Enhanced Reproductive Thermotolerance of the Tomato high pigment 2 Mutant Is Associated With Increased Accumulation of Flavonols in Pollen

Climate change has created an environment where heat stress conditions are becoming more frequent as temperatures continue to raise in crop production areas around the world. This situation leads to decreased crop production due to plant sensitivity to heat stress. Reproductive success is critically dependent on plants’ ability to produce functional pollen grains, which are the most thermo-sensitive tissue. Flavonols are plant secondary metabolites known for their potent antioxidative activity, essential for male fertility in several species including tomato, and implicated in heat stress tolerance. Since flavonols are highly abundant in fruits of the tomato high pigment 2 (hp2) mutant, we tested the level of flavonols in pollen of this mutant, under the hypothesis that increased accumulation of flavonols would render pollen more tolerant to heat stress. Indeed, pollen from two alleles of the hp2 mutant was found to have flavonols levels increased by 18 and 280% compared with wild-type (WT) under moderate chronic heat stress (MCHS) conditions. This mutant produced on average 7.8-fold higher levels of viable pollen and displayed better germination competence under heat stress conditions. The percentage of fully seeded fruits and the number of seeds per fruit were maintained in the mutant under heat stress conditions while decreased in wild-type plants. Our results strongly suggest that increased concentrations of pollen flavonols enhance pollen thermotolerance and reproductive success under heat stress conditions. Thus, the high flavonols trait may help frame the model for improving crop resilience to heat stress.

Protective Reactions of Seedlings Against Systemic and Local Zearalenone Application to Tolerant and Sensitive Wheat Varieties – Epr Studies

BACKGROUNDAmong the environmental stressors, which oxidative action is currently widely studied, are mycotoxins. The aim of presented studies was to investigate the response of leaves of seedlings to zearalenone (ZEN) applied directly to leaves and to grains (indirectly) of tolerant and sensitive wheat cultivars.RESULTS Biochemical analyses of antioxidative activity were performed for chloroplasts and showed the similar decrease of this activity independently of plant sensitivity and the way of ZEN application. On the other hand, higher amounts of superoxide radicals (microscopic observation) were formed in leaves of plants grown from grains incubated in solution of ZEN and in sensitive variety. Electron paramagnetic resonance (EPR) studies showed that upon ZEN treatment larger amount of Mn - aqua complexes was formed in leaves of tolerant wheat cultivar than in those of sensitive one whereas the degradation of Fe-protein complexes occurred independently of the sensitivity of plant varieties. CONCLUSIONThe changes in the quantity of organic stable radicals, which were formed by stabilizing reactive oxygen species on biochemical macromolecules, pointed to the higher ability to their generation in leaf tissues subjected to foliar ZEN treatment indicating the important role of these radical species in protective mechanism mainly against direct toxin action. The way of activation the defense mechanisms depended on the method of applications toxin.

Effects of 24-Epibrassinolide, Bikinin, and Brassinazole on Barley Growth under Salinity Stress Are Genotype- and Dose-Dependent

Brassinosteroids (BRs) are involved in the regulation of many plant developmental processes and stress responses. In the presented study, we found a link between plant growth under salinity stress and sensitivity to 24-epibrassinolide (24-EBL, the most active phytohormone belonging to BRs), brassinazole (Brz) and bikinin (inhibitors of BR biosynthesis and signaling pathways, respectively). Plant sensitivity to treatment with active substances and salinity stress was genotype-dependent. Cv. Haruna Nijo was more responsive during the lamina joint inclination test, and improved shoot and root growth at lower concentrations of 24-EBL and bikinin under salinity stress, while cv. Golden Promise responded only to treatments of higher concentration. The use of Brz resulted in significant dose-dependent growth inhibition, greater for cv. Haruna Nijo. The results indicated that BR biosynthesis and/or signaling pathways take part in acclimation mechanisms, however, the regulation is complex and depends on internal (genotypic and tissue/organ sensitivity) and external factors (stress). Our results also confirmed that the lamina joint inclination test is a useful tool to define plant sensitivity to BRs, and to BR-dependent salinity stress. The test can be applied to manipulate the growth and stress responses of crops in agricultural practice or to select plants that are sensitive/tolerant to salinity stress in the plant breeding projects.

Enhanced reproductive thermotolerance is associated with increased accumulation of flavonols in pollen of the tomato high-pigment 2 mutant

SummaryClimate change has created an environment where heat stress conditions are becoming more frequent as temperatures continue to rise in crop production areas around the world. This situation leads to decreased crop production due to plant sensitivity to heat stress. Reproductive success is critically dependent on plants’ ability to produce functional pollen grains, which are the most thermo-sensitive tissue. Flavonols are plant secondary metabolites known for their potent antioxidative activity, essential for male fertility in several species including tomato, and implicated in heat stress tolerance. Since flavonols are highly abundant in fruits of the tomato high pigment-2 (hp2) mutant, we tested the level of flavonols in pollen of this mutant, under the hypothesis that increased accumulation of flavonols would render pollen more tolerant to heat stress. Indeed, pollen from three alleles of the hp2 mutant were found to have flavonols levels increased by 40% on average compared with wild-type under moderate chronic heat stress conditions. This mutant produced on average 7.8-fold higher levels of viable pollen and displayed better germination competence under heat stress conditions. The percentage of fully seeded fruits and the number of seeds per fruit were maintained in the mutant under heat stress conditions while decreased in wild-type plants. Our results strongly suggest that increased pollen flavonols content enhances pollen thermotolerance and reproductive success under heat stress conditions. Thus, the high flavonols trait may help frame the model for improving crop resilience to heat stress.

Decontamination methods of tanks to spray 2,4-D and dicamba and the effects of these herbicides on citrus and vegetable species

In agriculture, the development of plants resistant to 2,4-D and dicamba tends to result in increased use of these herbicides in agricultural areas and consequently increases the risk in susceptible species. The aims of the present study are to assess the effects of 2,4-D and dicamba on citrus (Citrus sinensis var. Pêra Rio), lettuce (Lactuca sativa var. Stella) and tomato (Lycopersicum esculentum var. Santa Clara) and determine the best method for spray tank decontamination after applying such herbicides. All the experiments followed a completely randomized design with five replications. To study the effects of 2,4-D and dicamba on sensitive plants, experiments were performed on the following cultivated species: citrus, lettuce and tomato. Each species was subjected to 2,4-D (D, 670 g a.i. ha-1) and dicamba (D, 560 g a.i. ha-1) applied at doses of 0 D, 1 D, 0.5 D, 0.12 D, 0.03 D, 0.007 D and 0.001 D (of commercial doses (Ds)). In another experiment, the following methods were adopted to clean tanks used to spray 2,4-D and dicamba at commercial doses: wash with water (1x), water (2x), water (3x), water + 96% alcohol (1:1), water + detergent (2.5%) or no washing. The tanks were filled with water after treatment. The young tomato plants were used as bioindicators. Regarding plant sensitivity, citrus plants exhibited low potential for suffering losses due to 2,4-D and dicamba drift. The plants tolerated a dose of 0.12 D for both herbicides. Lettuce and tomato were extremely sensitive to 2,4-D and dicamba. Lettuce tolerated 2,4-D at a dose of 0.007 D but showed phytotoxicity symptoms; the tolerated dicamba dose was 0.03 D. Only the 0.03 D dose of 2,4-D was tolerated by tomato. Although the tomato plants presented phytotoxicity symptoms, the tolerated dicamba dose was 0.007 D. For the tank cleaning experiment, the spray tank cleaning by thoroughly washing in water (2x) was the most appropriate method to clean tanks used to spray 2,4-D. Washing with water (2x, at a minimum), water + alcohol (1:1) or water + detergent was equally effective to clean tanks filled with dicamba. Therefore, the study shows that the application of 2,4-D and dicamba in areas close to young Citrus sinensis plants should be avoided given that vegetable species, such as lettuce and tomato, do not tolerate the minimum drift of these herbicides. Double washing with water would be the most economical and effective method of cleaning tanks used to house these herbicides.

THE LINE RICO IS THE EARLIEST MATURING ACCESSION IN THE VIR COLLECTION OF SPRING BREAD WHEAT

Background. To optimize the process of bread wheat breeding for earliness and environmental adaptability, searching for new source material is a crucial task. The ultra-early line Rico (k-65588) – Triticum aestivum var. erythrospermum Koern. – stands out among the bread wheat accessions from the VIR collection for its important adaptive features.Materials and methods. Spring wheat accessions with different speed of development were selected from the VIR collection for this study, along with the ultra-early lines Rifor 1 ... 10 (F6-7 Rico × Forlani Roberto k-42641) and Fori 1 ... 8 (k-65589 ... k-65596) (F4 Foton k-55696 × Rico). Their responses to a short 12-hour day were assessed. Vernalization conditions were 30 days at 3°C. The genetics of plant sensitivity to vernalization and photoperiods was studied using allele-specific primers for the genes Vrn-A1, Vrn-B1, Vrn-D1 and Ppd-D1.Results and conclusions. In the Northwest of Russia, the period from seeding to heading for Rico plants was 39.9 ± 1.49 days, or 14.8 ± 1.22 days less than for the released commercial wheat cultivars. Among the 8400 wheat accessions, studied by the Wheat Genetic Resources Department of VIR in this area from 1948 to 2018, the shortest period from germination to heading was observed in the line Rico: 29 (28–30) days. The absence of response to vernalization in Rico, Fori and Rifor lines was determined by the dominant alleles Vrn-A1, Vrn-B1 and Vrn-D1. Photoperiodism in Rico and partially in Rifor was controlled by at least two genes: Ppd-D1 and Ppd-B1. In the F2 population of Rico hybrids with 8 wheat accessions no transgression was observed beyond the limits of Rico‘s variation. The difference in the development rate between Rico and other wheat accessions is controlled by two or three non-allelic genes. Rifor lines can compete in productivity with commercialized wheat cultivars.

Variation Among Spring Wheat (Triticum aestivum L.) Genotypes in Response to the Drought Stress. II—Root System Structure

(1) Background: The study analyzed wheat morphological traits to assess the role of roots structure in the tolerance of drought and to recognize the mechanisms of root structure adjustment to dry soil environment. (2) Methods: Root-box and root-basket methods were applied to maintain an intact root system for analysis. (3) Results: Phenotypic differences among six genotypes with variable drought susceptibility index were found. Under drought, the resistant genotypes lowered their shoot-to-root ratio. Dry matter, number, length, and diameter of nodal and lateral roots were higher in drought-tolerant genotypes than in sensitive ones. The differences in the surface area of the roots were greater in the upper parts of the root system (in the soil layer between 0 and 15 cm) and resulted from the growth of roots of the tolerant plant at an angle of 0–30° and 30–60°. (4) Conclusions: Regulation of root bending in a more downward direction can be important but is not a priority in avoiding drought effects by tolerant plants. If this trait is reduced and accompanied by restricted root development in the upper part of the soil, it becomes a critical factor promoting plant sensitivity to water-limiting conditions.