ARTICLE | doi:10.20944/preprints202101.0165.v1
Subject: Biology, Anatomy & Morphology Keywords: base temperature; base water potential; predictive weed emergence model; weed germination
Online: 8 January 2021 (14:12:28 CET)
The efficacy of weed management depends on the correct control timing according to the seedling emergence dynamics. Since soil temperature and soil moisture are two main factors that determine weed germination, the hydrothermal time model can be used to predict their emergence. The aim of this study was to estimate the base temperature (Tb) and base water potential (Ψb) for germination of Chenopodium album, Amaranthus retroflexus, Setaria pumila and Panicum capillare collected from fields in continental Croatia and then to compare these values with those of Italian populations embedded in the AlertInf model. Germination tests were performed at seven constant temperatures (ranging from 4 to 27°C) and eight water potentials (0.00 to - 1.00 MPa). Estimated Tb and Ψb were 3.4°C, -1.38 MPa for C. album, 13.9°C, -0.36 MPa for A. retroflexus, 6.6°C, -0.71 MPa for S. pumila and 11.0°C, -0.87 MPa for P. capillare, respectively. According to the criterion of overlap of the 95% confidence intervals, only Tb of C. album, and Ψb of A. retroflexus were similar between Croatian and Italian populations. Further field experiments should be conducted in the Croatian field to monitor weed emergence patterns of C. album and to calibrate the AlerInf equation parameters.
ARTICLE | doi:10.20944/preprints202112.0157.v1
Subject: Life Sciences, Other Keywords: crop-improvement; population genetics; weed suppression; sustainable weed management; Palmer amaranth; glyphosate
Online: 9 December 2021 (14:50:33 CET)
Increasing agricultural productivity is indispensable to meet future food demand. Crop im-provement programs rely heavily on genetic diversity. The success of weeds in the ecosystem can be attributed to genetic diversity and plasticity. Weedy rice, a major weed of rice, has diverse morphology and phenology, implying wide genetic diversity. Study was conducted to genotype weedy rice accessions (n =54) previously phenotyped for herbicide tolerance and allelopathic potential using 30 SSR markers. Cultivated rice (CL163, REX) and allelopathic rice (RONDO, PI312777, PI338047) were also included in the study. Nei’s genetic diversity among weedy rice (0.45) was found to be higher than cultivated rice (0.24) but less than allelopathic rice (0.56). The genetic relationship and population structure based on herbicide tolerance and allelopathic po-tential were evaluated. Herbicide-tolerant and susceptible accessions formed distinct clusters in the dendrogram, indicating their genetic variation, whereas no distinction was observed between allelopathic and non-allelopathic weedy rice accessions. Weedy rice accession B2, which was previously reported to have high allelopathy and herbicide tolerance, was genetically distinct from other weedy rice. Results from the study will help leverage weedy rice for rice improvement programs as both rice and weedy rice are closely related, thus having a low breeding barrier.
ARTICLE | doi:10.20944/preprints202109.0057.v1
Subject: Life Sciences, Other Keywords: tomato cultivar; allelopathy; competitive ability; plant-plant interactions; weed suppression; sustainable agriculture; weed management; vegetable
Online: 3 September 2021 (10:33:20 CEST)
The present study aims to identify tomato (Solanum lycopersicum L.) cultivars with weed-suppressive ability against target weed species in the tomato growing season. A greenhouse study was conducted with 17 tomato cultivars and target weeds Palmer amaranth (Amaranthus palmeri S. Wats), yellow nutsedge (Cyperus esculentus L.), and large crabgrass (Digitaria sanguinalis L.). Tomato plants and weed species were grown in the same pot. The height, chlorophyll, and dry weight biomass of the weeds were measured 28 days after sowing. The largest effect of tomato interference was on Palmer amaranth. Cultivar 15 reduced Palmer amaranth height, chlorophyll, and biomass by 58, 28, and 83%, respectively. Chlorophyll percentage of yellow nutsedge seedlings was suppressed by 15% by cultivar 64, whereas 13% of its height was reduced by cultivar 20. Cultivar 15 reduced biomass of yellow nutsedge by 40%. The percentage of chlorophyll of large crabgrass was reduced by 22% with cultivar 5, whereas the height and biomass were reduced by 35 and 44% with cultivars 38 and 63, respectively. Factoring all parameters evaluated, cultivars 38, 33, and 7 were most suppressive against the problematic weed species in tomato.
ARTICLE | doi:10.20944/preprints202207.0289.v1
Subject: Biology, Agricultural Sciences & Agronomy Keywords: Planting method; Seedlings; Value index; Weed, Tillering; Efficiency
Online: 19 July 2022 (14:17:25 CEST)
A field experiment was conducted at farmer field of Sundarbazar, Lamjung during rainy season of 2020 with an objective to determine the dynamics of weed with respect different planting methods and varieties. The experiment was laid out in split plot design with three replications where five Varieties (KabreKodo 1, KabreKodo 2, Dalle 1, Okhale 1 and local) were used as the main plot factor and three planting methods (Direct sowing;10*10cm, Conventional transplanting;10*10 cm with 15 days old seedlings and System of Crop Intensification;25*25 cm with 30 days old seedlings) as sub plot factor. Result showed that among 5 genotypes of weeds based on Importance value index, Cyperusrotundus was the most dominant during the initial stage but after the first weeding, Aegeratumhaustinianum dominated the field. Weed biomass and density was recorded highest in directly sown field than that in transplanted field. Among the transplanted crop, weed infestation was seen higher in SCI than in conventionally transplanted finger millet due to wider spacing. But after the first hand weeding, due to profuse root growth and tillering in SCI, weeds were suppressed and thus weed biomass was observed higher in CT. After one hand weeding, SCI showed higher weed control index, crop resistance index and planting method efficiency index in terms of yield. Weed infestation was observed higher in Dalle 1 among varieties.
ARTICLE | doi:10.20944/preprints202109.0451.v1
Subject: Biology, Agricultural Sciences & Agronomy Keywords: Allelopathy; Gossypium hirsutum; chromosome substitution; sustainable weed management.
Online: 27 September 2021 (12:56:50 CEST)
Palmer amaranth (Amaranthus palmeri) is a problematic common weed species, especially in cotton (Gossypium hirsutum). With the wide use of chemical herbicide and herbicide-tolerant transgenic cotton lines, Palmer amaranth populations have developed tolerance to commonly used herbicides. It is imperative to develop alternative weed control methods to slow the evolution of herbicide-resistant weed populations and provide new sources for weed management. Eleven chromosome substitution (CS) cotton lines CS-B26lo, CS-T17, CS-B16-15, CS-B17-11, CS-B12, CS-T05sh, CS-T26lo, CS-T11sh, CS-M11sh, CS-B22sh, and CS-B22lo were screened for weed-suppressing abilities in this study. The cotton lines were tested using the established stair-step structure methodology, which provided scope to study the effect of individual CS lines on the growth and development of Palmer amaranth weed without any interference of other external factors in the greenhouse. Height (cm) and chlorophyll concentration (cci) were measured for each plant in the system. The data were analyzed as a randomized complete block design using LSD mean comparisons of the genotypes at the P≤ .05 level. The 14th day after establishment resulted in the most significant variation in Palmer amaranth height reduction among the CS lines. Results indicated that CS-B22sh had the highest effect in reducing Palmer amaranth height and chlorophyll concentration with the most heightened susceptibility for Palmer amaranth. The cluster analysis revealed that Enlist® cotton, CS-CS-B22sh, and CS-T26lo were clustered in one group suggesting similar genetic potential with reference to Palmer amaranth growth and development. CS-B22sh showed novel genetic potential to control the growth and development of Palmer amaranth, a major weed in cotton fields. In the future, it will be interesting to investigate if CS-B22sh exudates from its root contain allelochemicals able to impede the growth and development of Palmer amaranth.
ARTICLE | doi:10.20944/preprints201807.0177.v1
Subject: Biology, Forestry Keywords: weed control; competing vegetation; yield modelling; E. globulus
Online: 10 July 2018 (12:04:37 CEST)
Several studies have quantified the responses of Eucalyptus globulus plantations to weed control on its early development (2-3 years after establishment). However, long-term results of competing vegetation effects have been rarely incorporated into growth and yield models that forecast the long-term effects of reducing the intensity of competing vegetation control and its interaction with site resource availability on stem volume production close to rotation age. We compared several models predicting stand stem volume yield of Eucalyptus globulus plantations established across a water and fertility gradient growing under different intensity levels of free area of competing vegetation maintained during the first 3 years of stand development. Four sites were selected encompassing a gradient in rainfall and amount of competing vegetation. Treatments were applied at stand establishment and were monitored periodically until age 9 years. Competing vegetation control intensity levels considered 0, 5, 20, 44 and 100% weed-free cover around individual E. globulus seedlings. Maximum competing vegetation biomass production during the first growing season were 2.9, 6.5, 2.2 and 12.9 Mg ha-1, for sites ranging from low to high annual rainfall. As expected, reductions in volume yield at age 9 years were observed as competing vegetation control intensity decreased during the first growing season. A strong relationship was established between stem volume yield loss and the intensity of competing vegetation control, the amount of competing vegetation biomass produced during the first growing season and mean annual rainfall. The slope of the relationship was different among sites and was related mainly to water and light limitations. Our results, suggest that the biomass of competing vegetation (intensity of competition) affecting site resource availability, contribute to observed long-term effects on E. globulus plantations productivity. The site with the lowest mean annual rainfall showed the highest volume yield loss at age 9 years. Sites with highest rainfall showed contrasting results related to the amount of competing vegetation biomass.
ARTICLE | doi:10.20944/preprints202103.0047.v3
Subject: Biology, Anatomy & Morphology Keywords: Sustainable agriculture; allelopathy; biocidal potential; phytotoxic effects; weed management.
Online: 22 March 2021 (12:00:35 CET)
Along with climate change, the native forest replacement by exotic species, such as Eucalyptus globulus, is contributing to a highly fire-prone environment. Since E. globulus detains several post-fire regeneration strategies, sustainable practices are needed to manage eucalyptus stands. Thus, eucalyptus allelopathic potential can be used for weed control. Therefore, this study aimed at assessing the herbicidal potential of post-fire regenerated E. globulus leaves in Portulaca oleracea, and unraveling the main physiological processes disturbed by biocide application. For this, an aqueous extract prepared with fresh leaves (FLE; 617 gfresh weightL-1) and other with oven-dried leaves (DLE; 250 gdry weightL-1) were prepared and foliar-sprayed twice-a-week at different dilutions in 7-days-old purslane plants. As positive control, glyphosate was used. After five weeks, results revealed that DLE at the highest dose detained the greatest herbicidal activity against P. oleracea. To understand how DLE impacted weed physiology, several biochemical and redox-related parameters were evaluated in purslane plants treated with DLE highest dose. Results suggested an overproduction of hydrogen peroxide, causing severe oxidative damage in roots. Overall, this study showed that young E. globulus dried leaves had powerful herbicidal properties against P. oleracea and can represent a feasible approach for weed management, while reducing fire hazard.
ARTICLE | doi:10.20944/preprints201806.0231.v1
Subject: Medicine & Pharmacology, General Medical Research Keywords: green bitter weed; Hymenoxys odorato; liver and kidney toxicity
Online: 14 June 2018 (11:07:44 CEST)
Background: Medicinal plants are of great importance to health of individual and communities. About 80% of the population in Uganda relies on traditional medicine because western-trained medical personnel are limited especially in villages. Most Ugandans use Hymenoxys odorato for medicinal purposes e.g. to treat colds, fever, coughs, anti-helminthes, locally used as tea, anti-allergy and also as an anti-venom to relieve snake bites. Method: A group of 25 male wistar rats of 150 g–210 g were kept for 14 days while being fed and treated with the extract. At 14th day, anesthesia was given and blood samples collected by cardiac puncture for hematological and biochemical investigations. Serum was analyzed for Alkaline Phosphatase, Aspartate Transaminase and Alanine Transaminase while whole blood was used for complete blood count. The liver and kidney were removed and placed in 10% formalin to prepare for histology staining using haematoxylin and eosin technique. Results: The extract elevated hepatic biomarker enzymes i.e. ALP, ALT and AST. The increase was found to be significantly different (P > 0.05) at 400 and 500 mg/kg doses as compared to the control group. Histological sections of the liver showed distortion of liver cytoarchitecture, steatosis, necrosis of hepatocytes and congestion of the sinusoids at high doses 300, 400 and 500 mg/kg body weight. In the sections of the kidney, there was mild distortion of the integrity of the kidney with glomerular hypercellularity at high doses (400 and 500 mg/kg per body weight). Conclusion: Hymenoxys odorato aqueous extract has toxic effects on the liver and kidney of wistar rats. The effects were observed to be in a dose dependent manner.
ARTICLE | doi:10.20944/preprints202108.0288.v1
Subject: Life Sciences, Biotechnology Keywords: stem implanted capsule; bioherbicide; parkinsonia; woody weed; dieback; mechanical delivery
Online: 13 August 2021 (08:34:59 CEST)
An infestation of parkinsonia (Parkinsonia aculeata) located on Alexandria Station, Northern Territory, Australia was successfully treated with a bioherbicide using stem implanted capsules. The bioherbicide containing three endemic endophytic fungi (Lasiodiplodia pseudotheobromae, Macrophomina phaseolina and Neoscytalidium novaehollan-diae) is the first Australian registered woody weed bioherbicide. The product was effectively administered to the plant stems using a mechanical device, resulting in subsequent development of a dieback event, which, after a period of establishment, has moved through the adjacent untreated plant population resulting in significant decline in infestation vigour and reduced recruitment. This is the first report of large-scale management of parkinsonia by this method.
ARTICLE | doi:10.20944/preprints202101.0535.v1
Subject: Keywords: annual weeds; conservation agriculture; perennial weeds; reduced tillage; weed seedbank
Online: 26 January 2021 (11:35:27 CET)
When farmers first shift from conventional tillage (CT) to conservation agriculture (CA) practice the control of weeds may be more difficult due to the absence of tillage. However, in the longer term (3-5 years), CA changes to weed dynamics may alter the weed seedbank. The nature of weed seedbank changes over time in intensively cropped rice-based rotations, that are typical of the Eastern Gangetic Plain, are not well understood. Three long term CA experiments were sampled (at Rajbari after 3 years and Rajshahi after 5 years) for effects of decreased soil disturbance strip planting (SP) and bed planting (BP) at both sites and Zero tillage (ZT) at Rajbari, increased retention of standing residues of previous crops (20 vs 50 %). The weed seedbank in 0-15 cm soil was quantified by assessing emergence from trays a net-house experiment during January-December 2016. The year-round count of emerged weeds revealed the fewest number of weed species (especially broadleaf weeds) and lowest weed density in SP followed by CT, BP, and ZT with 50% crop residues. The SP, BP, and ZT produced a higher number of perennials weeds than annual weeds, which was the opposite of CT. The continuous practice of SP and increased crop residue retention for 3 or more years decreased the size of weed seedbank but increased the relative proliferation of perennial weeds compared to CT. Weed seedbank size in SP was even smaller than BP and ZT.
ARTICLE | doi:10.20944/preprints202004.0309.v1
Subject: Biology, Plant Sciences Keywords: growth rate; vigor; UAV; sUAS; organic; weed competitiveness; Phaseolus vulgaris
Online: 19 April 2020 (01:30:11 CEST)
Vigorous early-season growth rate allows crops to compete more effectively against weeds and to conserve soil moisture in arid areas. Many crop species, including common bean, show genetic variation in growth rate between varieties. Despite this, the genetic basis of the early-season growth-related traits has not been well resolved in the species, in part due to historic phenotyping challenges. Using a range of UAV- and ground-based methods, we evaluated early-season growth vigor of two populations. These growth data were then used to find QTLs associated with several growth parameters. Our results suggest that early-season growth rate is the result of complex interactions between several genetic and environmental factors and highlight the need for the high-precision phenotyping provided by UAVs. The QTLs identified in this study are the first in common bean to be identified remotely using UAV technology and will be useful for developing crop varieties that compete with weeds more effectively. Ultimately, this will reduce crop losses and mitigate the need for herbicides and manual labor for weed control.
ARTICLE | doi:10.20944/preprints201808.0486.v1
Subject: Biology, Agricultural Sciences & Agronomy Keywords: mesocosm; irrigation canal; irrigation channel; degradation; biodegradation; persistence; aquatic weed
Online: 29 August 2018 (08:58:03 CEST)
Endothall dipotassium salt and monoamine salt are herbicide formulations used for controlling submerged aquatic macrophytes and algae in aquatic ecosystems. Microbial activity is the primary degradation pathway for endothall. To better understand what influences endothall degradation, we conducted a mesocosm experiment to 1) evaluate the effects of different water and sediment sources on degradation, and 2) determine if degradation was faster in the presence of a microbial community previously exposed to endothall. Endothall residues were determined with LC-MS at intervals to 21 days after endothall application. Two endothall isomers were detected. Isomer-1 was abundant in both endothall formulations, while isomer-2 was only abundant in the monoamine endothall formulation and was more persistent. Degradation did not occur in the absence of sediment. In the presence of sediment degradation if isomer-1 began after a lag phase of 5-11 days and was almost complete by 14 days. Onset of degradation occurred 2-4 days sooner when the microbial population was previously exposed to endothall. We provide direct evidence that the presence and characteristics of sediment are of key importance in the degradation of endothall in an aquatic environment, and that monoamine endothall has two separate isomers that have different degradation characteristics.
ARTICLE | doi:10.20944/preprints201807.0056.v1
Subject: Biology, Agricultural Sciences & Agronomy Keywords: parthenium weed, soil seedbank, soil depth, seed extraction, sieve shaker
Online: 3 July 2018 (16:02:13 CEST)
Weed seedbank is an indication of future weed infestation potential of the species and is essential for making strategic planning for its sustainable management. Parthenium weed (Parthenium hysterophorus L.) is an invasive alien species threatening the biodiversity and the environment in Malaysia. A study was, therefore, conducted to estimate the soil seedbank of the weed at four soil depths of four villages of Kuala Muda, Kedah. The aim was to indicate the critical s of parthenium weed seedbank in Malaysia. Soil samples were collected from the sites using a soil core. The seeds were extracted from the soil samples with sieve shaker at the Universiti Malaysia Kelantan laboratory, Jeli Campus. The study indicates that the weed seedbank is in critical level at the area. The highest number of weed seeds (6915/m2) was found in Kg. Kongsi 6, followed by Kg. Sungai Tok Rawang (4481 seeds/m2). The top layer of soil, 0-5 cm, contained the maximum number of weed seeds (4878 seeds/m2) and a significant number of seeds (316 seeds/m2) were noticed at 10-15 cm soil depth. The study suggests the Malaysian government to take immediate action to control parthenium weed seedbank of the sites.
ARTICLE | doi:10.20944/preprints202209.0159.v1
Subject: Biology, Ecology Keywords: dormancy continuum; conditional dormancy; physiological dormancy; synchrony pattern; weed population dynamics
Online: 13 September 2022 (05:37:49 CEST)
In every agricultural setting, weed seeds can be found in every cubic centimeter of soil. Weed seeds, as a valuable trait underlying the fate of weed populations, exhibit differing levels of seed dormancy, ensuring their survival under uncertain conditions. Seed dormancy is considered as an innate mechanism that constrains germination under suitable conditions that would otherwise stimulate germination of non-dormant seeds. This work provides new insight into changes in germination patterns along the dormant to nondormancy continuum in seeds with physiological dormancy. Notable findings are: (1) germination synchrony can act as a new parameter that quantitatively describes dormancy patterns and subsequently weed population dynamics, (2) germination synchrony is dynamic, suggesting that the more dormancy decreases, the more synchrony is obtainable, (3) after-ripening and stratification can function as a synchronizing agent that regulates germination behavior. Brassica napus showed the most synchronous germination with the value of 3.14, while lower level of germination asynchrony was for Sinapis arvensis, with the asynchrony value of 2.25. After-ripening and stratification can act as a synchronizing factor through decreasing asynchrony level and increasing synchrony. Weed establish a firm relationship between dormancy cycling and germination synchrony patterns, ensuring their survival and reproductive strategies. By germinating in synchrony, which is accompanied by cycling mechanisms, weeds have more opportunities to persist. The synchrony model used in the present study predicts germination behavior and synchrony along the dormant to nondormancy continuum in weed seeds with physiological dormancy, suggesting a useful method for quantification of germination strategies and weed population dynamics.
ARTICLE | doi:10.20944/preprints202111.0076.v1
Subject: Biology, Agricultural Sciences & Agronomy Keywords: Weed science; Plant-microbe interactions; Medicinal plants; shotgun metagenomics; soil metabarcoding
Online: 3 November 2021 (09:19:12 CET)
The purpose of this paper is to elucidate the roles that microbes may be playing in the rootzone of the medicinal plant Datura inoxia. We hypothesized that rhizospheric and endophytic microbes would be found that were capable of performing the same secondary metabolic functions of the plant rootzone they inhabited. We also hypothesized that the microbial functions would be co-operative with and supportive to plant secondary metabolite production, for example, by providing precursors to important plant bioactive molecules. The methods employed were mi-crobial barcoding, tests of essential oils against antibiotic resistant bacteria and other soil bacterial isolates, 16S Next Generation Sequencing (NGS) metabarcoding, and Whole Genome Shotgun (WGS) taxonomic and functional. A few of the main bacterial genera of interest that were dis-covered in the Datura root microbiome were Flavobacterium, Chitinophaga, Pseudomonas, Strepto-myces, Rhizobium, and Bacillus. In the context of known interactions, and current results, plants and microbes influence the flavonoid biosynthetic pathways of one other, in terms of the regulation of the phenylpropanoid pathway. This is important because these compounds are phyto-protective antioxidants and are precursors to many aromatic bioactive compounds that are relevant to human health. There was strong evidence to support the notion that synergistic production of plant de-rived secondary metabolites by microbes occurred, as well as the ability for the compounds to enter plant cells. There are possible biopharmaceutical and agricultural applications of the natural interplay that was discovered during this study of the Datura inoxia rhizosphere.
ARTICLE | doi:10.20944/preprints202010.0184.v1
Subject: Biology, Anatomy & Morphology Keywords: far-red light; kin recognition; light quality; shade avoidance; weed competition
Online: 8 October 2020 (21:17:04 CEST)
Studies on crop response to light quality [red (R) to far-red (FR) light ratio] often recommend early weed removal to reduce the effects of shade avoidance responses on crop yield. However, it is unclear whether crops are able to distinguish reflected light quality of kin from that of non-kin. We evaluated the response of sugarbeet (Beta vulgaris L.) to reflected FR light from sugarbeet, common lambsquarters (Chenopodium album L.), Kentucky bluegrass (Poa pratensis L.), alfalfa (Medicago sativa L.), and bare soil (control) under outdoor conditions in 2016 and 2017. Treatments were completely randomized with 10 replications per treatment. The study methods ensured there was no direct resource competition. The reflected R:FR of plant species ranged from 0.06 (common lambsquarters) to 0.24 (sugarbeet) compared to 0.7 for the bare soil. In both 2016 and 2017, there were 2 to 4 more leaves in the sugarbeet surrounded by soil compared to sugarbeet surrounded by neighboring species. There was up to 47, 57, 43, and 23% reduction in sugarbeet leaf area, shoot dry weight, root diameter, and root dry weight, respectively, due to reflected R:FR light from neighboring species. Sugarbeet did not respond differently to reflected light quality of kin compared to non-kin.
Subject: Biology, Agricultural Sciences & Agronomy Keywords: weed management; integrated tillage; integrated mowing; herbicide; biodiversity and fruit production
Online: 30 July 2020 (12:19:14 CEST)
Despite the productivity, achieving long-term sustainability and maintaining plant biodiversity become the pivotal goals in orchard floor management, especially along tree rows. Thus, the paradigm of eradicating weeds in the tree row using chemical herbicide or repeated soil tillage needs to be substituted with more sustainable alternatives. This study was conducted in two commercial apple and peach orchards in Marche region (Italy). Two integrated mechanical approaches, integrated mowing (mower + brush or disc) and integrated tillage (blade weeder + integrated mowing), were compared with standard herbicide system in a 2-years trial. Weed species abundance, soil coverage rate, and weed biomass productions, including gas exchange parameters, tree growth, fruit yield and quality were measured. Both integrated practices had significant effects on the number of weed species, total vegetation coverage, and dry weed biomass production. No significant differences were found in terms of tree gas exchange parameters, growth and fruit yield. However, a few fruit quality parameters such as fruit firmness, solid soluble content and dry matter content responded positively to the integrated practices. These results suggest that the integrated mechanical approaches of weed management increased orchard biodiversity, and they had no adverse effects on tree growth, fruit yield, and quality.
ARTICLE | doi:10.20944/preprints202209.0001.v1
Subject: Biology, Agricultural Sciences & Agronomy Keywords: weed management; population dynamics; simulation model; gross margin; environmental impact; decision making.
Online: 1 September 2022 (02:23:49 CEST)
A crop-weed simulation model is presented to compare and evaluate Integrated Weed Management (IWM) strategies. Specifically, the model was parameterized for soybean crops in competition with Euphorbia davidii Subils. We used both, weed and crop demographic data surveyed in agronomic fields of the central zone of the Buenos Aires province, Argentina, throughout two crop cycles (2011/2012 and 2013/2014). The proposed model underwent a calibration process and subsequent validation with 70/30 % data split respectively (N=37). Two annual-based and one multiannual-based case studies were simulated to demonstrate the performance of the model. Different IWM strategies were compared under both, operational and tactical planning horizons through the evaluation of different model outcomes (i.e. crop yield, interspecific competition, economic return, and environmental impact). Our case studies results suggest that the inclusion of cultural management practices could reduce weed interspecific competition by 46 to 97 % and weed seed production by 40 to 89%. An increment in both expected crop yield, by 6 to 20%, and annual gross margin, by 44 to 199 US$.ha-1, were obtained in silico for similar levels of environmental impact.
ARTICLE | doi:10.20944/preprints202208.0079.v1
Subject: Biology, Agricultural Sciences & Agronomy Keywords: pepino mosaic virus (PepMV); Solanum elaeagnifolium; S. rostratum; tomato brown rugose fruit virus (To-BRFV); virus reservoir; weed management
Online: 3 August 2022 (08:35:30 CEST)
Invasive weeds cause significant crop yield and economic losses in agriculture. The highest in-direct impact may be attributed to the role of invasive weeds as virus reservoirs especially within the commercial growing areas. The new tobamovirus tomato brown rugose fruit virus (ToBRFV), recently identified in the Middle-East, overcomes the Tm-22 resistance allele in the cultivated tomato varieties grown in greenhouses. In this study, we determined the role of invasive weed species as potential hosts for ToBRFV and pepino mosaic virus (PepMV). Out of all tested weed species, the invasive species So-lanum elaeagnifolium and S. rostratum, mechanically inoculated with ToBRFV, were positive for To-BRFV in both enzyme linked immunosorbent assay (ELISA) and RT-PCR tests. S. rostratum was also positive for PepMV. No conspicuous phenotype was observed on ToBRFV infected S. elaeagnifolium plants suggesting a hostplant associated defense response. S. rostratum plants inoculated with either ToBRFV alone or a mixture of ToBRFV and PepMV-IL, contained high ToBRFV levels. In addition, when inoculated with ToBRFV or PepMV-IL disease symptom manifestations were observed in S. rostratum plants and the symptoms were exacerbated upon mixed infections with both viruses. The distribution and abundance of both Solanaceae species increase the risks of virus transmission between species.
ARTICLE | doi:10.20944/preprints201808.0493.v1
Subject: Life Sciences, Genetics Keywords: Weed competitive ability; early seed germination and seedling vigor traits; quantitative trait loci (QTLs); single nucleotide polymorphism; direct seeded rice
Online: 29 August 2018 (10:46:02 CEST)
Weed competitive ability (WCA) is a desirable key trait for the improvement of grain yield under direct-seeded rice (DSR) and the aerobic rice ecosystem. The present study targeted screening of 167 introgression lines (ILs) of a Green Super Rice (GSR) IR2-6 population derived from a cross between Weed Tolerant Rice 1 (WTR1) as the recipient parent and Y134 as the donor parent developed at IRRI for weed competitiveness in screen house conditions (SHC). The ILs were phenotyped for WCA traits such as early seed germination (ESG) and early seedling vigor (ESV) in Petri dishes and pot experiment conditions. The results of phenotypic variance revealed ESG-related traits, especially first germination count (1st GC) that positively correlated with second germination count (2nd GC), germination percentage (GP), total dry weight (TDW), total fresh weight (TFW), and vigor index (VI-1), whereas, in ESV, all the traits were positively correlated with each other except for three traits: root dry weight (RDW), 1st GC, and GP-2. The ESG and ESV traits are vital for weed competitiveness. A 6K SNP array was used to study the genetic association for the WCA traits. Forty-four QTLs for WCA traits were mapped on all chromosomes (except on chromosomes 4 and 8) through single marker analysis (SMA). Out of 44 QTLs, 29 were associated with ESG traits and 15 with ESV traits, with LOD scores of 2.93 to 8.03 and 2.93 to 5.04 and explained phenotypic variance ranging from 7.85% to 19.9% and from 7.85% to 13.2%, respectively. However, 31 QTLs were contributed by a negative additive allele from Y134, whereas a positive additive allele was contributed by WTR1 in 13 QTLs. Among them, two QTL hotspot regions were mapped on chromosome 11 (24.7-27.9 Mb) and chromosome 12 (14.8-17.4 Mb). The majority of the QTLs related to WCA traits were grouped into two QTL hotspots: QTL hotspot-I (qAFW11.1, qFC11.1, qFC11.2, qSC11.1, qGP-111.1, qGP-111.2, qTFGS11.1, qVI-111.1, and qVI-111.2) and QTL hotspot-II (qFC12.1, qFC12.2, qSC12.1, qFC12.2, qGP-112.1, qGP-112.2, qTFGS12.1, qTFGS12.2, qVI-112.1, qIV12.2, qFC12.1, and qGC12.2), and a few of them were co-localized on chromosomes 11 and 12. Further, we fine-tuned in the genomic regions of QTL hotspots and identified a total of 13 putative candidate genes on chromosomes 11 and 12 collectively. The present study is the first report on the genetic basis of WCA-related traits and the co-localized QTLs, which could be highly valuable in future breeding programs aiming to improve WCA in rice.