Boron (B) toxicity is an important abiotic stress that drastically damages agricultural production worldwide, mostly in arid regions. Several studies have reported large losses in wheat due to high B in arable land. The identification of different B-toxicity-tolerant wheat germplasm and using them in breeding programs to develop tolerant cultivars is a potential solution to B toxicity. However, tolerance to B toxicity in such germplasm largely relies on the molecular changes in plants under B toxicity at the transcriptome level. Thus, the aim of this study is to determine the transcriptomic response of the roots of a B-toxicity-tolerant Triticum zhukovskyi genotype, PI296968, grown in a highly toxic B environment (10 mM B) in comparison with a control (3.1 μM B) treatment. T. zhukovskyi is a hexaploid wheat species forming a separate lineage from the main wheat lineage and can be a good source of genes for various stresses. However, it has been hardly explored for tolerance to any abiotic stress condition. This study is the first in the literature reporting the B toxicity tolerance of a T. zhukovskyi genotype along with the molecular changes occurring in it under B toxicity as compared to the control treatment. In the present study, 5992 genes were found to be significantly differentially expressed, with 1679 and 4313 up- and down-regulated genes, respectively. A number of transcription factors and pathways were identified to be significantly involved in the B toxicity response of the T. zhukovskyi genotype. A total of 12582 novel transcripts were determined in the study, with 9238 and 3344 coding and noncoding transcripts, respectively. The results not only suggest several candidate genes that can be further studied to improve wheat tolerance to B toxicity in upcoming breeding programs, but also enhance the understanding of the regulatory and molecular processes behind the wheat response to B toxicity. Further experiments are suggested to functionally characterize the identified high-B-responsive genes to confirm their role in providing B toxicity tolerance to the plants.

The continuously changing environment has led to devastating effects on the normal growth and development of plants. This necessitates the understanding of different components that can be involved in alleviating these effects. In the last two decades, nitric oxide (NO) has been largely focused on as a molecule whose endogenous production and exogenous supply lead to several molecular and physiological changes in plants under stressed conditions. Although its role as a signaling molecule in endogenous production has been largely discussed, its function in dealing with contemporary abiotic stress conditions on exogenous supply remains comparatively less explored. There is growing evidence that NO plays a critical role in many physiological processes; however, there is debate about the exact mechanism(s) through which NO lessens abiotic stress on external supply. In this review, we discuss the studies that were focused on observing the effect of exogenous NO on different abiotic stresses including heavy metal stress, element deficiency or toxicity stress, salt stress, drought stress, ultraviolet radiation stress, waterlogging stress, and chilling stress. Though the positive effects of endogenous NO have been discussed in brief in different sections, the focus of the review is to discuss the effects of exogenous NO on plant grown under abiotic stresses. Deciphering the underlying mechanism of exogenous NO treatment may open up new ideas that can suggest the successful application of NO in agricultural regions to reduce the damaging influences of different abiotic stresses.

Wheat production losses due to boron (B) toxicity can be reduced by breeding and growing modern wheat cultivars with a greater tolerance to high B. However, breeding of tolerant genotypes is possible by identifying B-tolerant wheat genetic resources and understanding their underlying molecular mechanism. Triticum dicoccum, despite being one of the oldest cultivated wheat species, mostly remained neglected and has been less explored for its potential towards abiotic stresses. In this study, for the first time, we report a B-toxicity-tolerant T. dicoccum genotype, PI94655, and its transcriptomic response towards high-B treatment (10 mM B) using RNA sequencing and RT-qPCR. More than 450 genes were significantly differentially expressed in the shoots of PI94655 under high B. A total 3237 novel genes and 12,206 novel transcripts were determined in the study. AP2-EREBP, MYB, and C3H were the families with the highest percentages of differentially expressed transcription factors (TFs) under B toxicity. Interestingly, KEGG pathway photosynthesis–antenna proteins showed the most significant enrichment. The obtained results suggested potential candidate genes that can be focused on to improve wheat tolerance to high B in future breeding programs. These genes can be functionally characterized to elucidate their role in providing tolerance to high B.

Boron (B) is a crucial microelement for several biological processes in plants; however, it becomes hazardous when present in excess in the soil. B toxicity adversely affects the wheat yield all around the world, particularly in the arid and semiarid regions. Aegilops, the nearest wild wheat relatives, could be an efficient source to develop B toxicity tolerance in modern cultivars. However, to potentially utilize these species, it is necessary to understand the underlying mechanisms that are involved in providing them tolerance. Other than hampering cellular and physiological activities, high B inhibits the uptake of nutrients in wheat plants that lead to nutrients deficiency causing a hindered growth. Thus, it is crucial to determine the effect of B toxicity on nutrient uptake and finally, to understand the role of nutrient homeostasis in developing the adaptive mechanism in tolerant species. Unfortunately, none of the studies to date has explored the effect of high B supply on the nutrient uptake in B toxicity tolerant wild wheat species. In this study, we explored the effect of 1 mM B (toxic B), and 10 mM B (very toxic B) B on the nutrient uptake in 19 Aegilops genotypes differing in B tolerance in contrast to Bolal 2973, the familiar B tolerant genotype. The obtained outcomes suggested a significant association between the B toxicity tolerance and the level of nutrient uptake in different genotypes. The B toxicity tolerant genotypes, Ab2 (TGB 026219, A. biuncialis genotype) and Ac4 (TGB 000107, A. columnaris genotype) were clustered together in the nutrient homeostasis-based heat map. Though B toxicity mostly had an inhibitory effect on the uptake of nutrients in root-shoot tissues, the tolerant genotypes revealed an increase in nutrient uptake under B toxicity in contrast with Control. The study directs towards future research where the role of external supply of few nutrients in enhancing the B toxicity tolerance of susceptible genotypes can be studied. Moreover, the genotype-dependent variation in the nutrient profile of the studied Aegilops genotypes under high B suggested that increasing number of Aegilops germplasm should be screened for B toxicity tolerance for their successful inclusion in the pre-breeding programs focusing on this issue.

Tuz stresi altında makarnalık buğday çeşitlerinin çimlenme ve erken fide dönemini değerlendirmek amacıyla, farklı tuz (NaCI) konsantrasyonları (0, 3 ve 6 g L-1) ve 10 adet makarnalık buğday çeşidi (Altıntaş-95, Ç-1252, Dumlupınar, Eminbey, Kunduru-1149, Kızıltan-91, Mirzabey-2000, Soylu, Svevo, Türköz) ile bu araştırma yürütülmüştür. Çalışmada çimlenme ve fide gelişiminin bazı indeksleri hesaplanmış ve analiz edilmiştir. Tuz stresi çimlenme kapasitesini (ÇK) ve çimlenme indeksini (Çİ), önemli ölçüde azaltırken, stres indeksini (Sİ) artırmıştır. Fide büyümesi ve başlangıç canlılığı (İC) da tuz etkisiyle önemli ölçüde engellenmiştir. İncelenen özellikler bakımından, çeşitler arasında farklılıklar ortaya çıkmış olup Altıntaş-95 artan tuz dozlarından en az etkilenen çeşit olurken, Kızıltan-91 ve Svevo en çok etkilenen çeşitler olmuştur. Çeşitlere bağlı olarak, tuz stresi çimlenme kapasitesini azaltırken fide gelişimini de etkilemiştir. Araştırma sonucu elde edilen bulgulara göre ortamda bulunan tuzun, osmotik etkisi nedeniyle bitkilerin su alımını engelleyerek çimlenmeyi geciktirdiği ve yüksek tuz seviyesinin (6 g L-1 NaCl) bitkilerin hücresel yapılarına zarar verdiği bu nedenle de çimlenme ve fide gelişiminin etkilendiği gözlemlenmiştir. Bu bağlamda da buğday çeşitleri arasında belirgin bir ayrım yapma imkânı sağlayan ilk canlılık ve stres indeksinin, tuzluluğa karşı toleranslı bitki genotiplerini belirlemek için faydalı özellikler olduğu söylenebilir.

The domestication and breeding of wheat genotypes through the years has led to the loss in their genetic variation, making them more prone to different abiotic stresses. Boron (B) toxicity is one of the stresses decreasing the wheat cultivars’ yield in arid and semi-arid regions around the world. Wild wheat progenitors, such as Triticum urartu Thumanian ex Gandilyan, possess a broader gene pool that harbors several genes conferring tolerance to various biotic and abiotic stresses. Unfortunately, T. urartu is not well-explored at the molecular level for its tolerance towards B toxicity in soil. In this study, for the first time, we compared the transcriptomic changes in the leaves of a high B-tolerant T. urartu genotype, PI662222, grown in highly toxic B (10 mM B in the form of boric acid) with the ones grown in the control (3.1 μM B) treatment in hydroponic conditions. The obtained results suggest that several mechanisms are involved in regulating the response of the studied T. urartu genotype toward B toxicity. All the growth parameters of T. urartu genotype, including root–shoot length, root fresh weight, and root–shoot dry weight, were less affected by high boron (10 mM) as compared to the boron-tolerant bread wheat cultivar. With a significant differential expression of 654 genes, 441 and 213 genes of T. urartu genotype were down- and upregulated, respectively, in the PI662222 leaves in high B in comparison to the control treatment. While key upregulated genes included those encoding RNA polymerase beta subunit (chloroplast), ATP synthase subunit gamma, chloroplastic, 60S ribosomal protein, and RNA-binding protein 12-like, the main downregulated genes included those encoding photosystem II protein D, ribulose bisphosphate carboxylase small subunit, and peroxidase 2-like. Interestingly, both Gene Ontology enrichment and KEGG pathways emphasized the possible involvement of the genes related to the photosynthetic process and apparatus in the high B tolerance of the T. urartu genotype. The further functional characterization of the identified potential T. urartu genes will facilitate their utilization in crop improvement programs for B toxicity stress.