Lowland rice (Oryza sativa L.) encounters flooded soils that are anaerobic and chemically reduced. Exposure of the roots to high soil Fe2+ concentrations can result in toxicity. Internal aeration delivering O2 to submerged roots via the aerenchyma is well understood, but the effect of Fe2+ on O2 transport in roots is less studied. We aimed to evaluate the effects of Fe2+ on growth and root aeration. O. sativa var. Amaroo was grown in aerobic and deoxygenated solutions with 0 mM, 0.18 mM, 0.36 mM, 0.54 mM or 0.72 mM Fe2+ using FeSO4.7H2O and a control with 0.05 mM Fe-EDTA. The treatments were imposed on 14-day-old plants (28–30 days old when harvested). Dry mass, shoot Fe concentration, root porosity and patterns of radial O2 loss (ROL) along roots were determined. In the aerobic solution, where Fe2+ was oxidised in the bulk medium, root dry mass increased with higher Fe2+; this was not the case in stagnant solutions, which had no significant root growth response, although Fe oxidation near the root surface was visible as a precipitate. In the highest Fe2+ treatment, shoot Fe concentrations in aerobic (667 mg kg–1) and stagnant (433 mg kg–1) solutions were below the level for toxicity (700 mg kg–1). Rice responded to high Fe2+ in aerobic conditions by increasing root porosity and inducing strong barriers to ROL. In stagnant conditions, root porosity was already high and the ROL barrier induced, so these root aeration traits were not further influenced by the Fe2+ concentrations applied.
Abstract:Rice is the main staple crop for one-third of the world population. To maximize yields, large quantities and constant input of fertilizers containing essential nutrients such as phosphorus (P) and iron (Fe) are added. Rice can germinate in both aerobic and anaerobic conditions, but the crosstalk between oxygen (O 2 ) and nutrients such as P and Fe on plant growth remains obscure. The aim of this work was to test whether such interactions exist, and, if so, if they are conserved between up-and lowland rice varieties. To do so, we assessed shoot and root biomass as well as inorganic phosphate (Pi) accumulation in four rice varieties, including two lowland rice varieties Nipponbare and Suphanburi 1 (SPR1) (adapted to non-aerated condition) and two upland rice varieties CMU122 and Sew Mae Jun (SMJ) (adapted to aerated condition) under various conditions of Pi and/or Fe deficiencies, in aerated and non-areated solution. Under these different experimental conditions, our results revealed that the altered shoot biomass in Nipponbare and SPR1 was O 2 -dependent but to a lesser extent in CMU122 and SMJ cultivars. In this perspective, discovering the biological significance and molecular basis of these mineral elements and O 2 signal interaction is needed to fully appreciate the performance of plants to multiple environmental changes.
Flash floods occur in rainfed lowland and flood-prone areas and have a profound incidence on crop yield, which is tightly linked to worldwide food insecurity. The most flooding-threatened crop is rice. Under this condition, rice undergoes anoxic and post-anoxic shock that affects its growth, development capacity and ultimately causes an important grain yield loss. Therefore, the introduction of submergence-tolerant varieties in a flood-prone area was proposed as a preventive solution to limit these effects. Such a solution presents room for improvement and would benefit from a post-submergence management to ensure a better rice yield, yet remains to be defined. In this study, we assessed the effect of flooding on growth and yield of different rice varieties submerged at a different time of their developmental stage. We compared three rice varieties, namely Prachinburi 2 (PCR2), Kao Samer 1 (KSM1) and Neang Guang 5 (NG5), for their tolerance to 14 days of 50 cm depth submergence at 30, 60 and 90 Days After Germination (DAG). At 30 DAG, the recovery ability of KSM1 was restricted, showing decreased shoot dry mass and grain yield, whereas photo assimilate transport of PCR2 and NG5 was altered, resulting in high leaf nitrogen (N) concentration but low grain yield. Our data revealed that rice varieties were more tolerant to submergence at 60 and 90 DAG. In opposition to KSM1 and NG5 grain yield, PCR2 showed rapid recovery with a marked increase of shoot dry mass and grain yield. Taken together, our result indicates that de-submergence at late developmental stage promotes rice recovery and yield of tolerant variety. Gene discovery work is required to identify molecular players and pathways that are involved in submergence stress recovery in rice.
Pathogens associated with Chinese kale leaf spot disease were recovered from necrotic lesions on the Chinese kale leaves and identified as Alternaria brassicicola (Schw.) Wiltshire. This disease is one of the most significant destructive pathogens to vegetable crops in Thailand and Southeast Asia. Disease management of these pathogens is done by using synthetic fungicides which are expensive and harmful to the environment. This study aimed to investigate the efficacy of the extracts from five plants, Hydnocarpus anthelminthicus Pierre ex Laness., Crateva magna (Lour.) DC., Caesalpinia sappan L.,Xanthophyllum lanceatum J. J. Sm., and Carallia brachiata (Lour.) Merr. to control the Chinese kale leaf spots caused by A. brassicicola in in vivo condition. In an in vivo test, we found that the plant extracts of C. brachiata, H. anthelminthicus, X. lanceatum and C. magna showed a potential in control efficacy against brassica dark leaf spots caused by A. brassicicola. The four plant extracts effectively suppressed the development of leaf spots at a concentration of 10,000 ppm and 50,000 ppm at 30 DAT. However, at 40 DAT the C. magna and H. anthelminthicus extracts strongly inhibited A. brassicicola at concentrations of 10,000 ppm and 50,000 ppm respectively when compared with the water control. This is the first report demonstrating that the plant extracts collected from riparian forest can provide control against brassica dark leaf spots disease. Based on our study, we demonstrated that the ability of plant crude extracts can be used as natural fungicides to control Chinese kale leaf spots and replace synthetic fungicide.
Background: Rice brown spot disease is caused by the fungus Bipolaris oryzae (Breda de Haan), which is one of the most significantly devastating diseases in rice. Nowadays, biological control agents and plant extracts as botanical fungicides are used to develop an alternative method to control this disease and reduce the use of synthetic fungicides. Therefore, the efficacy levels of Hydnocarpus anthelminthicus Pierre ex Laness., Crateva magna (Lour.) DC., Caesalpinia sappan L., Xanthophyllum lanceatum J. J. Sm. and Carallia brachiata (Lour.) Merr. crude extracts were tested in vitro against B. oryzae and their control of rice brown spot disease under greenhouse conditions. Methods: Five plants namely; H. anthelminthicus, C. magna, C. sappan, X. lanceatum and C. brachiata were cleaned with tap water and air dried at 28±2°C then cut into small pieces and ground into fine powder and stored at 4°C until used. Plant crude extracts was prepared using ethanol as solvent. Result: The results showed that the H. anthelminthicus crude extract showed the best antifungal activity against B. oryzae at the highest dose tested, causing 93% mycelial growth inhibition. Under greenhouse testing, the application of the H. anthelminthicus, X. lanceatum, C. brachiata, C. magna and C. sappan crude extracts at a concentration of 50,000 ppm effectively suppressed and reduced rice brown spot incidence caused by B. oryzae when applied once 30 days after transplanting (DAT). Interestingly, the H. anthelminthicus crude extract at a concentration of 10,000 ppm displayed the greatest suppression of the development of rice brown spot disease in terms of disease incidence when applied twice 30 DAT and 45 DAT compared with unprotected control. The results of this study indicated that H. anthelminthicus could provide botanical fungicide protection against rice brown spot disease to reduce the use of synthetic fungicides.
Background: Alternaria brassicicola (Schw.) causes black spot disease, which is one of the major diseases limiting the production of vegetable crops, especially Chinese kale in Southeast Asia and Thailand. Previous pathogen management based on synthetic fungicides is expensive, toxic for humans, and harmful to the environment. The current study investigated the efficiency of Talaromyces flavus (Klöcker) Stolk and Samson Bodhi001, Talaromyces trachyspermus (Shear) Stolk and Samson Bodhi002, Talaromyces flavus (Klöcker) Stolk and Samson Bodhi003, Neosartorya fischeri (Wehmer) Malloch and Cain Bodhi004, and Neosartorya fischeri (Wehmer) Malloch and Cain in controlling Chinese kale black spot disease caused by A. brassicicola under field conditions. Methods: A. brassicicola and four antagonistic fungus strains were cultured separately on a PDA plate and incubated at room temperature for 14 days. Ten mL of sterile water was poured into a culture plate, and the spores were gently scraped from the mycelium with a sterile loop to obtain a spore suspension and afterward adjusted to a final concentration of 106 spores mL−1. Result: The results showed that spore suspensions of 106 spores mL−1 of T. flavus Bodhi001, T. trachyspermus Bodhi002, T. flavus Bodhi003, N. fischeri Bodhi004, and N. fischeri effectively controlled black spot disease in field trials and resulted in a significant reduction in black spot incidence compared with the unprotected control. Meanwhile, the spore suspension of T. flavus Bodhi001 revealed the greatest suppression of black spot incidence, causing 10.23% and 42.93% disease reduction, compared with the negative control, indicating promising preventive activity against A. brassicicola. Based on our results, T. favus Bodhi001 is a promising biological control agent (BCA) in controlling A. brassicicola causing Chinese kale black spot disease.
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