RESUMEN
These experiments were performed to study the effect of exogenous treatment with melatonin at 100 µM and seed treatment with Bacillus thuringiensis (106-8 CFU/cm3) on growth, physio-biochemical characters, antioxidant enzymes, and anatomical features of soybean plants cv. Giza 111 under drought conditions. The findings showed that leaves number, nodules number, branches number, relative water content (RWC), chlorophyll content, and maximum quantum efficiency of PSII (Fv/Fm) were significantly reduced in soybean under drought stress. In addition, anatomical structure of stems and leaves were negatively affected in stressed plants. Moreover, proline, electrolyte leakage (EL%) lipid peroxidation (MDA), superoxide (O2 ·-), hydrogen peroxide (H2O2), and antioxidant enzymes, such as catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD), were significantly increased under drought stress. However, application of melatonin or Bacillus caused an improvement in growth characters, such as branches number, and increased chlorophyll a and b content, RWC as well as Fv/Fm in drought stressed soybean plants. Furthermore, melatonin and Bacillus treatments showed a significant decrease in EL%, MDA, O2 ·- and H2O2, besides regulating the activity of antioxidant enzymes under drought stress. The stems and leaves anatomical structure, such as lamina thickness, lower and upper epidermis thickness, number of xylem vessels/bundle, stem diameter, xylem vessels diameter, and phloem thickness, were improved under drought conditions with melatonin and Bacillus treatments. Therefore, the outcomes of this investigation recommended the use of melatonin as foliar spray and Bacillus thuringiensis as seed treatment, which could regulate a number of stress-responsive mechanisms to protect the stressed soybean plants, improve their growth under drought stress.
RESUMEN
Eight wheat cultivars, Sakha-94, Giza-171, Sids-1, Sids-12, Sids-13, Shandweel-1, Misr-1, and Misr-2, were evaluated for leaf rust at the seedling and adult stages in the 2021 and 2022 seasons. Biochemical, histological, and genetic analyses were performed to determine the link between cultivars that were either sensitive or resistant to the disease. Misr-2 and Giza-171 cultivars had the highest levels of resistance to leaf rust races in 2021 (LTCGT, STSJT, and TTTST) and 2022 (MBGJT, TTTKS, and TTTTT) at the seedling stage. However, at the adult stage, Sakha-94, Giza-171, Misr-1, and Misr-2 cultivars had the highest levels of resistance; consequently, they had the lowest final disease severity and the lowest values of AUDPC. The correlation between the seedling reaction and adult reaction was non-significant, with values of 0.4401 and 0.4793 in the 2021 and 2022 seasons, respectively. Throughout the biochemical, histological, and genetic analyses, it was observed that catalase, peroxidase, and polyphenol oxidase activities significantly increased in the resistant cultivars. The discoloration of superoxide (O2-) and hydrogen peroxide (H2O2) significantly decreased in resistant and moderately resistant wheat cultivars (Sakha-94, Giza-171, Misr-1, and Misr-2); higher hydrogen peroxide (H2O2) and superoxide (O2-) levels were recorded for the susceptible cultivars compared to the resistant cultivars. Molecular markers proved that the Lr50 gene was detected in the resistant cultivars. Puccinia triticina infections negatively affected most histological characteristics of flag leaves, especially in susceptible cultivars. The thickness of the blade (µ), the thickness of the upper and lower epidermis (UE and LE), the thickness of mesophyll tissue (MT), and bundle length and width in the midrib were decreased in susceptible cultivars such as Sids-1, Sids-13, and Shandwel-1 compared with resistant cultivars.
Asunto(s)
Basidiomycota , Triticum , Triticum/genética , Triticum/microbiología , Antioxidantes , Peróxido de Hidrógeno , Superóxidos , Enfermedades de las Plantas/genética , Enfermedades de las Plantas/microbiologíaRESUMEN
Drought stress is among the major threats that affect negatively crop productivity in arid and semi-arid regions. Probably, application of some additives such as biochar and/or brassinosteroids could mitigate this stress; however, the mechanism beyond the interaction of these two applications is not well inspected. Accordingly, a greenhouse experiment was conducted on wheat (a strategic crop) grown under deficit irrigation levels (factor A) i.e., 35% of the water holding capacity (WHC) versus 75% of WHC for 35 days while considering the following additives, i.e., (1) biochar [BC, factor B, 0, 2%] and (2) the foliar application of 24-epibrassinolide [BR, factor C, 0 (control treatment, C), 1 (BR1) or 3 (BR2) µmol)]. All treatments were replicated trice and the obtained results were statistically analyzed via the analyses of variance. Also, heat-map conceits between measured variables were calculated using the Python software. Key results indicate that drought stress led to significant reductions in all studied vegetative growth parameters (root and shoot biomasses) and photosynthetic pigments (chlorophyll a, b and total contents) while raised the levels of oxidative stress indicators. However, with the application of BC and/or BR, significance increases occurred in the growth attributes of wheat plants, its photosynthetic pigments, especially the combined additions. They also upraised the levels of enzymatic and non-enzymatic antioxidants while decreased stress indicators. Furthermore, they increased calcium (Ca), phosphorus (P) and potassium (K) content within plants. It can therefore be deduced that the integral application of BR and BC is essential to mitigate drought stress in plants.