Wild Wheat Research Articles

Whole-genome sequencing of multiple isolates of Puccinia triticina reveals asexual lineages evolving by recurrent mutations.

The wheat leaf rust fungus, Puccinia triticina Erikss., is a worldwide pathogen of tetraploid durum and hexaploid wheat. Many races of P. triticina differ for virulence to specific leaf rust resistance genes and are found in most wheat-growing regions of the world. Wheat cultivars with effective leaf rust resistance exert selection pressure on P. triticina populations for virulent race types. The objectives of this study were to examine whole-genome sequence data of 121 P. triticina isolates and to gain insight into race evolution. The collection included isolates comprising of many different race phenotypes collected worldwide from common and durum wheat. One isolate from wild wheat relative Aegilops speltoides and two from Ae. cylindrica were also included for comparison. Based on 121,907 informative variants identified relative to the reference Race 1-1 genome, isolates were clustered into 11 major lineages with 100% bootstrap support. The isolates were also grouped based on variation in 1311 predicted secreted protein genes. In gene-coding regions, all groups had high ratios of nonsynonymous to synonymous mutations and nonsense to readthrough mutations. Grouping of isolates based on two main variation principle components for either genome-wide variation or variation just within the secreted protein genes, indicated similar groupings. Variants were distributed across the entire genome, not just within the secreted protein genes. Our results suggest that recurrent mutation and selection play a major role in differentiation within the clonal lineages.

Survey of Drought-Associated TAWRKY2-D1 Gene Diversity in Bread Wheat and Wheat Relatives.

Recent advances in plant genomics revealed numerous factors related to drought tolerance, including a family of WRKY transcription factors. The aim of this study was to evaluate polymorphism of the TaWRKY2-D1 across a range of bread wheat cultivars, interspecific hybrids, and wild wheat relatives within the Triticum genus as a potential molecular target for marker-assistant selection. The initial sequencing of the TaWRKY2-D1 gene in six Ukrainian commercial cultivars detected some sequence variations along the ~ 1.8kb of gene promoter and the followed coding region composed of four exons and three introns. Based on the gained sequence information, five sets of primers covering different gene regions were designed to annotate theTaWRKY2-D1 genetic diversity in 202 wheat cultivars, including 77 accessions from the CIMMYT collection, 72 commercial varieties cultivated in Ukraine, and 53 hybrids and wild wheat species. The combination of developed DNA markers enabled effective and reproducible annotation of cultivars genetic diversity. The primers set targeting introns adjusted to the gene's exon 3, turned out to be the most informative for screening heterogeneity of the TaWRKY2-D1. The developed molecular markers represent effective, informative means for selecting drought tolerance germplasm donors to promote wheat breeding programs.

Genetic Resistance of Wheat towards Plant-Parasitic Nematodes: Current Status and Future Prospects

Plant-parasitic nematodes (PPNs) are one of the major biotic factors that cause significant yield losses in wheat-growing areas worldwide. The major PPN groups causing significant economic losses in wheat quantity and quality are cereal cyst nematodes (CCNs) and root-lesion nematodes (RLNs). Based on their wide distribution, pathogenicity, high occurrence in wheat cultivated areas, they are considered major threats to the global food supply. The economic loss caused by these destructive pathogens ranges from 10 to 100% depending on different agro-ecological conditions such as drought, heat stress, and cold stress. Multidisciplinary management practices are being implemented to manage cereal nematodes (CNs) that range from cultural to molecular strategies. Integration of wheat resistant varieties with appropriate agronomic practices is recognized as the safest and most practical, effective, and applicable management strategy. Nine resistance genes (Cre1–Cre9) to CCN are well- documented in the literature. CreR, CreV and CreZ genes are relatively recently characterized from wheat and confer resistance to CCNs. On the other hand, Rlnn1 is the only resistance gene characterized from wheat that is known to confer resistance towards RLNs. However, breeding for resistance to PPN has numerous challenges that originate from the narrow genetic diversity and difficulty in the process of transferring resistance gene(s) from the source to the target variety. A unique opportunity for wheat genetic improvement was provided due to the availability of genomic resources and the wheat worldwide germplasm collection which includes wild wheat germplasm. Moreover, the presence of several genome-wide association studies and genome editing technologies could also help for further improvement to enhance CNs resistance in wheat. This article provides the latest information regarding the progress made in the identification and characterization of resistance genes from different sources and its utility against both CCNs and RLNs, which will attract the attention of the scientific community and other relevant stakeholders.

Genome-wide identification and phylogenetic relationships of the Hsp70 gene family of Aegilops tauschii, wild emmer wheat (Triticum dicoccoides) and bread wheat (Triticum aestivum)

The online version contains supplementary material available at 10.1007/s13205-021-02639-5.

Transgenic expression of TaTLP1, a thaumatin-like protein gene, reduces susceptibility to common root rot and leaf rust in wheat

Thaumatin-like protein (TLP) plays an important role in combating plant pathogen infection. Common root rot caused by Bipolaris sorokiniana and leaf rust caused by Puccinia triticina (Pt) are major fungal diseases in wheat. The disease responses of TaTLP1-overexpressing transgenic lines (TaTLP1-OE) were evaluated after inoculation with each pathogen. The TaTLP1-OE lines had no apparent differences in tiller number and 1000-kernel weight from the wild type Jinan Wheat No. 1 (JW1), whereas resistance to leaf rust and common root rot was improved, resulting from activated peroxidase and β-1,3-glucanase after B. sorokiniana infection, and reactive oxygen species-related genes were upregulated in TaTLP1-OE lines after Pt infection. These results indicated that stable expression of TaTLP1 increased resistance against both diseases.

Molecular cloning and functional characterization of TaIRI9 gene in wheat (Triticum aestivum L.).

The vernalization of wheat is one of the important factors that determine the planting region, introduction and cultivation techniques of wheat. However, the known vernalization genes (molecular marker) cannot precisely distinguish the vernalization requirement of winter wheat cultivars. Therefore, it is important to explore new vernalization genes and elucidate the mechanism of vernalization regulation. To explore the gene network in the vernalization pathway, we screened TaIRI9 (ice recrystallization inhibitor protein) gene associated with the expression profile of vernalization treatment of winter wheat Jing 841. Overexpression of TaIRI9 in wild type wheat resulted in reduced plant height, increased tiller number and delayed heading days. After 4°C vernalization treatment for 30, 35, 45 or 50days, TaIRI9 overexpression lines showed increased vernalization requirement and delayed heading time than wild type, indicating that TaIRI9 may affect vernalization process of wheat. In addition, the expression of the TaIRI9 genes were analyzed in winter Jing 841, strong winter wheat cultivar Xindong 18 and ten recombinant inbred lines (RILs, Hussar×Yanzhan1). The data showed that the expression of TaIRI9 was positively associated with the requirement of vernalization. These results indicated that TaIRI9 regulates heading and flowering time in wheat by promoting VRN2 and inhibiting flowering promoter VRN1 and VRN3 and may be involved in wheat vernalization regulation pathway.

Intraspecific diversity of durum wheat (Triticum durum Desf.): a unif ied classif ication.

The Department of Wheat Genetic Resources of the All-Russian Research Institute of Plant Genetic Resources (VIR) had developed and published in 1979 a classification of the genus Triticum L., which is based on the genomic composition of species and the presence or absence of a number of main genes that govern the “classification” traits. The grounds have been laid by F. Körnicke and J. Percival, and supplemented by N.I. Vavilov and K.A. Flaksberger. The classification, which is most often referred to as the “Classification of Triticum by Dorofeev et al.”, belongs to a number of the main modern classifications of the genus. This is the world’s first standardized system that contains all known intraspecific (infraspecific) taxa of wild and cultivated wheat species. A detailed classification makes it possible to identify a wide variety of forms in the genus Triticum L. and its individual species, which is especially important for collections preserved in genetic seed banks. The use of the intraspecific classification of the genus Triticum L. greatly simplifies the identification of the VIR collection accessions introduced from various sources or checking accession identity after regeneration in the field. However, the direct use of such a voluminous classification meets several difficulties. Therefore, we propose a unified intraspecific classification of durum wheat, based on the description of only 16 main botanical varieties out of 131 described so far, which have complexes of morphological traits of the spike and kernel that occur most frequently in durum wheat collections. The remaining 115 botanical varieties, which have additional traits, get their name by the addition of the abbreviated Latin name of one or another additional trait to the main name. Having mastered this way of describing the morphological traits of accessions, any user can easily navigate oneself in the systematized intraspecific diversity of collections. The purpose of this work is to acquaint the reader with the intraspecific classification of durum wheat (Triticum durum Desf.) developed at VIR and to offer its simplified version, which is based on the identification of the main and additional morphological traits of the spike and kernel.

Imposing water deficit on modern and wild wheat collections to identify drought‐resilient genotypes

AbstractBreeding for drought tolerance is the most effective approach to mitigate drought effects. The prime goal of the current study was to identify potentially drought‐tolerant wheat (Triticum aestivum L.) genotypes. Therefore, an extensive collection of wheat genotypes (2,100) was evaluated under two water regimes, that is water deficit (WD, 50% ETc ‘crop Evapotranspiration’) and well‐watered (WW, 100% of ETc) across several environments in Egypt. The number of days to flowering (NDF), plant height (PH) and grain yield (GY) were recorded under both water regimes across environments. Additionally, three yield‐based drought indices and water‐use efficiency (WUE) were calculated for the top 30% yielding genotypes (that produced economical GY; 3.58 ton ha−1 for WD and 7.5 ton ha−1 for WW). The results indicated a significant effect for environments, water stress, and genotypes, as well as the second‐ and third‐order interactions across all traits. WD significantly reduced PH, NDF, and GY by 5.0 cm, 10.6 days and 50.0%, respectively. PH, NDF and GY were highly correlated. However, the direction and magnitude of correlation under normal conditions were different from those under WD. For example, under WW conditions, late flowering and taller genotypes tended to produce higher GY. In contrast, under WD, earlier and shorter wheat genotypes tended to produce higher GY. According to the drought tolerance index (DTI), 254 genotypes were considered drought tolerance (DTI > 1). Based on WUE, DTI and GY under WD, 80 genotypes outperformed the commercially grown Egyptian cultivars. Our results implied that the evaluated collection might be a valuable source not only for drought‐tolerant genotypes but also for highly yielding water‐efficient genotypes under favourable conditions in Egypt and similar geographic regions.

Evaluation of the susceptibility of modern, wild, ancestral, and mutational wheat lines to Septoria tritici blotch disease

AbstractGlobally, bread wheat production is threatened by fungal diseases, including the devastating disease Septoria tritici blotch (STB). Given the global importance of STB, and the difficulty in identifying novel sources of resistance to this disease, we screened a variety of wheat genotypes, including wild, ancestral, and mutagenized lines, for their STB response. This delineated a panel of wild wheat relatives and Watkins collection lines with exceptional resistance to a range of Zymoseptoria tritici isolates, some of which are highly virulent on modern, elite wheat varieties. Additionally, we characterized the STB susceptibility of 500 lines of the wheat cultivar Cadenza TILLING population and developed backcross derivatives of two TILLING lines that show dominant partial resistance to STB. These backcross lines are partially resistant to multiple isolates of Z. tritici, and, with the wild and ancestral lines identified, provide a useful reservoir of STB‐resistant germplasm for use in wheat breeding programmes.

Origin of host-specificity resistance genes of common wheat against non-adapted pathotypes of Pyricularia oryzae inferred from D-genome diversity in synthetic hexaploid wheat lines

Wheat resistance genes Rwt3 and Rwt4 constitute a host-specificity barrier against non-wheat pathotypes of the blast fungus, Pyricularia oryzae. To understand the origin of these host-specificity resistance genes, we examined their distribution in Aegilops tauschii, a wild wheat progenitor species with the D genome, using synthetic hexaploid lines derived from crosses between Triticum turgidum cv. Langdon and 54 Ae. tauschii accessions, which cover the native ranges and lineages of the species. Infection assays with transformants carrying their corresponding avirulence genes (PWT3 and PWT4) revealed different distribution patterns of the two resistance genes. Rwt3 was present in the TauL1 and TauL2 lineages with wider geographic distribution, while Rwt4 was mainly present in the TauL2 and TauL3 lineages with narrow geographic distribution. Rwt3 and Rwt4 co-occurred exclusively in a TauL2 sublineage that has been suggested to be a probable donor of the D genome to common wheat. This result suggests that Rwt3 and Rwt4 in common wheat is likely to have been derived from Ae. tauschii individual(s) carrying both genes and that the common ancestor of common wheat had both genes when it was established through amphidiploidization.

Take-All Disease: New Insights into an Important Wheat Root Pathogen.

Take-all disease, caused by the fungal root pathogen Gaeumannomyces tritici, is considered to be the most important root disease of wheat worldwide. Here we review the advances in take-all research over the last 15 years, focusing on the identification of new sources of genetic resistance in wheat relatives and the role of the microbiome in disease development. We also highlight recent breakthroughs in the molecular interactions between G. tritici and wheat, including genome and transcriptome analyses. These new findings will aid the development of novel control strategies against take-all disease. In light of this growing understanding, the G. tritici-wheat interaction could provide a model study system for root-infecting fungal pathogens of cereals.

Diversity of Leaf Cuticular Transpiration and Growth Traits in Field-Grown Wheat and Aegilops Genetic Resources

Plants are subjected to unregulated water loss from their surface by cuticular transpiration. Therefore, specific morphophysiological changes may occur during leaf development to eliminate water loss. This study aimed to examine the cuticular transpiration of 23 winter wheat genotypes and their wild-growing predecessors of the genus Aegilops, which were divided into three groups to demonstrate their diversity. The genotypes were sown in autumn and grown in regular field trials at the Research Institute of Plant Production in Piešťany, Slovakia. Cuticular transpiration and growth parameters were analyzed in the postanthesis growth stage. Gravimetric measurement of residual water loss was performed on detached leaves with a precisely measured leaf area. The lowest nonproductive transpiration values were observed in modern wheat genotypes, while higher cuticular transpiration was observed in a group of landraces. Aegilops species generally showed the highest cuticular transpiration with increased water loss, but the total water loss per plot was low due to the low leaf area of the wild wheat relatives. Some of the growth parameters showed a good correlation with cuticular transpiration (e.g., dry mass per plant), but direct relationships between leaf traits and cuticular transpiration were not observed. This study identified a high diversity in cuticular resistance to water loss in wheat and Aegilops accessions of different origins. The potential of identifying and exploiting genetic resources with favorable cuticular transpiration in crop breeding is discussed.

Conservation and trans-regulation of histone modification in the A and B subgenomes of polyploid wheat during domestication and ploidy transition

BackgroundPolyploidy has played a prominent role in the evolution of plants and many other eukaryotic lineages. However, how polyploid genomes adapt to the abrupt presence of two or more sets of chromosomes via genome regulation remains poorly understood. Here, we analyzed genome-wide histone modification and gene expression profiles in relation to domestication and ploidy transition in the A and B subgenomes of polyploid wheat.ResultsWe found that epigenetic modification patterns by two typical euchromatin histone markers, H3K4me3 and H3K27me3, for the great majority of homoeologous triad genes in A and B subgenomes were highly conserved between wild and domesticated tetraploid wheats and remained stable in the process of ploidy transitions from hexaploid to extracted tetraploid and then back to resynthesized hexaploid. However, a subset of genes was differentially modified during tetraploid and hexaploid wheat domestication and in response to ploidy transitions, and these genes were enriched for particular gene ontology (GO) terms. The extracted tetraploid wheat manifested higher overall histone modification levels than its hexaploid donor, and which were reversible and restored to normal levels in the resynthesized hexaploid. Further, while H3K4me3 marks were distally distributed along each chromosome and significantly correlated with subgenome expression as expected, H3K27me3 marks showed only a weak distal bias and did not show a significant correlation with gene expression.ConclusionsOur results reveal overall high stability of histone modification patterns in the A and B subgenomes of polyploid wheat during domestication and in the process of ploidy transitions. However, modification levels of a subset of functionally relevant genes in the A and B genomes were trans-regulated by the D genome in hexaploid wheat.

What Makes Bread and Durum Wheat Different?

Durum wheat (tetraploid) and bread wheat (hexaploid) are two closely related species with potentially different adaptation capacities and only a few distinct technological properties that make durum semolina and wheat flour more suitable for pasta, or bread and bakery products, respectively. Interspecific crosses and new breeding technologies now allow researchers to develop wheat lines with durum or bread quality features in either a tetraploid or hexaploid genetic background; such lines combine any technological properties of wheat with the different adaptation capacity expressed by tetraploid and hexaploid wheat genomes. Here, we discuss what makes bread and durum wheat different, consider their environmental adaptation capacity and the major quality-related genes that explain the different end-uses of semolina and bread flour and that could be targets for future wheat breeding programs.

Illustrated key to infraspecific taxa of Triticum durum Desf.

Classifications of the genus Triticum L. differ in approaches to the number and content of both intrageneric and infraspecific taxa. According to the «GrainTax» System, an on‑line source of information on the taxonomy of wheat, there are currently 7 main classifications of the genus Triticum L. These include a classification developed at the Department of Wheat Genetic Resources of VIR, which is referred to as the “Classification of Triticum by Dorofeev et al.” This is the world’s first standardized system that contains all known infraspecific taxa of wild and cultivated wheat species. A detailed classification makes it possible to identify a wide variety of forms when working with the genus Triticum L. and its individual species, which is especially important for collections preserved in genetic seed banks. In accordance with this system, durum wheat (T. durum Desf.) is regarded as a species that includes two subspecies, 131 botanical varieties and 42 forms united into six groups and three subgroups of varieties. The basis of the infraspecific system is made up of botanical varieties with a definite complex of morphological traits of the spike and kernel. The present work contains descriptions of each botanical variety and photographs of most of them.

Identification of methoxylchalcones produced in response to CuCl2 treatment and pathogen infection in barley

Changes in specialized metabolites were analyzed in barley (Hordeum vulgare) leaves treated with CuCl2 solution as an elicitor. LC-MS analysis of the CuCl2-treated leaves showed the induced accumulation of three compounds. Among them, two were purified by silica gel and ODS column chromatography and preparative HPLC and were identified as 2ʹ,3,4,4ʹ,6ʹ-pentamethoxychalcone and 2ʹ-hydroxy-3,4,4ʹ,6ʹ-tetramethoxychalcone by spectroscopic analyses. The remaining compound was determined as 12-oxo-phytodienoic acid (OPDA), a major oxylipin in plants, by comparing its spectrum and retention time from LC-MS/MS analysis with those of the authentic compound. The accumulation of these compounds was reproduced in leaves inoculated with Bipolaris sorokiniana, the causal agent of spot blotch of the Poaceae species. This inoculation increased the amounts of other oxylipins, including jasmonic acid (JA), JA-Ile, 9-oxooctadeca-10,12-dienoic acid (9-KODE), and 13-oxooctadeca-9,11-dienoic acid (13-KODE). The treatments of the barley leaves with JA and OPDA induced the accumulation of methoxylchalcones, but treatment with 9-KODE did not. These methoxylchalcones inhibited conidial germination of B. sorokiniana and Fusarium graminearum, thereby indicating that these compounds possessed antifungal activity. Consequently, they are considered to be involved in the chemical defense processes as phytoalexins in barley. Accumulation of methoxylchalcones in response to JA treatment was observed in all seven barley cultivars tested, but was not detected in other wild Hordeum species, wheat, and rice, thus indicating that their production was specific to cultivated barley.

Recovery Plan for Wheat Blast Caused by Magnaporthe oryzae Pathotype Triticum

Wheat blast is an explosive new fungal disease of wheat caused by an Magnaporthe oryzae (synonym of Pyricularia oryzae) host-adapted subpopulation, the M. oryzae Triticum pathotype (MoT). MoT has been found in South America, South Asia, and Africa, but not in the United States. Wheat blast caused by the MoT fungus was first reported in Brazil in 1985 and subsequently spread to Bolivia, Paraguay, and Argentina in the 1990s and 2000s. The disease first appeared in Bangladesh in 2016 and in Zambia in 2017. The MoT fungus is seedborne, and the most likely route for movement across oceans was though grain trade. Wheat head (spike) blast is the predominant form of the disease in the field, although foliar and stem blast also occurs. The disease has proven hard to control when weather conditions are conducive, often resulting in devastating yield and quality losses. The only currently effective resistance, contained in the 2NvS translocation from the wild wheat relative Aegilops ventricosa, confers partial resistance that is variable depending on the genetic background of the specific wheat variety. Fungicides are not fully effective in controlling wheat head blast if warm, humid weather occurs during the heading stage. A major disease management strategy in areas where the disease occurs involves timing the wheat planting date so that heading does not coincide with warm rainy weather. A climate suitability model for the United States indicates that all of U.S. soft red winter wheat and about half of the hard red winter wheat are at risk.

An overview of innovative developments from the scientific provision of plant selection to resistance to diseases and pests

The Institute of Plant Protection of NAAS developed methods of plant selection for resistance to major pathogens and assessment methodology the resistance of winter wheat, potatoes, clover and alfalfa to pests to create complex resistant varieties. Donors of potato resistance to cancer, Alternaria, Phomosis and cyst-forming nematodes were identified. Methods for determining the resistance of cereals to high and low temperatures were developed. A collection of the Aegilops biuncialis L. wild wheat samples as sources of new resistance genes to plant diseases and pests was compiled. The soft winter wheat resistance genes to diseases by DNA markers were identified at the Institute of Plant Production named after V. Ya. Yuriev. The V. M. Remeslo Myronivka Institute of Wheat formed a set of winter wheat cultivars with group and complex resistance to diseases and pests. The Institute of Oilseed Crops of NAAS established physiological and biochemical mechanisms of resistance of sunflower, soybean, crown flax to pathogens. Collections of sunflower lines based on complex resistance to sunflower broomrape, dry rot, downy mildew and soybean lines based on complex resistance to white rot and Anthracnose were also created. In the National Scientific Center "Institute of Agriculture of NAAS", the fodder lupine resistance to the most important pathogens was investi-gated. The Institute of Agriculture in the Carpathian Region of NAAS revealed the spring barley, oat, rape, fiber flax varieties and selection numbers resistant to basic diseases; and the Institute of Rice of NAAS – rice cultivars resistant to diseases and pest pathogens. The resistance to main phytophagous insects of the modern genotypes of hemp, fiber flax and crown flax was assessed by the Institute of Agriculture of the North-East of NAAS. The assessment method of breeding value for the initial material of the main vegetables on the basis of disease resistance was developed by the Institute of Vegetables and Melons Growing of NAAS. Scientists of the Institute of Agroecology and Environmental Management of NAAS and V. M. RemesloMyronivka Institute of Wheat of NAAS revealed the cucumber and barley resistance to viral diseases. Key words: crops, pests, pathogens, resistance, resistance gene, resistance source.

Полиморфизм генов ферментов антиоксидантной системы у культурных видов пшеницы и дикорастущих сородичей

Abstract. The purpose of the study. Investigation of the polymorphism of genes of superoxide dismutase (SOD) and amylase in cultivated wheat species and wild relatives, the possibility of using them as molecular genetic markers to assess the genetic diversity of wheat varieties. Methods. The objects of research were wheat varieties cultivated in different periods in Kazakhstan, distant relatives and wild wheat species. The material was kindly provided by the staff of the laboratory of the gene pool of the SPC ZH im. A.I. Baraev, and also obtained from the USDA genetic resource collections (http://wheat.pw.usda.gov/GG3), John Innes Center (Germplasm Resources Unit, BBSRC) (http://data.jic.bbsrc.ac.uk/cgi-bin/germplasm/cereals.asp), All-Russian Institute of Plant Industry named after N.I. Vavilov (VIR) (http://91.151.189.38/virdb). Isolation of total DNA from etiolated seedlings was performed using the CTAB method. Selection of primers for PCR amplification, in silico PCR, analysis of oligonucleotides, and multiple alignment of DNA sequences were performed using the FastPCR program (http://primerdigital.com/fastpcr.html). Bioinformatic analysis of candidate genes was carried out using the NCBI database (http://www.ncbi.nlm.nih.gov/gene), UniProt http://www.uniprot.org/uniprot), Ensembl Plants (http://plants.ensembl.org). Results. Analysis of genetic diversity based on the spectra of superoxide dismutase and amylase isoenzymes in cultivated wheat species and wild relatives cultivated in different breeding periods showed that the level of differentiation between the studied groups was quite high, most of the genetic diversity was revealed within the groups. The genetic diversity of modern wheat varieties has a lower number of polymorphic loci and effective alleles of storage proteins, SOD, and amylases genes in comparison with distant relatives and ancient varieties from the world collection. Practical significance. The study of the polymorphism of the gene families of superoxide dismutase and amylase will increase the efficiency of identification of varieties and hybrids, study of their heterogeneity and targeted selection of parental pairs for crosses.

Herbicidal potential of Aerva javanica to control wild oat in wheat crop

We investigated the phytotoxicity of desert cotton (Aerva javanica) extracts on wild oat and wheat. Aqueous extracts from A. javanica roots, leaves and inflorescences collected from Jeddah and Al-Baha regions, Saudi Arabia were used. Generally, the allelopathic potential of water extracts of A. javanica collected from Jeddah were more in inhibitory to wild oat germination and seedlings growth than those from Al-Baha. In both regions, root extracts were inhibitory to wild oat followed by leaves and inflorescences extracts. All test aqueous extracts of both regions did not inhibit the wheat germination or seedlings growth.Whreas, the wild oat germination was reduced by root extracts 58.62 %, 28.62 % leaves extracts : 32.72 %, 17.72 % and inflorescences extract 28.11 %, 12.13 % by in plants samples collected from Jeddah and Al-Baha, respectively. Wild oat radical length was inhibited by root extracts 53.27 %, 32.84 % leaves 42.35 %, 9.63 % and inflorescences extracts 22.64 %, 16.75 % in case of Jeddah and Al-Baha plants, respectively. In pot culture experiment, all treatments markedly reduced the plant dry weight and soluble carbohydrates, proteins and free amino acids contents in wild oat. The differences in the allelopathic potentials of studied A. javanica extracts were related to the qualitative variations in their phytochemicals constituents. Our results showed that A. javanica extracts could be safely used to control wild oat growth in wheat fields after more detsaled research..