Phenological characteristics of the invasive weed Cucumis melo

Phenology is the study of periodic biological events. The time of weed appearance, growth and reproduction are very important for decisions on invasive weed management. Cucumis melo is an annual invasive weed of soybean fields in the north of Iran that reproduces and spreads predominately through seed production. In order to study the phenology of wild melon was conducted an experiment in CRD at Research Farm of Gorgan University of Agricultural Sciences and Natural Resources, Iran, during 2012. Seeds first germinated after 10 days of planting, as soon as optimal soil temperatures were achieved. The weed exhibited monoecious tendencies, with production of male flowers rapidly followed by production of both male and female flowers on the same vine. Cucumis melo exhibited prolific fruit production, until senescence occurred at 75 and 92 days after establishment. First fruit formation was observed between 40 and 49 days after emergence, depending on temperature. To complete growth cycle, of Cucumis melo required about 448 and 733 degree days, respectively for late of May and 8 of June. The weed produced a maximum of 100 fruits/plant, but an average plant typically produced 48 fruits/plant. The seed number and seed weight was on average about 190 seeds/fruit and 0.55 g per 100 seeds, respectively. The results indicated that wild melon could produce a lot of fruits and seeds within a growth period of about 75 and 92 days.Keywords: Growth, monoecious plants, reproduction, wild melonPhänologische Eigenschaften der invasiven Unkrautart Cucumis meloZusammenfassungDie Phänologie befasst sich mit wiederkehrenden biologischen Abläufen. Auflauf, Wachstum und Samenproduktion invasiver Arten sind wichtig für Bekämpfungsentscheidungen. Cucumis melo ist eine einjährige, invasive Unkrautart, die im Norden Irans im Sojabohnenanbau vorkommt und sich vorwiegend durch Samenproduktion vermehrt und ausbreitet. Untersuchungen zur Phänologie dieser Unkrautart wurden 2012 auf der Versuchsstation der Gorgan Universität im Iran durchgeführt. Das Auflaufen erfolgte von Anfang bis Mitte Mai nach Erreichen optimaler Bodentemperaturen. Die Unkrautart zeigte monözische Tendenzen indem sowohl männliche als auch weibliche Blüten an einer Pflanze ausgebildet wurden. Cucumis melo zeigt eine starke Fruchtentwicklung bis zum Beginn der Seneszens nach etwa 75 Tagen nach der Keimung. In Abhängigkeit von der Temperatur wurde die erste Fruchtbildung 40 bis 49 Tage nach der Keimung beobachtet. Wachstumszyklus für Ende Mai und 8. Juni abzuschließen, Cucumis melo der erforderlichen etwa 448 und 733 Grad-Tagen. Die Unkrautart produzierte maximal 100 Früchte pro Pflanze und im Mittel produzierte eine Pflanze 48 Früchte. Die Samenanzahl und das Samengewicht lagen bei 190 Samen pro Frucht und 0,55 g pro 100 Samen. Die Ergebnisse zeigen, dass wilde Melonenarten innerhalb von 75 Tagen eine hohe Anzahl von Früchten und Samen produzieren können.Stichwörter: Monoecious Pflanzen, Reproduktion, Wachstum, wilde Melon

Fitness Cost of Imazamox Resistance in Wild Poinsettia (Euphorbia heterophylla L.)

Wild poinsettia (Euphorbia heterophylla L.) is a difficult-to-control weed in soybean production in Brazil that has developed resistance to herbicides, including acetolactate synthase inhibitors. We investigated the potential fitness cost associated to the Ser-653-Asn mutation that confers imazamox resistance in this weed. Plant height, leaf and stem dry weight, leaf area and seed production per plant as well as the growth indices of specific leaf area, leaf area ratio, relative growth rate and net assimilation in F2 homozygous resistant (R) and susceptible (S) wild poinsettia progenies were pairwise compared. S plants were superior in most of the traits studied. Plant heights for S and R biotypes, recorded at 95 days after planting (DAP), were 137 and 120 cm, respectively. Leaf areas were 742 and 1048 cm2 in the R and S biotypes, respectively. The dry weights of leaves and stems in the S plants were 30 and 35%, respectively, higher than in the R plants. In both biotypes, the leaves had a greater share in dry weight at early development stages, but from 50 DAP, the stem became the main contributor to the dry weight of the shoots. The R biotype produced 110 ± 4 seed plant−1, i.e., 12 ± 3% less seeds per plant than that of the S one (125 ± 7 seed plant−1). The growth indices leaf area ratio and specific leaf area were generally higher in the S biotype or similar between both biotypes; while the relative growth rate and net assimilation rate were punctually superior in the R biotype. These results demonstrate that the Ser-653-Asn mutation imposed a fitness cost in imazamox R wild poinsettia

Herbicide Resistance in Phalaris Species: A Review

Weeds, such as Phalaris spp., can drastically reduce the yield of crops, and the evolution of resistance to herbicides has further exacerbated this issue. Thus far, 23 cases of herbicide resistance in 11 countries have been reported in Phalaris spp., including Phalaris minor Retz., Phalaris paradoxa L., and Phalaris brachystachys L., for photosystem II (PS-II), acetyl-CoA carboxylase (ACCase), and acetolactate synthase (ALS)-inhibiting herbicides. This paper will first review the cases of herbicide resistance reported in P. minor, P. paradoxa, and P. brachystachys. Then, the mechanisms of resistance in Phalaris spp. are discussed in detail. Finally, the fitness cost of herbicide resistance and the literature on the management of herbicide-resistant weeds from these species are reviewed

Physiological Fitness Associated to ACCase Target-Site Resistance Enhances Growth and Reproduction in Phalaris brachystachys

Short-spike canarygrass (Phalaris brachystachys (Link.)) from Iranian wheat fields has developed resistance to acetyl-coenzyme A carboxylase (ACCase) inhibitors due to a target-site mutation (Ile-1781-Thr). Target-site resistance mutations may confer pleiotropic effects in weeds. In this paper, the possible effect of the Ile-1781-Thr mutation on the ecological fitness during life cycles in P. brachystachys plants was investigated. ACCase genes of P. brachystachys populations resistant (R) and susceptible (S) to ACCase inhibitors were sequenced and the vegetative growth and reproductive characteristics of the plants were assessed. In the final growth stage (217 days after planting—DAP), R sub-population plants were 30 cm taller than the S plants. Additionally, the R sub-population produced up to 12 leaves and 2.8 tillers more per plant, and accumulated double the dry weight (2850 g m−2) compared to the S sub-population. The leaf area index (LAI) of the R sub-population was 1.1 times higher than that of the S sub-population. In addition, the net assimilation rate (NAR) and plant growth rate (PGR) between 114 and 182 DAP of the R sub-population were 0.11 and 13 g m−2 d−1 higher than the S sub-population, but the relative growth rate (RGR) was similar between R and S sub-populations. The number of spikes (6 vs. 3.8), the spike length (8.4 vs. 5.5), and number of seeds per plant (1276 vs. 751 seed plant−1) of the R sub-population were higher than the S ones, but the weight (3.25 g) and size (11.6 mm2) of 1000 seeds were similar between populations. The R sub-population of P. brachystachys exhibited higher plant growth and reproductive parameters than the S one, which may increase the frequency of resistance in the population in the absence of adequate weed-control methods

The First Case of Short-Spiked Canarygrass (Phalaris brachystachys) with Cross-Resistance to ACCase-Inhibiting Herbicides in Iran

The weed Phalaris brachystachys Link. severely affects winter cereal production. Acetyle-CoA Carboxylase (ACCase)-inhibiting herbicides are commonly used to control this weed in wheat fields. Thirty-six populations with suspected resistance to ACCase-inhibiting herbicides were collected from wheat fields in the Golestan Province in Iran. A rapid test performed in Petri dishes and whole-plant dose–response experiments were conducted to confirm and investigate the resistance level of P. brachystachys to ACCase-inhibiting herbicides. The seed bioassay results showed that 0.02 mg ai L−1 clodinafop-propargyl (CP) and 1.36 mg ai L−1 of the diclofop-methyl (DM) solution were the optimal amounts for reliably screening resistant and susceptible P. brachystachys populations. In the whole plant bioassay, all populations were found to be resistant to CP, resistance ratios ranging from 2.7 to 11.6, and all of the CP-resistant populations exhibited resistance to DM. Fourteen populations showed low resistance to cycloxydim, and thirteen of these populations were also 2-fold resistant to pinoxaden. The results showed that DM resistance in some P. brachystachys populations is likely due to their enhanced herbicide metabolism, which involves Cytochrome P450 monooxygenases, as demonstrated by the indirect assay. This is the first report confirming the cross-resistance of ACCase-inhibiting herbicides in P. brachystachys in Iran

Ile-1781-Leu and Asp-2078-Gly Mutations in ACCase Gene, Endow Cross-resistance to APP, CHD, and PPZ in Phalaris minor from Mexico

Herbicides that inhibit acetyl coenzyme A carboxylase (ACCase) are commonly used in Mexico to control weedy grasses such as little seed canarygrass (Phalaris minor). These herbicides are classified into three major families (ariloxyphenoxypropionates (APP), cyclohexanodiones (CHD), and, recently, phenylpyrazolines (PPZ)). In this work, the resistance to ACCase (APP, CHD, and PPZ) inhibiting herbicides was studied in a biotype of Phalaris minor (P. minor) from Mexico, by carrying out bioassays at the whole-plant level and investigating the mechanism behind this resistance. Dose-response and ACCase in vitro activity assays showed cross-resistance to all ACCase herbicides used. There was no difference in the absorption, translocation, and metabolism of the 14C-diclofop-methyl between the R and S biotypes. The PCR generated CT domain fragments of ACCase from the R biotype and an S reference were sequenced and compared. The Ile-1781-Leu and Asp-2078-Gly point mutations were identified. These mutations could explain the loss of affinity for ACCase by the ACCase-inhibing herbicides. This is the first report showing that this substitution confers resistance to APP, CHD, and PPZ herbicides in P. minor from Mexico. The mutations have been described previously only in a few cases; however, this is the first study reporting on a pattern of cross-resistance with these mutations in P. minor. The findings could be useful for better management of resistant biotypes carrying similar mutations

Tribenuron-methyl metabolism and the rare Pro197Phe double mutation together with 2,4-D metabolism and reduced absorption can evolve in Papaver rhoeas with multiple and cross herbicide resistance to ALS inhibitors and auxin mimics

Multiple resistance mechanisms to ALS inhibitors and auxin mimics in two Papaver rhoeas populations were investigated in wheat fields from Portugal. Dose-response trials, also with malathion (a cytochrome P450 inhibitor), cross-resistance patterns for ALS inhibitors and auxin mimics, alternative herbicides tests, 2,4-D and tribenuron-methyl absorption, translocation and metabolism experiments, together with ALS activity, gene sequencing and enzyme modelling and ligand docking were carried out. Results revealed two different resistant profiles: one population (R1) multiple resistant to tribenuron-methyl and 2,4-D, the second (R2) only resistant to 2,4-D. In R1, several target-site mutations in Pro197 and enhanced metabolism (cytochrome P450-mediated) were responsible of tribenuron-methyl resistance. For 2,4-D, reduced transport was observed in both populations, while cytochrome P450-mediated metabolism was also present in R1 population. Moreover, this is the first P. rhoeas population with enhanced tribenuron-methyl metabolism. This study reports the first case for P. rhoeas of the amino acid substitution Pro197Phe due to a double nucleotide change. This double mutation could cause reduced enzyme sensitivity to most ALS inhibitors according to protein modelling and ligand docking. In addition, this study reports a P. rhoeas population resistant to 2,4-D, apparently, with reduced transport as the sole resistance mechanism.This work has been supported by the Asociacion de Agroquimicos y Medio Ambiente, Spain. Joel Torra acknowledges support from the Spanish Ministry of Science, Innovation, and Universities (grant Ramon y Cajal RYC2018–023866-I) and by the Spanish State Research Agency, Spain (AEI) and the European Regional Development Fund, EU (ERDF) through the projects AGL2017-83325-C4-2-R and PID2020-113229RB- C42. The field surveys made in Portugal were supported by Foundation for Science and Technology through the project UIDB/05064/2020 (VALORIZA). Jorge Lozano-Juste group is funded by grants RYC2020- 029097-I and PID2021-128826OA-I00 from Ministerio de Ciencia e Innovaci ́on (MCIN, Spain), AEI and the ERDF

Interferência e nível de dano econômico de Brachiaria plantaginea e Ipomoea nil na cultura do feijão comum Interference and economic threshold of Brachiaria plantaginea and Ipomoea nil in the common bean crop

As pesquisas acerca do impacto da interferência das plantas daninhas sobre as culturas normalmente são realizadas com uma única espécie infestante, quando na realidade podem ocorrer diversas. Os objetivos deste trabalho foram avaliar a interferência de Brachiaria plantaginea e Ipomoea nil sobre o rendimento de grãos do feijoeiro (Phaseolus vulgaris) e determinar o nível de dano econômico (NDE) de cada espécie na cultura. Foram realizados dois experimentos a campo com as cultivares de feijão 'IPR Graúna' (Grupo Preto) e 'UTF-06' (Grupo Carioca) em convivência com infestações mistas em diferentes proporções aleatórias das espécies B. plantaginea e I. nil. Modelos de regressão múltiplos foram utilizados para determinar a capacidade de interferência de cada espécie daninha sobre a produtividade da cultura. O impacto de interferência de cada planta de I. nil correspondeu a 2,6 e 0,25 quando comparada a cada planta de B. plantaginea, dependente das proporções relativas na comunidade infestante e das condições de cada experimento. A cultivar 'IPR Graúna' apresentou maior habilidade competitiva do que 'UTF-06'. O NDE foi dependente da proporção relativa de cada espécie daninha na comunidade e foi obtido sob baixas infestações (The researches about the impact of weed interference on crops are usually performed with a single weed species, when in reality there are numerous. The objective of this study was to evaluate the interference of Brachiaria plantaginea and Ipomoea nil on the grain yield of French beans (Phaseolus vulgaris) and to determine the economic weed threshold (EWT) of each species on the crop. Two field experiments were conducted with bean cultivars 'IPR Graúna' (Black group) and 'UTF-06' (Carioca group) in coexistence with random proportions of mixed infestations of B. plantaginea and I. nil. Multiple regression models were used to determine the interference abi1lity of each weed species on crop productivity. The interference ability of each plant of I. nil corresponded to 2.6 and 0.25 of each B. plantaginea, dependent on the relative proportions on the weed community and on the conditions of each experiment. Cultivar 'IPR Graúna' showed higher competitive ability than 'UTF-06'. The EWT was dependent on the relative proportion of each weed species in the community and was reached under low infestation (<16 plants m-2) in all conditions tested and simulated