Allelopathic Effect of Aqueous Extracts of Stinkwort (Dittrichia graveolens L.) on Germination and Growth of Some Weed Species

The experiment was implemented by CRD design with three replications and lasted for 40 days, from 5 October until 15 November 2020. Four extract concentrations of D. graveolens 0, 2, 6, and 10% were used. The concentration of 0% was considered as control. The allelopathic effect has been studied on five weed species; Amaranthus retroflexus L., Portulaca oleracea L., Lolium multiflorum Lam., Sorghum halepense L., and Cuscuta campestris Yunck. The research also aimed to determine the effect of Stinkwort extract on the growth of tomato seedlings. All concentrations affected seed germination for all studied weeds. The concentration of 10% was more influential in growth-related indicators compared to other concentrations. The seeds of L. multiflorum and rhizomes of S. halepense were more tolerant to D. graveolens allelochemicals in germination rate than A. retroflexus, P. oleracea, and C. campestris. All concentrations led to a reduction in the weed heights and the wet and dry weights compared with the controls. The effect of the extract with various concentrations was catalytic for the growth of tomato seedlings, as the average height of tomato seedlings was in direct proportion to the concentration.

Allelopathic Effect of Aqueous Extracts of Stinkwort (Dittrichia graveolens L.) on Germination and Growth of Some Weed Species

The experiment was implemented by CRD design with three replications and lasted for 40 days, from 5 October until 15 November 2020. Four extract concentrations of D. graveolens 0, 2, 6, and 10% were used. The concentration of 0% was considered as control. The allelopathic effect has been studied on five weed species; Amaranthus retroflexus L., Portulaca oleracea L., Lolium multiflorum Lam., Sorghum halepense L., and Cuscuta campestris Yunck. The research also aimed to determine the effect of Stinkwort extract on the growth of tomato seedlings. All concentrations affected seed germination for all studied weeds. The concentration of 10% was more influential in growth-related indicators compared to other concentrations. The seeds of L. multiflorum and rhizomes of S. halepense were more tolerant to D. graveolens allelochemicals in germination rate than A. retroflexus, P. oleracea, and C. campestris. All concentrations led to a reduction in the weed heights and the wet and dry weights compared with the controls. The effect of the extract with various concentrations was catalytic for the growth of tomato seedlings, as the average height of tomato seedlings was in direct proportion to the concentration.

Las arvenses como hospedantes de microorganismos en un agroecosistema de sucesión Zea mays L.-Phaseolus vulgaris L.

La competencia entre las plantas arvenses y los cultivos es un tema de gran interés, ya que esta interacción puede causar grandes pérdidas en la agricultura. A pesar de algunos estudios en este tema, poco se sabe sobre la importancia de los microorganismos. Las plantas arvenses tienden a presentar interacciones positivas con la microbiota del suelo, mientras que los cultivos presentan interacciones neutras o negativas. La competición entre las plantas arvenses y los cultivos promueven cambios en la comunidad microbiana del suelo. El objetivo del presente trabajo fue determinar los microorganismos de mayor relevancia en la rizófora de las principales especies de arvenses colectadas en los cultivos de maíz y frijol sembrados en sucesión durante tres años. Sobre un suelo Ferralítico Rojo, se condujeron seis experimentos para conocer los posibles beneficios del manejo oportuno de las arvenses en los cultivos del maíz (Zea mays L.) y del frijol (Phaseolus vulgaris L.) en un sistema sucesional para lo cual se determinaron los cambios estructurales de las arvenses e influencia de estas, sobre la presencia de microorganismos. La especie dominante de arvense fue Sorghum halepense L. en ambos cultivos. Las relaciones interespecíficas arvenses-cultivos incrementaron la biodiversidad asociada al sistema productivo. Se registraron 31 especies de arvenses (15 en maíz y 16 en frijol). Amaranthus dubius L., S. halepense y Parthenium hysterophorus L. y junto a ellas, Eleusine indica L. y Lepidium virginicum L., albergaron la mayor cuantía de microorganismos en la rizósfera. del suelo, mientras que los cultivos presentan interacciones neutras o negativas. La competición entre las plantas arvenses y los cultivos promueven cambios en la comunidad microbiana del suelo. El objetivo del presente trabajo fue caracterizar los microorganismos de mayor relevancia en la rizófora de las principales especies de arvenses colectadas en los cultivos de maíz y frijol sembrados en sucesión durante tres años. Sobre un suelo Ferralítico Rojo, se condujeron seis experimentos para conocer los posibles beneficios del manejo oportuno de las arvenses en los cultivos del maíz (Zea mays L) y del frijol (Phaseolus vulgaris L) en un sistema sucesional para lo cual se determinó los cambios estructurales de las arvenses e influencia de éstas sobre la fertilidad presencia de microorganismos del suelo. La especie dominante de arvense fue Sorghum halepense (L.) en ambos cultivos. Las relaciones interespecíficas arvenses-cultivos incrementaron los nutrientes y la biodiversidad asociada al sistema productivo. Se registraron 31 especies de arvenses (15 en maíz y 16 en frijol). Amaranthus dubius Mart., Sorghum halepense (L.) y Parthenium hysterophorus (L.), y junto a ellas, Eleusine indica (L.) y Lepidium virginicum (L.), albergaron la mayor cuantía de microorganismos en la rizofera.

Fitness Costs Associated to an Ile2041Asn Mutation in the Geophyte Sorghum halepense Resistant to ACCase-Inhibiting Herbicides

Sorghum halepense (L.) Pers. is a troublesome weed of maize which reproduces through seeds and rhizomes. Resistance to ACCase-inhibiting herbicides due to a target-site mutation Ile-Asn in position 2041 of the ACCase gene was confirmed in several populations in Italy. The presence of fitness costs related to the allelic variant Ile2041Asn has never been investigated in ACCase-resistant S. halepense. Three growth analyses pot experiments were performed starting from rhizome buds (Exp1 and Exp3) or seed (Exp2). Plant development was monitored throughout the life cycle through destructive samplings. The mutation responsible for resistance to ACCase inhibitors was detected in all plants included in the experiments using a Cleaved Amplified Polymorphic Sequence method. Classical growth analysis was performed for the multiple sampling experiments (Exp1 and Exp2) and allometric relationships were calculated for the different dry weight plant parts in all experiments. Allometric relationships showed that susceptible (S) and ACCase resistant (R) biotypes allocated biomass differently in the reproductive structures: S populations allocated on average 30% more biomass in the panicles, whereas R populations allocated 12% more biomass to rhizomes than S populations. This was more evident when the experiments started from rhizomes buds. Reproductive allocation and reproductive effort were higher in S biotypes and R biotypes, respectively. The higher production of rhizomes and the lower production of seeds of the R biotype can significantly impact the evolution of herbicide resistance under continuous application of herbicides with the same mode of action. A medium-long term resistance management strategy which implements appropriate soil tillage and crop rotation taking into account the different reproductive attitude of biotypes S and R should be devised.

The Evolutionary Dynamics of Repetitive DNA and Its Impact on the Genome Diversification in the Genus Sorghum

Polyploidization is an evolutionary event leading to structural changes of the genome(s), particularly allopolyploidization, which combines different genomes of distinct species. The tetraploid species, Sorghum halepense, is assumed an allopolyploid species formed by hybridization between diploid S. bicolor and S. propinquum. The repeat profiles of S. bicolor, S. halepense, and their relatives were compared to elucidate the repeats’ role in shaping their genomes. The repeat frequencies and profiles of the three diploid accessions (S. bicolor, S. bicolor ssp. verticilliflorum, and S. bicolor var. technicum) and two tetraploid accessions (S. halepense) are similar. However, the polymorphic distribution of the subtelomeric satellites preferentially enriched in the tetraploid S. halepense indicates drastic genome rearrangements after the allopolyploidization event. Verified by CENH3 chromatin immunoprecipitation (ChIP)-sequencing and fluorescence in situ hybridization (FISH) analysis the centromeres of S. bicolor are mainly composed of the abundant satellite SorSat137 (CEN38) and diverse CRMs, Athila of Ty3_gypsy and Ty1_copia-SIRE long terminal repeat (LTR) retroelements. A similar centromere composition was found in S. halepense. The potential contribution of S. bicolor in the formation of tetraploid S. halepense is discussed.

Validation of Reference Genes for Quantitative PCR in Johnsongrass (Sorghum halepense L.) under Glyphosate Stress

Weeds are one of the main causes of the decrease in crop yields, with Johnsongrass (Sorghum halepense L.) being one of the most significant. Weeds can be controlled by herbicides, but some have developed resistance. Quantitative PCR is the technique of choice for studying gene expression related to herbicide resistance because of its high sensitivity and specificity, although its quantitative accuracy is highly dependent on the stability of the reference genes. Thus, in this study we evaluated the stability of different reference genes of glyphosate-resistant S. halepense. Nine genes frequently used as reference genes were selected: MDH, ADP, PP2A, EIF4α, ACT, ARI8, DnaJ, Hsp70, and ALS1, and their expression analyzed in susceptible and resistant biotypes at 0, 24 and 72 h post-application of glyphosate. The stability was analyzed with the geNorm, NormFinder, and BestKeeper software programs and using the ΔCt method. RefFinder was used to generate a comprehensive stability ranking. The results showed that PP2A and ARI8 were the most stable genes under the test conditions. EPSPS expression was also verified against the best two and the worst two reference genes. This study provides useful information for gene expression analysis under glyphosate stress and will facilitate resistance mechanism studies in this weed species.

Diversity of Grass Species from Sendhwa Dist. Barwani (M.P.), India

The present study was aimed to determining Diversity of grass species of Sendhwa Dist. Barwani, Madhya Pradesh, India. Sendhwa is bestowed with unique diversity of ethnic culture and natural resource. The present study is based on diversity of grass species in Satpura region of Sendhwa Dist. Barwani, of Madhya Pradesh, India during the period of 2017-2020. This area is the representative of climax vegetation and rich in grass biodiversity. On the basis of grass utility three species are abundantly found along with 38 genera and 45 species are frequently occurred in Sendhwa dist. Barwani. The data from the primary and secondary sources resulted in the documentation of 45 species belonging to 38 genera. The study area has a rich species diversity of grasses. Present study observes some wild economically important grasses which are Brachiaria reptans (L.) Gard. & Hubb., Echinochloa colonum (L.) Link., Oryza rufipogon Griff., Pennesetum pedicelatum Trin. , Phragmites karka (Retz.) trin ex. Steud., Sporobolus capillaries Miq., Sorghum halepense (L.) Kuntz., Urochloa panicoides P.Beauv. This documentation will be helpful to the staff of Forest department and for better management of grasslands with special reference to wildlife habitat.

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.

Diseases of S. halepense: Possible Role as a Reservoir of Pathogens to Other Plants

Johnsongrass [Sorghum halepense (L.) Pers.] is one of the most noxious weeds distributed around the world. Due to rapid growth, wide dissemination, seeds that can germinate after years in the soil and ability to spread via rhizomes, S. halepense is difficult to control. From a perspective of plant pathology, Johnsongrass is also a potential reservoir of pathogens that can eventually jump to other crops, especially corn (Zea mays L.) and sorghum [Sorghum bicolor (L.) Moench]. As one of the most problematic weeds, understanding S. halepense and its diseases can provide useful information concerning its role in diseases of agronomically important crops. An alternative consideration is that S. halepense may provide a source of genes for resistance to pathogens. While some studies have verified that pathogens isolated from S. halepense actually cause disease on host crops through cross inoculation, similarity of disease symptoms and pathogen morphology have been used for identity of the disease agent in most studies. Availability of DNA sequence information has greatly altered and improved pathogen identification, leading to significant changes in phylogenetic assignments. Reclassification of pathogens, especially fungi, raises new questions concerning the role of S. halepense as a disease reservoir. Our goals in this review are to pinpoint, where possible, diseases where S. halepense acts as a significant pathogen reservoir and to point out problem areas where further research is needed.

Sorghum halepense (Johnson grass).

S. halepense is a perennial grass which can be cultivated for fodder, but is also an extremely invasive weed with a worldwide distribution. Its extensive spreading rhizome and shoot system and high rate of seed production make it extremely invasive and difficult to eradicate. The species has a number of detrimental effects including: toxicity to grazing stock, fire risk during summer and competitive exclusion of other plants. It reduces soil fertility, acts as a host for crop pathogens and is a known allergen. It is regarded as a serious weed in 53 countries and in a wide range of field crops.