Biology subjects

Mesgaran, M. B.

Publications and source records attributed to Mesgaran, M. B..

3 recordsLinked to original sources

bioRxiv2025

Comparative Analysis of Ecological and Germination Niches in Native and Invasive Populations of Amaranthus albus

Invasive species serve as natural experiments to study adaptive evolution over contemporary time scales, as their native and invasive populations are exposed to different climatic settings and hence may experience strong selection pressures. In the life cycle of plants, germination stands as a cornerstone; thus, when invasive plant species encounter new surroundings, it is primarily expected that their germination niche will adapt to align with the thermal characteristics of the environment. However, adaptive responses in germination traits, specifically in cardinal temperatures, have not been explored. The objective of this study is to compare the Amaranthus albus (tumble pigweed) germination thermal niche and ecological niche between its native and invaded ranges. Considering geographic areas and climatic conditions, populations of A. albus were gathered from both cold and warm habitats in its native range (US) and its invaded range (Israel), with populations being at least 20 km apart from each other. First, populations were grown under similar conditions in a common garden experiment until seed production. The progeny seeds produced were then subjected to a set of germination trials under gradually changing temperature regimes. Cardinal temperatures and thermal niches for each population were estimated and analyzed in relation to the local climatic conditions of their respective habitats. Finally, a germination window was calculated to characterize the germination of a population throughout the year within its habitat. The invaded range studied here represents a subset of the species native range, with the A. albus establishing in similar climatic surroundings. Similarly, the germination niche for the native range was wider than for the invaded range. Thermal differentiation is evident in both native and invaded ranges. Populations from colder habitats exhibit lower base temperatures than those from warmer ones. This association was more evident for native populations. The remarkable variability observed within the germination pattern completely disappeared in the germination window produced by those models, resulting in a similar pattern across the year for all populations. Our findings demonstrate the capability of species to adapt to new environmental conditions that may arise due to climatic changes. It emphasizes the role of cardinal temperatures, specifically the base temperature, as a potential adaptive characteristic.

ecology↗

bioRxiv2025

Pollinate to Suppress: Sterile Pollen and Certation Effects in Palmer amaranth (Amaranthus palmeri)

The sterile pollen technique, which involves applying X-ray irradiated pollen to female plants, has shown promising results in reducing seed production in dioecious Palmer amaranth (Amaranthus palmeri S. Wats.). However, field-scale implementation of this method requires a carrier for pollen delivery, as applying pure pollen on a large scale is not practical. Additionally, variability in flowering time within and among individual plants may impact the techniques effectiveness. Mass pollination may also lead to a female-biased sex ratio in the progeny, a phenomenon known as certation. Therefore, in this study, we aimed to: (1) identify a suitable dry (inert) diluent and the most effective pollen-to-diluent ratio for large-scale application, and (2) determine the most effective combination of initiation time, frequency, and number of sterile pollen applications, and 3) test for evidence of certation in A. palmeri. Plants were grown in the greenhouse in summer 2021. Sterilized pollen irradiated at 300 Gy was mixed with talc or wheat powder flour, respectively, at six v/v ratios (pollen%/powder%) of 0/100 (powder alone), 5/95, 10/90, 25/75, 50/50, or 100/0 (pure irradiated pollen). An equal amount of the pollen-diluent powder mixture was then brushed onto the standardized lengths of inflorescence of receptive female plants. Flower and seed number on each inflorescence was counted and used to calculate seed set in each treatment. The findings showed that a minimum of 25% irradiated pollen in the mixture, either with talc powder or wheat flour, can effectively reduce seed set in A. palmeri. Building on this, a second round of greenhouse experiments was conducted in fall 2021, where female plants were pollinated with a 25% irradiated pollen and talc powder mixture using a powder duster. Pollination treatments were initiated at different times after anthesis (7, 14, and 21 days), and the number of applications varied (once, twice, or three times) with intervals of one, two, or three weeks between applications. The greatest reduction in seed output was achieved when sterile pollen application began seven days after anthesis and was repeated three times at 7-day intervals. Evidence of certation was also observed in A. palmeri, with the progeny of mass-pollinated females showing a higher female ratio (58%) compared to the open-pollinated population (47%). Mass pollination also led to a slight, though not statistically significant, reduction in plant size traits such as height and number of branches, providing an additional potential benefit of the sterile pollen technique.

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↗