were generally poor.Cocksfoot(Dactylis glomerata L.),tall fescue(Festuca arundinacea Schreb.),perennial ryegrass(Lolium perenne L.),prairie grass(Bromus willdenowii Kunth.)and plantain(Plantago lanceolata L.)were productive but less persistent through drought,while nutritive values were sometimes inadequate.Conclusions:Chicory is a good alternative to lucerne,given its excellent summer–autumn performance,ability to survive droughts and superior acid soil tolerance.If appropriate management resolves issues with persistence and nutritive value,several of the other species could also be used to close the warm-season feed gap in drought-prone temperate environments.

Perspectives on plant virus diseases in a climate change scenario of elevated temperatures

Global food production is at risk from many abiotic and biotic stresses and can be affected by multiple stresses simultaneously.Virus diseases damage cultivated plants and decrease the marketable quality of produce.Importantly,the progression of virus diseases is strongly affected by changing climate conditions.Among climate-changing vari-ables,temperature increase is viewed as an important factor that affects virus epidemics,which may in turn require more efficient disease management.In this review,we discuss the effect of elevated temperature on virus epidem-ics at both macro-and micro-climatic levels.This includes the temperature effects on virus spread both within and between host plants.Furthermore,we focus on the involvement of molecular mechanisms associated with tempera-ture effects on plant defence to viruses in both susceptible and resistant plants.Considering various mechanisms proposed in different pathosystems,we also offer a view of the possible opportunities provided by RNA-based technologies for virus control at elevated temperatures.Recently,the potential of these technologies for topical field applications has been strengthened through a combination of genetically modified(GM)-free delivery nanoplat-forms.This approach represents a promising and important climate-resilient substitute to conventional strategies for managing plant virus diseases under global warming scenarios.In this context,we discuss the knowledge gaps in the research of temperature effects on plant-virus interactions and limitations of RNA-based emerging technologies,which should be addressed in future studies.

BioClay^(TM)prolongs RNA interference-mediated crop protection against Botrytis cinerea

One of the most promising tools for the control of fungal plant diseases is spray-induced gene silencing(SIGS).In SIGS,small interfering RNA(siRNA)or double-stranded RNA(dsRNA)targeting essential or virulence-related pathogen genes are exogenously applied to plants and postharvest products to trigger RNA interference(RNAi)of the targeted genes,inhibiting fungal growth and disease.However,SIGS is limited by the unstable nature of RNA under environmental conditions.The use of layered double hydroxide or clay particles as carriers to deliver biologically active dsRNA,a formulation termed BioClay^(TM),can enhance RNA durability on plants,prolonging its activity against pathogens.Here,we demonstrate that dsRNA delivered as BioClay can prolong protection against Botrytis cinerea,a major plant fungal pathogen,on tomato leaves and fruit and on mature chickpea plants.BioClay increased the protection window from 1 to 3 weeks on tomato leaves and from 5 to 10 days on tomato fruits,when compared with naked dsRNA.In flowering chickpea plants,BioClay provided prolonged protection for up to 4 weeks,covering the critical period of poding,whereas naked dsRNA provided limited protection.This research represents a major step forward for the adoption of SIGS as an eco-friendly alternative to traditional fungicides.