Plants under attack of herbivores can emit increased amounts of volatile compounds from their leaves. Similarly, mechanically-injured plants can emit volatile chemicals that differ both quantitatively and qualitatively from undamaged plants. In this experiment, mechanical injury increased the release of the secondary metabolites linalool (3,7-dimethyl-1,6-octadien-3-ol) and linalool oxide (5-ethenyltetrahydro-2-furanmethanol) by wheat plants. The amounts released varied significantly with injury type and the period of time after injury. The time interval for the volatile collection within the photophase also influenced the amount collected for each day. The increased emission of these compounds, as a result of injury, may be explained as a defense mechanism against wounding. The role of these plant volatiles can be further investigated in the context of plant response to mechanical injury, within the broader context of all types of injury.

The fumigation toxicity of Melaleuca alternifolia (Maid. & Betche) Cheel. (Myrtales: Myrtaceae) essential oil and its major fractions was studied under laboratory conditions against adults of Sitophilus oryzae L. (Coleoptera: Curculionidae) to protect wheat grains ( Triticum aestivum L.) (Poales: Poaceae) from this global pest that destroys the host plant during storage. By analyzing M. alternifolia essential oil (EO) using GC/MS terpinen-4-ol and γ-terpinene were detected as major components. In the fumigation toxicity, M. alternifolia EO showed the highest toxicity (LC50 = 0.31 μl · l–1 air), followed by terpinen-4-ol (LC ₅₀ = 23.65 μl · l–1 air) and γ-terpinene was the least toxic (LC ₅₀ = 43.55 μl · l–1 air). When tested for their insecticidal activities against S. oryzae in stored wheat, no progeny emerged after 3 months of treatment with M. alternifolia EO at 10 mg · g–1 or with terpinen-4-ol and γ-terpinene for 2 months. However, none of these compounds could protect wheat grain from damage throughout the entire study period (4 months). Interestingly, all tested compounds at the highest application rate did not show any phytotoxic effects after 4 months of storage.

Nutrient deficiency (ND) stands as a prominent environmental factor that significantly impacts global plant growth and productivity. While numerous methods have been employed for detecting nutrient deficiencies in plants, many of them are invasive, time-consuming, and costly. In contrast, chlorophyll fluorescence (ChlF) signals have emerged as a non-destructive tool for the identification of specific nutrient deficiencies, such as nitrogen (N), phosphorus (P), and potassium (K), across various plant species. In this pioneering study, ChlF measurements were employed for the first time to detect a combination of nutrient deficiencies, including deficiencies in nitrogen and phosphorus (–NP), nitrogen and potassium (–NK), potassium and phosphorus (–KP), and a complete NPK deficiency (–NPK). The experiment was conducted using wheat (Triticum aestivum) and maize ( Zea mays) plants, which were grown under controlled laboratory conditions. An optimal hydroponic system was established to facilitate eight experimental conditions, namely: control, –N, –P, –K, –NP, –NK, –KP, and –NPK. Measurements were systematically collected at two-day intervals over a span of 24 days. Our findings demonstrate that chlorophyll fluorescence signals can enable the differentiation of various nutrient deficiencies even prior to the onset of observable symptoms. Furthermore, the examination of chlorophyll fluorescence parameters enables us not only to identify a singular macronutrient deficiency but also to detect multiple macronutrient deficiencies concurrently in a plant.

Using in vitro androgenesis serves as a unique opportunity to produce doubled haploid (DH) plants in many species. More benefits of this biological phenomenon have kept these methods in the focus of fundamental research and crop breeding for decades. In common wheat (Triticum aestivum L.), in vitro anther culture is one of the most frequently applied DH plant production methods. The efficiency of in vitro wheat anther culture is influenced by many factors, such as the genotype, growing conditions, collection time, pre-treatments, and compositions of media and culture conditions. According to some critical review, the genotype dependency, low efficiency and albinism are mentioned as limitations of application of the anther culture method. However, some research groups have made significant efforts to diminish the effects of these bottlenecks. Due to the improvements, a well-established in vitro anther culture method can be an efficient tool in modern wheat breeding programs.

Bread wheat is a major food crop on a global scale. Stripe rust, caused by Puccinia striiformis f. sp. tritici, has become one of the largest biotic stresses and limitations for wheat production in the 21st century. Post 2000 races of the pathogen are more virulent and able to overcome the defense of previously resistant cultivars. Despite the availability of effective fungicides, genetic resistance is the most economical, effective, and environmentally friendly way to control the disease. There are two major types of resistance to stripe rust: all-stage seedling resistance (ASR) and adult-plant resistance (APR). Although both resistance types have negative and positive attributes, ASR generally is race-specific and frequently is defeated by new races, while APR has been shown to be race non-specific and durable over time. Finding genes with high levels of APR has been a major goal for wheat improvement over the past few decades. Recent advancements in molecular mapping and sequencing technologies provide a valuable framework for the discovery and validation of new sources of resistance. Here we report the discovery of a precise molecular marker for a highly durable type of APR – high-temperature adult-plant (HTAP) resistance locus in the wheat cultivar Louise. Using a Louise × Penawawa mapping population, coupled with data from survey sequences of the wheat genome, linkage mapping, and synteny analysis techniques, we developed an amplified polymorphic sequence (CAPS) marker LPHTAP2B on the short arm of wheat chromosome 2B, which cosegregates with the resistant phenotype. LPHTAP2B accounted for 62 and 58% of phenotypic variance of disease severity and infection type data, respectively. Although cloning of the LPHTAP2B region is needed to further understand its role in durable resistance, this marker will greatly facilitate incorporation of the HTAP gene into new wheat cultivars with durable resistance to stripe rust.

Although Syrian high-yielding wheat cultivars grown under Mediterranean conditions include acceptable levels of resistance to biotic constraints, little is known about their susceptibility to Fusarium head blight (FHB), a harmful disease of wheat cultivation worldwide. The capacity of 16 fungal isolates of four FHB species to confer the disease on spikes and spikelets of six widely grown old and modern Syrian durum and bread wheat cultivars with known in vitro quantitative resistance to FHB was evaluated. Quantitative traits were visually assessed using spray and point inoculations for determining disease development rates, disease incidence (DI) and disease severity (DS) under controlled conditions. Differences in pathogenicity and susceptibility among wheat cultivars were observed, emphasizing the need for breeders to include aggressive isolates or a mixture of isolates representative of the FHB diversity in their screenings for selection of disease resistant cultivars. Bread wheat cultivars showed lower levels of spike and spikelet damage than durum cultivars regardless of the date of cultivar release. Overall, the six wheat cultivars expressed acceptable resistance levels to initial fungal infection and fungal spread. Quantitative traits showed significant correlation with previous standardized area under disease progress curve (AUDPCstandard) data generated in vitro. Thus, the predictive ability of AUDPCstandard appears to be crucial in assessing pathogenicity and resistance in adult wheat plants under controlled conditions. While in the Mediterranean countries the risk of disease is progressively increasing, the preliminary data in this report adds to our knowledge about four FHB species pathogenicity on a Syrian scale, where the environment is quite similar to some Mediterranean wheat growing areas, and show that Syrian cultivars could be new resistant donors with favorable agronomical characteristics in FHB-wheat breeding programs.

Fusarium crown rot (FCR), caused by Fusarium culmorum (Wm.G.Sm) Sacc., is an important disease of wheat both in Iraq and other regions of wheat production worldwide. Changes in environmental conditions and cultural practices such as crop rotation generate stress on pathogen populations leading to the evolution of new strains that can tolerate more stressful environments. This study aimed to investigate the genetic diversity among isolates of F. culmorum in Iraq. Twenty-nine samples were collected from different regions of wheat cultivation in Iraq to investigate the pathogenicity and genetic diversity of F. culmorum using the repetitive extragenic palindromic (REP-PCR) technique. Among the 29 isolates of F. culmorum examined for pathogenicity, 96% were pathogenic to wheat at the seedling stage. The most aggressive isolate, from Baghdad, was IF 0021 at 0.890 on the FCR severity index. Three primer sets were used to assess the genotypic diversity via REP, ERIC and BOX elements. The amplicon sizes ranged from 200–800 bp for BOX-ERIC2, 110–1100 bp for ERIC-ERIC2 and 200–1300 bp for REP. A total of 410 markers were polymorphic, including 106 for BOX, 175 for ERIC and 129 for the REP. Genetic similarity was calculated by comparing markers according to minimum variance (Squared Euclidean). Clustering analysis generated two major groups, group 1 with two subgroups 1a and 1b with 5 and 12 isolates, respectively, and group 2 with two subgroups 2a and 2b with 3 and 9 isolates, respectively. This is the first study in this field that has been reported in Iraq.

Accumulation of LaCl3, a well-known Ca2+-channel blocker, can inhibit plant growth. However, the current understanding of its effects on gene expression is limited. In this paper, different concentrations of LaCl3 (0, 0.5, 1.0, 1.5, 2.0 mM) were used to treat germinated wheat ( Triticum aestivum L.) seeds for 24 h. The degree of root growth inhibition gradually increased with increasing LaCl3 concentration. qRT-PCR analysis revealed that the expression of several key genes related to the cell cycle process, such as pcna, mcm2, rdr and cyclin B, were significantly down-regulated. Further analysis of genomic DNA instability using Random Amplified Polymorphic DNA (RAPD) and methylation levels by Coupled Restriction Enzyme Digestion-Random Amplification (CRED-RA) analysis indicated a significant increase in genomic DNA polymorphisms and methylation levels. The results of this study verified that the reasons why LaCl3 treatment can inhibit the growth of wheat roots are as follows: interference in the normal progression of the cell cycle, induction of genomic DNA instability and increase in DNA methylation levels.