Biology subjects

Matzrafi, M.

Publications and source records attributed to Matzrafi, M..

8 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

Invasive plant soil legacies shape microbial function and community organization under short-term carbon and nitrogen amendments

Plant invasion can modify soil microbial communities and ecosystem processes through plant-soil feedbacks, yet it remains unclear whether these effects are expressed mainly through taxonomic turnover or through shifts in microbial function and interaction structure. We tested how soil legacy generated by the invasive Conyza bonariensis, the native Helminthotheca echioides, or unplanted control soil influenced short-term microbial responses to standardized amendments and plant-derived inputs. In Experiment 1, conditioned soils were amended with water, cellulose, or ammonium and analyzed for extracellular enzyme activity, qPCR-based gene abundance, bacterial community composition, and family-level co-occurrence networks. In Experiment 2, the same soil legacies were exposed to water, glucose, or sterile root exudates from native or invasive plants. Native- and invasive-conditioned soils differed significantly in composition, but they were not consistently distinguished by strong indicator taxa, indicating that legacy effects were expressed mainly through redistribution of shared taxa rather than community turnover. In contrast, functional responses were clearer: enzyme activity and nirS abundance showed strong soil-legacy dependence, and network analysis revealed that invasive-conditioned soil supported a denser, more positive, and more compact family-level association structure than native-conditioned soil. In Experiment 2, invasive root exudates produced stronger short-term functional-based differentiation among soil legacies than native exudates, especially for extracellular enzymes. Together, the two experiments show that plant invasion can leave a persistent belowground legacy that is expressed primarily through functional filtering and network rewiring of a broadly shared microbiome, rather than through major taxonomic turnover alone.

microbiology↗

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↗

bioRxiv2026

Rainfall legacy effects on the rhizosphere bacterial diversity of Brachypodium ecotypes across an aridity gradient

Plants exhibit clinal trait variation along aridity gradients driven by strong selective pressures, yet whether plant-microbiome associations follow similar patterns remains unclear. Brachypodium spp., a model for temperate cereals spanning environments from hyper-arid to humid, provides an ideal system to test this hypothesis. Here, we compare rhizosphere bacterial communities of Brachypodium growing across arid, semi-arid, and dry sub-humid zones in Israel with those of ecotypes collected along the same precipitation gradient and grown under common-garden conditions. Rhizosphere bacterial diversity was highest in plants from mid-precipitation sites within the Mediterranean semi-arid transition zone, where annual precipitation decreases from 600 to 400 mm. Together with higher stochasticity and fewer significantly associated taxa in rhizosphere microbiomes from mid-precipitation plants suggest weaker plant-driven microbiome selection in this transition zone, a pattern that persisted under common-garden conditions. The results may represent a promising avenue to develop microbiome-based strategies for drought resilience by advancing our understanding of host filtering across aridity gradients.

ecology↗

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↗

bioRxiv2020

Recurrent selection with glufosinate at low rates reduces the susceptibility of a Lolium perenne ssp. multiflorum population to glufosinate

ABSTRACTRepeated applications of herbicides at the labelled rates have often resulted in the selection and evolution of herbicide-resistant weeds capable of surviving the labelled and higher rates in subsequent generations. However, the evolutionary outcomes of recurrent herbicide selection at low rates are far less understood. In this study of an herbicide-susceptible population of Lolium perenne ssp. multiflorum, we assessed the potential for low glufosinate rates to select for reduced susceptibility to the herbicide, and cross-resistance to herbicides with other modes of action. Reduced susceptibility to glufosinate was detected in progeny in comparison with the parental population following three rounds of selection at low glufosinate rates. Differences were mainly observed at the 0.5X, 0.75X, and 1X rates. Comparing the parental susceptible population and progeny from the second and third selection cycle, the percentage of surviving plants increased to values of LD50 (1.31 and 1.16, respectively) and LD90 (1.36 and 1.26, respectively). When treated with three alternative herbicides (glyphosate, paraquat, and sethoxydim), no plants of either the parental or successive progeny populations survived treatment with 0.75X or higher rates of these herbicides. The results of this study provide clear evidence that reduced susceptibility to glufosinate can evolve in weed populations following repeated applications of glufosinate at low herbicide rates. However, the magnitude of increases in resistance levels over three generations of recurrent low-rate glufosinate selection observed is relatively low compared with higher levels of resistance observed in response to low-rate selection with other herbicides (three fold and more).Competing Interest StatementThe authors have declared no competing interest.View Full Text

plant biology↗

bioRxiv2020

Male linked genomic regions determine sex in dioecious Amaranthus palmeri

Dioecy, the separation of reproductive organs on different individuals, has evolved repeatedly in different plant families. Several evolutionary paths to dioecy have been suggested, but the mechanisms behind sex determination is not well understood. The diploid dioecious Amaranthus palmeri represents a well suited model system to study sex determination in plants. A. palmeri is one of the most troublesome weeds in the US, has successfully colonized other regions in the world and has evolved resistance to several herbicide classes. Despite the agricultural importance of the species, the genetic control and evolutionary state of dioecy in A. palmeri is currently unknown. Early cytogenetic experiments did not identify heteromorphic chromosomes. Here, we used whole genome sequencing of male and female pools from two independent populations to elucidate the genetic control of dioecy in A. palmeri. Read alignment to a close monoecious relative and allele frequency comparisons between male and female pools did not reveal significant sex linked genes. Consequently, we employed an alignment free k-mer comparison which enabled us to identify a large number of male specific k-mers. We assembled male specific contigs comprising a total of almost 2 Mb sequence, proposing a XY sex determination system in the species. Based on our findings we suggest an intermediate evolutionary state of dioecy in A. palmeri. Our findings give insight into the evolution of sex chromosomes in plants and may help to develop sustainable strategies for weed management.

plant biology↗

bioRxiv2019

Sex Lability and Dimorphism in Diecious Palmer Amaranth (Amaranthus palmeri)

Dioecious weeds (separate sexes) may benefit from a maximized outcrossing and optimal sex-specific resource allocation but there are costs associated with the evolution of this breeding system which can be exploited for long-term management of dioecious weeds. That is, seed production in dioecious species is contingent upon the co-occurrence and co-flowering of the two genders and can be further complicated by biases in sex ratio. We therefore explored the sex ratio and dimorphism in secondary sex characters in three populations of Palmer amaranth (Amaranthus palmeri) from California, Kansas and Texas and tested if water stress can change the sex expression and/or the synchrony of flowering (anthesis) between male and female plants. Sex ratio (proportion of males) was balanced and did not deviate from 1:1 in all experiments and populations (California, Kansas, Texas) when plants received normal watering. Male and female plants of A. palmeri did not differ in timing of emergence, plant height and relative growth rate. While the initiation of flowering (emergence of inflorescence) occurred earlier in males than females, females preceded males in timing of anthesis. Water stress delayed anthesis in males to a larger extent than females giving rise to an anthesis mismatch as large as seven days between the two sexes. Water stress induced a female sex expression in Kansas population giving rise to a female to male ratio of 1.78 which significantly differed from the equal 1:1 sex ratio. Our data provide the first evidence of sex lability and environment sex determination (ESD) in A. palmeri, suggesting manipulation of sex expression and phenological asynchrony as novel tools for ecological management of dioecious weeds.

plant biology↗