Biology subjects

Abu-Nassar, J.

Publications and source records attributed to Abu-Nassar, J..

3 recordsLinked to original sources

bioRxiv2026

First case of three-way multiple herbicide resistance in Amaranthus palmeri outside the Americas: Resistance mechanisms and alternative management strategies

The rapid spread of herbicide-resistant Amaranthus palmeri S. Watson across the Mediterranean region poses a severe threat to crop production. This study characterizes the resistance profile of an A. palmeri population from Gonen, Israel, which survived multiple post-emergence herbicide applications in maize. Greenhouse dose-response and screening trials were conducted across four modes of action (MOAs). The Gonen population exhibited three-way multiple resistance to acetolactate synthase (ALS), photosystem II (PSII) and 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitors, marking the first confirmed case outside the Americas. High-level resistance was demonstrated for the ALS inhibitor foramsulfuron and the PSII inhibitor metribuzin, maintaining 40-70% and 80-100% survival, respectively, at double the labelled field rate. Sequencing of the ALS gene revealed a Trp574 to Leu substitution in resistant plants. The population showed differential PSII sensitivity, as atrazine provided complete control despite high metribuzin survival. Sequencing revealed no known psbA mutations, and malathion pre-treatment caused only a slight reduction in metribuzin survival. Partial resistance was observed for the HPPD inhibitor tembotrione (30-50% survival), where malathion pre-treatment reduced survival by 20-30%. In contrast, pre-mergence applications of S-metolachlor (very long chain fatty acid inhibitor), isoxaflutole (HPPD inhibitor), and a fomesafen + terbutryn mixture [protoporphyrinogen oxidase (PPO) + PSII inhibitors] significantly reduced emergence. These findings confirm multiple-resistant A. palmeri in the region and highlight the urgent need for integrated weed management incorporating effective pre-emergence herbicides rather than relying solely on post-emergence chemical control in summer cereal rotations.

plant biology↗

bioRxiv2026

Warming and resource enrichment decouple growth from enzymatic investment, shifting the competitive balance between native and invasive plants

Invasive plants can reshape ecosystems by altering soil biogeochemistry and microbial functioning under global change. Competitive interactions between the invasive Conyza bonariensis and the native Helminthotheca echioides were evaluated under warming, nitrogen enrichment, and elevated CO2, together with rhizosphere microbial function in solitary versus competitive growth. Plants were grown alone or in interspecific competition under elevated temperature (27 vs 29 {degrees}C), ammonium-nitrate fertilization versus no fertilization, and ambient versus elevated CO2 (400 vs 720 ppm). Plant traits and relative growth rate (RGR) were measured alongside potential extracellular enzyme activities (EEA) of -D-glucosidase (C acquisition) and N-acetyl-{beta}-D-glucosaminidase (NAGase; N acquisition) and functional gene abundances (nirS and bacterial amoA). To relate enzyme signals to plant demand and microbial biomass, we calculated a growth-normalized rhizosphere investment metric (Specific Rhizosphere Index; SRI) and a biomass-normalized investment metric (Specific Enzyme Activity; SEA). Competition effects were summarized as {Delta}SRI and {Delta}Tax (change from alone to competition) to quantify how competition altered growth- and biomass-normalized investment. Plant responses were driver- and context-dependent. Elevated CO2 produced the largest changes in growth traits, especially for the invasive species. Warming effects were modest in solitary plants but became apparent under competition, where elevated temperature reduced competitive suppression via increased invasive leaf production and reduced constraints on native leaf expansion. Fertilization caused comparatively small shifts in plant endpoints. Microbial responses depended strongly on soil conditioning history. Potential EEA showed limited shifts with warming and fertilization, whereas elevated CO2 enhanced NAGase mainly in invasive-conditioned soils and increased nirS across soils. Despite overlap in ecoenzymatic stoichiometry, SRI and {Delta}Tax revealed treatment- and legacy-dependent patterns in how competition re-scaled microbial C and N acquisition relative to plant growth and microbial biomass. Together, these results indicate that global change can decouple plant growth from enzymatic investment and reconfigure invasive-native interactions through shifts in above-belowground coupling.

microbiology↗

bioRxiv2023

Occurrence of Amaranthus palmeri in Israeli agriculture: status of spread and response to glyphosate and trifloxysulfuron

Amaranthus palmeri S. Watson is a dioecious annual weed species, originating from the Southern USA, spreading rapidly beyond its original range into Europe and the Mediterranean region. In Israel, A. palmeri distribution has expanded quickly in recent years, with farmers reporting on weed control failure using acetolactate synthase (ALS) inhibitors. Furthermore, recent studies have documented glyphosate-resistant cases from other countries in the region, such as Spain, Greece, and Turkey. We conducted a survey in order to understand A. palmeri distribution and study the occurrence of herbicide resistance to both glyphosate and trifloxysulfuron in different fields across the country. According to our data, A. palmeri population locations are aligned with the major agricultural areas for summer field crops, including the Hula Valley, Jezreel Valley, and the Southern Coastal Plain. Regarding herbicide responses, while several populations showed a reduced response to glyphosate, dose-response assays did not show resistance to the recommended labeled field rate. For the ALS inhibitor trifloxysulfuron, the proportion of resistant individuals was very high, especially in the southern coastline region, with an R-value of 0.77. Four populations used for dose-response studies were highly resistant, surviving at four times the recommended labeled field rate of trifloxysulfuron (30 g a.i. ha-1). Sequencing of the ALS gene, Trp574 to Leu alteration in resistant populations was recorded. The high level of resistance observed in this study, alongside the target-site mutation found in populations of A. palmeri, endangers the future use of ALS inhibitors in corn, cotton, and other summer crops grown in Israel.

plant biology↗