This study investigated whether kelp extract from Durvillaea potatorum and Ascophyllum nodosum (Seasol Commercial^®) stimulates broccoli establishment and growth. Under controlled conditions in the glasshouse, weekly applications of kelp extract significantly increased the leaf area, stem diameter and biomass of broccoli by up to 70%, 65% and 145%, respectively. Also in the glasshouse, lower strength dilutions of kelp extract (1:200 to 1:500) were most effective in stimulating early growth of broccoli, whereas higher strength dilutions (1:25 to 1:100) were most effective later in plant development. In the field, application of kelp extract as a drench to a clay-loam soil (Sodosol) significantly increased the leaf number, stem diameter and leaf area of establishing broccoli seedlings by 6%, 10% and 9%, respectively, irrespective of application rate (three applications at 2.5 or 25 l ha^− 1). Furthermore, kelp extract significantly reduced the early incidence of white blister, caused by Albugo candida, on broccoli by 23%. In a sandy soil (Podosol), the effect of kelp extract was less pronounced, with only the leaf area of broccoli seedlings increasing significantly following treatment with kelp applied at the highest rate. It is hypothesized that differences in cation exchange capacity, organic matter and/or leaching properties contribute to variation in the response of broccoli to kelp extract in different soils. Future research is proposed to examine the capacity of kelp extract to offset the high nutrient inputs needed at establishment in the broccoli industry.

A sand solution technique demonstrated the capacity for a commercial seaweed extract from Durvillaea potatorum and Ascophyllum nodosum (Seasol Commercial®) to significantly suppress infection of broccoli by Plasmodiophora brassicae. In the primary stages of infection, the extract reduced the number of plasmodia formed in the root hairs by 55 %. Later, in the secondary stages of infection, the extract reduced plasmodia in the root cortical cells by up to 84 %. The suppression of infection was found to be independent of the dilution of the extract applied (1:25 and 1:500). The basis for these results is unlikely to be a nutrient or pH effect since the extract had little impact on these parameters, particularly at the lower dilution (1:200). Rather, we hypothesise that the suppression of infection by the seaweed extract was due to its stimulation of resistance mechanisms in the host, which is possibly related to laminarins in the extract and/or the effect of exogenous growth regulators or undiscovered molecules in the extract disrupting the infection process.

Strawberry is an important horticultural crop in Victoria, Australia. Grey mould caused by Botrytis cinerea reduces marketable yield and post-harvest quality of strawberry fruit in the region. We conducted two field experiments in Victoria (Coldstream and Warburton) to evaluate the effectiveness of a commercial seaweed extract from Durvillaea potatorum and Ascophyllum nodosum (Seasol®) on the yield, revenue, and post-harvest rot of strawberry fruit. We applied the extract to strawberry crops (cv. Albion) monthly as a combined drench (10 L ha^-1) and foliar spray (1:400), with water as a control. Application of the seaweed extract significantly increased strawberry fruit yields by 8-10% and revenue by AU$0.37-0.59 per plant. Furthermore, the extract significantly reduced the incidence and severity of post-harvest rots in strawberry fruit by 52-87%, respectively. The extract did not affect the firmness, soluble solids concentration (SSC), titratable acidity, or SSC:acid of strawberry fruit. In a separate laboratory experiment, we found that growing strawberry in the seaweed extract (1:400) increased the concentration of peroxidase by 50% and doubled H₂O₂ in roots soon after treatment. Increases in reactive oxygen species are an indicator of a suite of pathways associated with resistance and tolerance of biotic and abiotic stresses. Overall, the results demonstrate that the seaweed extract can act as a commercially-viable biostimulant for strawberry fruit production in south-eastern Australia.

The pursuit of sustainable and productive agriculture demands the exploration of innovative approaches to improve plant productivity and soil health. The utilization of natural agricultural biostimulants, such as extracts from seaweed, fish, and humus, has gained prominence as an ecological strategy to achieve this goal. In this study we investigated the effectiveness of a fortified biostimulant extract (FBE), composed of extracts from seaweed, fish, and humus, on tomato plant physiology, productivity, and growing media properties, and estimated carbon emissions associated with tomato production. The FBE was applied to the growing media of tomato plants produced in a greenhouse, in experiments over two growing seasons. The productivity assessments demonstrated that the application of FBE significantly increased tomato fruit yield by 20% and relative marketable fruit yield by 27%, and reduced estimated greenhouse gas (GHG) emissions associated with production by 29%. FBE treatment improved plant shoot and root biomass, accelerated flower and fruit set initiation, and increased chlorophyll content in leaves, resulting in enhanced plant physiology and advanced development. FBE treatment positively influenced the availability of crucial nutrients such as nitrogen, phosphorus, and iron in the growing media. FBE promoted the growth of total active microbes in the growing media, particularly the fungal population, which plays an important role in nutrient cycling and health. These findings highlight the beneficial effects of the FBE due to enhanced plant productivity and growth, improved fertility, the promotion of beneficial plant and growing media interactions, and the reduction in estimated GHG emissions.

Knowledge of the factors structuring populations of pathogenic fungi is fundamental to disease management efforts and basic biology. However, this crucial information is missing for many important pathogens, including broad-host-range and drought-associated pathogens from the globally distributed Macrophomina genus. The objectives of this work were to evaluate the evidence for host specialization, geographic adaptation, and recombination using a global survey of Macrophomina isolates from diverse geographic, temporal, and host sources. We obtained high-quality short-read sequence data for 463 Macrophomina spp. isolates, representing four putative species, collected from 91 host plant species and soil in 23 countries. Analysis of bi-allelic, single-nucleotide polymorphisms revealed high diversity, admixture, and equal mating type ratios, suggesting ongoing recombination. Although most tested isolates asymptomatically colonized strawberry, only strawberry-derived isolates caused disease on this host. These isolates were all in a single lineage, suggesting that the ability to cause disease on strawberry is not widespread among M. phaseolina. Significant associations were also found between isolations from soybean plants and specific population clusters, suggesting that specialization for virulence or reproduction has also occurred for soybean. Geography × isolate genotype associations were weak, suggesting that Macrophomina spp. were frequently trafficked between regions. Reference-free whole-genome comparisons support current boundaries among four Macrophomina species, and new molecular markers were designed to specifically identify each species. Contrary to expectations, M. phaseolina should be considered a single species with both specialist and generalist populations in which meiosis can maintain genetic diversity. [ ] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .