Genomic regions associated with herbicide tolerance in a worldwide faba bean (Vicia faba L.) collection

Weeds represent one of the major constraints for faba bean crop. The identification of molecular markers associated with key genes imparting tolerance to herbicides can facilitate and fasten the efficient and effective development of herbicide tolerant cultivars. We phenotyped 140 faba bean genotypes in three open field experiments at two locations in Lebanon and Morocco against three herbicide treatments (T1 metribuzin 250 g ai/ha; T2 imazethapyr 75 g ai/ha; T3 untreated) and one in greenhouse where T1 and T3 were applied. The same set was genotyped using genotyping by sequencing (GBS) which yield 10,794 high quality single nucleotide polymorphisms (SNPs). ADMIXTURE software was used to infer the population structure which revealed two ancestral subpopulations. To identify SNPs associated with phenological and yield related traits under herbicide treatments, Single-trait (ST) and Multi-trait (MT) Genome Wide Association Studies (GWAS) were fitted using GEMMA software, showing 10 and 14 highly significant associations, respectively. Genomic sequences containing herbicide tolerance associated SNPs were aligned against the NCBI database using BLASTX tool using default parameters to annotate candidate genes underlying the causal variants. SNPs from acidic endochitinase, LRR receptor-like serine/threonine-protein kinase RCH1, probable serine/threonine-protein kinase NAK, malate dehydrogenase, photosystem I core protein PsaA and MYB-related protein P-like were significantly associated with herbicide tolerance traits.

Prescriptions For The Control Of A Clonal Invasive Species Using Demographic Models

Until recently, little focus has been given to determine the population dynamics of invasive species and evaluate their genetic variation. Consequently, not much is known of what drives clonal invasive species and their demography. Here we describe the population dynamics of Kalanchoe delagoensis (Crassulaceae), considered invasive to several countries. We quantified the demography of a population in central Mexico using integral projection models (IPM) in a population that reproduced asexually exclusively through plantlets. The effect of clonal recruitment on λ was evaluated by changing plantlet survival and simulating management scenarios that used previous data of watering and seven experimental herbicide treatments. The finite rate of population increase indicated that this Kalanchoe delagoensis population is growing (above one) with significant potential increases that correlated with water availability. The IPM showed that plantlet survival and recruitment were the most critical steps in the cycle for the population and simulations of different management scenarios showed that reducing plantlet survival significantly decreased λ only in two out of the seven herbicides used.

Strategic level of agrocenoses state management

The aim of the work is to develop a theoretical basis for solving the problem of managing the state of agrocenoses, which contain crops of the main crop and weeds. The solution to this problem is aimed at eliminating the limitations of the existing paradigm of separate management of the state of crops and weeds. The proposed theory and methodology is based on taking into account the relationship between the state of crops and weeds, and their overall effect on the content of nutrients in the soil. For this, a system of mathematical models has been proposed, in which these relationships and yield losses are taken into account when the parameters of the chemical state of the soil deviate from the optimal values for crop rotation and from the effect of herbicide treatments on crop sowing. The result of solving the problem is the optimal strategies for the introduction of mineral fertilizers, ameliorants and herbicides by years of crop rotation. These strategies ensure that yield losses are minimized for all crops, rotation and agrochemical consumption. The results obtained are new, since such tools are currently lacking.

Effect of integrated weed management on turmeric under mid hill conditions of Himachal Pradesh

A field experiment was carried out on silty clay loam soil, acidic in reaction, high in available phosphorus, medium in available potassium and low in available N during kharif 2017 at the Research Farm of Department of Agronomy, CSKHPKV, Palampur to study effective weed control strategy for this important crop. The results revealed that Alternanthera philoxeroides was the major weed constituting 16% of the total weed flora. This was followed by Cynodon dactylon and Echinochloa colona with 14 and 12% of total weed population, respectively. The count of Echinochloa colona, Alternanthera philoxeroides, Commelina benghalensis, Digitaria sanguinalis and Ageratum conyzoides was maximum at 120 DAP and there after it gradually decreased. All herbicide treatments brought significant reduction in the count on Echinochloa, Alternanthera and Ageratum over weedy check. The lowest count of these weeds was recorded in metribuzin fb straw mulch fb hand weeding and the maximum count was in case of weedy check. All the weed control treatments significantly reduced the total weed count and dry weight of weeds as compared to the weedy check. Amongst different herbicide treatments application of metribuzin @ 0.70 kg/ha fb straw mulch fb hand weeding resulted in significantly lowest weed count at all stages of observation as well as at harvest though this treatment was at par with metribuzin @ 0.70 kg/ha fb two hand weedings and treatments in which atrazine 0.75 kg/ha and hand weedings were applied with or without the use of straw mulch resulted in significantly lower dry matter accumulation by weeds as compared to other herbicide treatments. Weed index calculated at 120 DAP was highest with use of metribuzin @ 0.70 kg/ha and atrazine @ 0.75 kg/ha used along with straw mulch and one or two hand weedings proving effective as compared to other herbicides tested. From the present study it seems that mulching must be included in any effective weed management strategy for turmeric. Also among different herbicides metribuzin and atrazine are effective and their integration with mulching and/or hand weeding gave good control of weeds in turmeric.

Bioefficacy, Phytotoxicity and Economics of Post-emergence Herbicides in Moth Bean (Vigna aconitifolia) in Hot Arid Regions

Background: Weed infestation is the major cause of yield loss to Kharif pulses in arid regions. Post-emergence herbicide application is a promising weed management option for pulses in these areas. Therefore, the current study was aimed to find an effective and economic post-emergence herbicide molecule for weed control in moth bean. Methods: A field experiment was conducted during 2017-2019 with different herbicides, hand weeding, weed-free and unweededs in Kharif mung bean in a randomized complete block design with three replications. Result: Among the herbicide treatments, post-emergence application of propaquizafop + imazethapyr @ 125 g a.i. ha-1 being statistically at par with clodinafop-propargyl + sodium acifluorfen @ 312.5 g a.i. ha-1 and hand weeding recorded the highest reduction in total weed dry matter (73.9%), highest weed control efficiency (73.8%) and lowest weed persistence index (1.03) compared to the unweeded. The reduction in seed yield in unweeded compared to weed-free and hand weeding was 50.8% and 42.1%, respectively. As the imazethapyr-containing herbicides caused crop phytotoxicity, significantly higher crop dry weight (513 g m-2), seed yield (5.53 q ha-1), stover yield (18.0 q ha-1), gross returns and net benefits of moth bean were recorded with clodinafop-propargyl + sodium acifluorfen (312.5 g a.i. ha-1) over other herbicide treatments. Clodinafop-propargyl + sodium acifluorfen (@312.5 g a.i. ha-1) registered the minimum value of weed index (20) and highest values of herbicide efficiency index (3.9) and crop resistance index (4.70).

Japanese Hops (Humulus japonicus) Control and Management Strategies in Large River Floodplains

Japanese hops (Humulus japonicus) is an invasive vine that establishes in open areas in riverine habitats and suppresses tree regeneration and native vegetation. This study evaluated the use of herbicides and tree plantings to control and manage Japanese hops on five Mississippi River islands over a four-year period. Herbicide treatments included a preemergent (sulfometuron methyl), a postemergent (glyphosate), and a combination of both. Tree plantings used containerized and bareroot American sycamore (Platanus occidentalis) and eastern cottonwood (Populus deltoides) trees. Japanese hops biomass was significantly lower in all herbicide treatments in 2012 and 2015, but the preemergent treatment was less effective than other treatments in 2012 and 2014. After two years, average survivorship of containerized trees was 20%–42%, whereas bareroot seedlings had near 100% mortality. Results indicate that postemergent treatments are effective for short-term control, but large floods reestablish Japanese hops in treated areas. Reforestation, if combined with herbicide treatments and active management, may be a promising approach in large river floodplains that experience frequent flooding, but low tree survivorship presents challenges to reforestation. Study Implications Japanese hops (Humulus japonicus) is an invasive vine that establishes in open riparian areas and suppresses tree regeneration and other native vegetation. We confirmed that glyphosate provides effective short-term control, but also found that large floods can quickly reestablish Japanese hops in treated areas. Bareroot seedling mortality was extremely high, but initial survival and growth rates of containerized trees were more promising. We conclude that tree plantings combined with active maintenance, including glyphosate application, may be a viable option for long-term control of Japanese hops in upper Mississippi River floodplains.

Selectivity of Herbicides Applied in Preemergence and Diuron in Postemergence for Sesame

The expansion of sesame growth has led to one of the biggest challenges in weed management mainly due to the limited options of selective herbicides for the control of eudicots species. This study aimed to evaluate the selectivity of diuron, s-metolachlor or imazethapyr herbicide treatments in isolation, or in a tank mixture, when applied in preemergence only, or association with diuron herbicide sprayed in postemergence during sesame cultivation. Two experiments were carried out under Brazilian Cerrado conditions. In the first experiment, different doses (g ha-1) of diuron (500 and 750), s-metolachlor (480 and 960) and imazethapyr (40 and 80) were applied in preemergence in isolation or in a tank mixture. In the second experiment, doses (g ha-1) of the herbicides diuron (500 and 750) and s-metolachlor (480 and 720) were applied in preemergence isolated or in tank mixture, associated or not with diuron (500 g ha-1) in postemergence. The results indicated that diuron and s-metolachlor applied in isolation or in combination during preemergence are selective to the sesame crop up to the doses of 750 g ha-1 and 720 g ha-1, respectively, and when applied in association with diuron at a dose of 500 g ha-1 in postemergence are also selective for sesame crop.

Influence of sugarcane straw on weed germination control

This research studied the effectiveness of herbicide treatments in weed control and during different periods of emergence, when applied to varying amounts of straw. The experiment was conducted in a greenhouse with pre-emergent herbicides: amicarbazone, metribuzin, indaziflam, isoxaflutole, amicarbazone + indaziflam, metribuzin + indaziflam, and isoxaflutole + indaziflam, against three species (Sorghum halepense, Rottboellia exaltata, and Mucuna aterrima). The experimental design was completely randomized in a 5x4 factorial scheme, with five amounts of straw (0, 1, 2, 3, and 5 t/ha) and four periods of weed emergence (0, 30, 60, and 90 days after treatments). The residual control of indaziflam was influenced by the amount of straw. Metribuzin presented a low residual control, while isoxaflutole was not affected by the amount of straw. Amicarbazone offered residual control for Mucuna aterrima. The association between indaziflam + isoxaflutole displayed a suitable residual control against Sorghum halepense and Rottboellia exaltata. The association of indaziflam + metribuzin adequately controlled Mucuna aterrima and Sorghum halepense. herbicide physical-chemical characteristics can influence their performance, and the association of products may increase residual and weed spectrum control. Highlights This partial or total removal of remaining sugarcane straw from the soil surface alters weeds dynamics in sugarcane fields. In this situation we have monocot and dicot weeds infesting the sugarcane crops. Among these species, some plants are even more difficult to control, such as Sorghum halepense, Rottboellia exaltata, and Mucuna aterrima Indaziflam herbicide presented a better performance in controlling monocotyledonous plants than eudicot plants. The herbicides amicarbazone and metribuzin presented adequate control of Mucuna aterrima despite having lower residual control. The association of indaziflam + metribuzin, resulted in satisfactory results for Mucuna aterrima, Sorghum halepense, and Rottboellia exaltata.

Manipulation of sunflower population density and herbicide rate for economical and sustainable weed management

Field study tested weed control efficacy, crop yield and economic return using various weed management strategies in sunflower growing with different population density. Treatments included four rates of PRE emergence application of S-metolachlor + fluchloridon and one POST emergence application of flumioxazin + quizalofop-pethyl. PRE-em application (1.4 + 2.4 and 1.2 + 2.0) provided at the higher crop densities (70 000) best weed control. However, PRE- em treatments with lower doses (0.8 + 1.6 and 1.0 + 1.8) and POST- em application did not maintain acceptable control of dominant weeds. Grain yield increased with the crop density, but did not statistically differ between applied herbicide treatments. Finally, the implication of this study demonstrated that sole application of tested herbicide treatments at higher crop sowing density (60 000 and 70 000) was found to be economically the best alternative strategy for reducing weed infestation and achieving a better yield.

Is There a Benefit of Adding Atrazine to HPPD-Inhibiting Herbicides for Control of Multiple-Herbicide-Resistant, Including Group 5-Resistant, Waterhemp in Corn?

The evolution of multiple-herbicide-resistant (MHR) waterhemp (resistant to Groups 2, 5, 9, and 14) in Ontario, Canada is challenging for growers. The complementary activity of the co-application of hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicides with atrazine has been well documented. The objective of this research was to determine if the addition of atrazine to 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicides applied postemergence improves their consistency of MHR waterhemp (including Group 5 resistance) in corn. Five field trials were conducted over a two-year period (2018, 2019) in Ontario, Canada. Five HPPD-inhibiting herbicides [isoxaflutole (105 g ha-1), mesotrione (100 g ha-1), topramezone (12.5 g ha-1), tembotrione (90 g ha-1), and tolpyralate (30 g ha-1)] were applied postemergence with and without atrazine to 10-cm-tall waterhemp. Corn injury (≤ 10%) was observed at specific sites where the application of tembotrione, isoxaflutole and isoxaflutole + atrazine resulted in characteristic white bleaching of corn foliage; however, yield was not affected. Averaged across field sites, the addition of atrazine to isoxaflutole, mesotrione, topramezone, or tembotrione improved MHR waterhemp control 15%, 11%, 7%, and 7%, respectively at 4 weeks after application (WAA). Averaged across herbicide treatments and sites, the addition of atrazine reduced the standard error of MHR waterhemp control by 13% to 100%. This study concludes that the co-application of atrazine with HPPD-inhibitors applied postemergence reduced the risk of herbicide failure and resulted in greater and more consistent control of MHR waterhemp.