Response of Photosynthetic Pigments and Yield of Pinto Bean (Phaseolus vulgaris L.) to Weed Management Methods

IntroductionBean is one of the most important legumes worldwide for direct human consumption and it is a rich source of protein and carbohydrates. Bean is weak in competing with weeds due to its slow growth during the early stages. Therefore, competition with weeds causes a significant reduction in grain yield at the end of the growing season. Weeds and crops are always competing for obtaining nutrients, water, light and space. Weed competition is a kind of nonliving stress, which effect on plant yield. The photosynthetic capacity of plants depends on abiotic factors such as the quality and quantity of light. Each of the photosynthetic pigments such as chlorophyll a, b and carotenoids absorb light at a different wave length. The rate of photosynthesis and biomass production in plants is also largely dependent on the chlorophyll content of leaves. The weed interference in the plant growth maybe caused a change in the content of carotenoids and chlorophyll pigments in plant leaves. Pinto bean (Phaseolus vulgaris L.) cultivars, with different morphological and genetic characteristics, show different responses in the presence of weeds, which may ultimately result in possible difference in yield. Measurement of growth indices is necessary to study the competitive ability of species during the growth period. Materials and MethodsIn order to investigate the effect of different chemical and non-chemical weed control managements on the yield of determinate and indeterminate bean varieties, an experiment was conducted as factorial based on a randomized complete block design with three replications. This field experiment was carried out in Behshahr, Mazandaran, in 2021. The first factor was different weed control methods: application of trifluralin herbicide as pre-sowing 2.5 liters per hectare; application of trifluralin herbicide 2.5 liters per hectare + one weeding; wheat mulch in the amount of two tons per hectare; application of bentazon 50% of the recommended dose; application of bentazon 75% of the recommended dose; application of bentazon 100% of the recommended dose; weed-free control and control with weed infestation and the second factor includes bean cultivars: Negin variety (determinate growth type) and Sadri variety (indeterminate growth type). Weeds were sampled at flowering and final harvesting stages, and weed species, density, and dry weight of weeds were measured. Also, photosynthetic pigments and yield were investigated.  Results and DiscussionThe results showed that weed species in the field were from 9 plant families and included 10 species. From the total species observed in the field, 4 species have C4 photosynthetic pathway, 4 species have C3 photosynthetic pathway and one species has CAM photosynthetic pathway. The Amaranthus retroflexus L. and Portulaca oleracea L. species had the highest frequency and Chrozophora tinctoria and Physalis alkekengi had the lowest frequency in the field. In all three stages (21 days after planting, flowering and final harvesting stages), the highest density and dry weight of weeds were observed in the control treatment without weeding, and among the weed management treatments, mulch and bentazon 100% treatments caused a decrement in the density and dry weight of weeds in both Negin and Sadri cultivars. Based on the results, the highest chlorophyll a, b and total chlorophyll were observed in both Negin and Sadri cultivars in the weed-free control treatment, and the lowest values were in the control treatment without weeding. Also, the control treatment without weeding had the highest amount of carotenoids in Negin cultivar (0.41 mg.g-1 fresh weight) and in Sadri cultivar (0.37 mg.g-1 fresh weight), while the lowest ones in Negin and Sadri cultivar (0.29 and 0.28 mg.g-1 fresh weight, respectively) was observed in the weed-free control treatment. The highest seed yield of Negin and Sadri cultivar (1957.11 and 2426.01 kg.ha-1, respectively) were observed in the weed-free control treatment. ConclusionsIn general, it can be concluded that the Sadri cultivar with higher competitive ability has performed better against the weed than the Negin cultivar. Among the weed management treatments, the non-chemical management of mulch and the chemical treatment of bentazon 100% had better performance

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

Seed germination requirements of Amaranthus retroflexus L. populations exposed to environmental factors

Seed germination studies are often used to predict the potential of plants to extend their global distribution. In this research, the effect of gibberellic acid (GA3 ) concentrations, pre-chilling, temperature, water and salt stresses, pH, high-temperature pretreatment, planting depth, and flooding on seed germination and seedling emergence of three Amaranthus retroflexus L. populations was investigated. GA3 concentration significantly affected seed germination of all three A. retroflexus populations grown under light/dark conditions. All three populations germinated under constant (10, 15, 20, 25, and 30◦C) and alternating (20/15, 25/18, and 35/25◦C (day/night)) temperatures. The optimum alternating temperature for germination of all three populations was 18/25◦C day/night. Seed germination was severely reduced under moisture and salt stresses. Seedling emergence was reduced on the soil surface by increasing the planting depth from 2.5 to 7.5 cm, and no seedlings emerged when the planting depth of seeds was more than 10 cm. The results of this research help us to understand the germination capacity and requirements of A. retroflexus in different environments and also provide information to help better control the weed

Seed germination requirements of <i>Amaranthus retroflexus</i> L. populations exposed to environmental factors

Seed germination studies are often used to predict the potential of plants to extend their global distribution. In this research, the effect of gibberellic acid (GA3) concentrations, pre-chilling, temperature, water and salt stresses, pH, high-temperature pretreatment, planting depth, and flooding on seed germination and seedling emergence of three Amaranthus retroflexus L. populations was investigated. GA3 concentration significantly affected seed germination of all three A. retroflexus populations grown under light/dark conditions. All three populations germinated under constant (10, 15, 20, 25, and 30 °C) and alternating (20/15, 25/18, and 35/25 °C (day/night)) temperatures. The optimum alternating temperature for germination of all three populations was 18/25 °C day/night. Seed germination was severely reduced under moisture and salt stresses. Seedling emergence was reduced on the soil surface by increasing the planting depth from 2.5 to 7.5 cm, and no seedlings emerged when the planting depth of seeds was more than 10 cm . The results of this research help us to understand the germination capacity and requirements of A. retroflexus in different environments and also provide information to help better control the weed. </jats:p

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.</jats:p