Priming winter wheat seeds with the bacterial quorum sensing signal N-hexanoyl-L-homoserine lactone (C6-HSL) shows potential to improve plant growth and seed yield

Several model plants are known to respond to bacterial quorum sensing molecules with altered root growth and gene expression patterns and induced resistance to plant pathogens. These compounds may represent novel elicitors that could be applied as seed primers to enhance cereal crop resistance to pathogens and abiotic stress and to improve yields. We investigated whether the acyl-homoserine lactone N-hexanoyl-L-homoserine lactone (C6-HSL) impacted winter wheat (Triticum aestivum L.) seed germination, plant development and productivity, using two Ukrainian varieties, Volodarka and Yatran 60, in both in vitro experiments and field trials. In vitro germination experiments indicated that C6-HSL seed priming had a small but significant positive impact on germination levels (1.2x increase, p < 0.0001), coleoptile and radicle development (1.4x increase, p < 0.0001). Field trials over two growing seasons (2015-16 and 2016-17) also demonstrated significant improvements in biomass at the tillering stage (1.4x increase, p < 0.0001), and crop structure and productivity at maturity including grain yield (1.4 – 1.5x increase, p < 0.0007) and quality (1.3x increase in good grain, p < 0.0001). In some cases variety effects were observed (p ≤ 0.05) suggesting that the effect of C6-HSL seed priming might depend on plant genetics, and some benefits of priming were also evident in F1 plants grown from seeds collected the previous season (p ≤ 0.05). These field-scale findings suggest that bacterial acyl-homoserine lactones such as C6-HSL could be used to improve cereal crop growth and yield and reduce reliance on fungicides and fertilisers to combat pathogens and stress

Changes in hormonal status of winter wheat (Triticum aestivum L.) and spelt wheat (Triticum spelta L.) after heat stress and in recovery period

The dynamics and distribution of endogenous cytokinins (CKs), gibberellic (GA3) and salicylic (SA) acids in wheat (Triticum aestivum L., ‘Podolyanka’) and spelt wheat (Triticum spelta L., ‘Frankenkorn’) plants was analyzed using HPLC–MS. Fourteen-day-old plants that had been exposed to short-term heat stress (+ 40 °C, 2 h) and 21-day-old plants after recovery were studied. Heat stress induced rapid changes, both specific and nonspecific, in hormone levels and distribution. The level of GA3 decreased in the shoots and roots of both winter and spelt wheat. A reduction in SA content was observed in wheat, while an increase was observed in spelt. The pool of CKs significantly increased in wheat, while in spelt—it decreased more than twofold. After recovery, an increase in GA3 content occurred in both species, but not to the levels measured in control plants. More active accumulation of GA3 was observed in the roots. The content of SA in the shoots of wheat continued to decrease, while in the roots it increased. In spelt, hormone concentration decreased, but it remained higher than in 21-day-old control plants. In shoots of both plants the pool of CKs decreased, while in wheat roots it did not change, and in spelt roots it decreased. The total CKs content in stressed wheat plants was twice as high as in spelt. In general, we established significant hormonal fluctuations, which indicate a direct involvement of endogenous cytokinins, gibberellic and salicylic acids in wheat and spelt response to heat stress. Screening of stress-resistant genotypes of cereals may benefit from quantitation of CKs, GA3, and SA

The effects of moderate soil drought on phytohormonal balance of Triticum aestivum L. and Triticum spelta L.

Soil drought, which is one of the most threatening abiotic plant stressors, negatively impacts plant growth and yields. Plant phytohormones play a key role in the formation of plant responses to stress. We investigated the effect of moderate soil drought, created in controlled laboratory conditions on plant growth and peculiarities of endogenous abscisic (ABA), indole-3-acetic (IAA), gibberellic (GA3) and salicylic (SA) acids and cytokinins (CKs) accumulation in organs of two closely related wheat species: Triticum aestivum and T. spelta. We demonstrated that following the cessation of watering (within four days), shoots and roots of 18-day-old plants of both species accumulated ABA and SA, while the level of GA3 and IAA decreased. Pool of CKs significantly increased in roots and decreased in shoots. On day 21 following recovery, an increase in ABA content occurred in wheat shoots and roots and spelt shoots. IAA level increased in both species, but not to the levels measured in control plants. The highest level of GA3 was present in wheat roots. While the content of SA in wheat was at control level, spelt SA levels significantly exceeded the controls. There were complex changes in CKs pool, the nature of which depended on the species and plant organ. We propose that specific alterations in the nature of accumulation, localization, and balance between certain classes of phytohormones in wheat and spelt organs under the action of moderate soil drought are one of the main factors in systemic response to stress and the formation of an adaptation strategy