Effect of arbuscular mycorrhizal fungi, selenium, and biochar on photysynthetic pigments and antioxidant enzyme activity under arsenic stress in mung bean (Vigna radiata)

Authors: ALAM, MD ZAHANGEER - Bangladesh Agricultural Research Institute; McGee, Rebecca; HOQUE, MD ANAMUL - Bangladesh Agricultural University; AHAMMED, GOLAM JALAL - Henan Normal University; CARPENTER-BOGGS, LYNNE - Washington State University

Submitted to: Frontiers in Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/15/2019
Publication Date: 3/12/2019
Citation: Alam, M., Mcgee, R.J., Hoque, M., Ahammed, G., Carpenter-Boggs, L. 2019. Effect of arbuscular mycorrhizal fungi, selenium, and biochar on photysynthetic pigments and antioxidant enzyme activity under arsenic stress in mung bean (Vigna radiata). Frontiers in Physiology. https://doi.org/10.3389/fphys.2019.00193.
DOI: https://doi.org/10.3389/fphys.2019.00193

Interpretive Summary: Human health faces global risks due to micronutrient malnutrition. Nutrition for human beings depends on availability, accessibility, and utilization of quality foods. Mung bean is a high-quality pulse crop with high nutritional value. This crop is able to fix nitrogen, which has a positive impact on soil fertility and productivity in subsequent crops. In addition, mung bean is an important source of protein, with twice the amount on average compared with cereal grains. Currently, mung bean cultivation is affected by several environmental stresses that cause enormous yield losses every year. Arsenic contamination is one of the main abiotic stresses that limit plant growth and leads to the deterioration of food quality by its entry into the food chain. Over the last several decades, severity of As stress has increased to become a global problem for the cultivation of various food crops. Arsenic is a toxic and carcinogenic element that occurs widely in soil environments around the world. This metal has severe effects on seedling growth, root growth and various physiological properties of plants. Recently, biochar soil amendment has been reported to reduce arsenic uptake and toxicity in plants, inoculation with arbuscular mycorrhizal fungi has been shown to reduce plant stress, and adding selenium to soil has been shown to increase plant growth. In this study, we applied biochar, arbuscular mycorrhizal fungi and selenium to soils contaminated with arsenic and evaluated the changes in biochemical coumpounds in six mung bean cultivars with the ultimate goal of identifying possible bioremediation actions. We found that all three stress relief substances were effective at increasing the chlorophyll content and activity of catalase, an enzyme important in protecting cells from damage, and in reducing the proline content, which is an indicator of osmotic stress. We conclude that all three substances are highly effective agains arsenic stress and can be used to reduce arsenic-induced stress in mung bean.

Technical Abstract: Environmental perturbations alter biochemical compounds in food crops. Arsenic (As), a toxic metalloid, is known to affect the cultivation of food crops in many regions of the world. However, changes in chlorophyll, catalase (CAT), and proline in response to As stress and the role of stress relief substances remain largely unknown in mung bean (Vigna radiata L.). In this study, biochar (BC), arbuscular mycorrhizal fungi (AMF), and selenium (Se) were applied to soils as stress relief substances (under 30 mg kg-1 As stress), and the effects of BC, AMF, and Se on chlorophyll a, chlorophyll b, total chlorophyll, CAT activity, and proline content were studied in different mung bean genotypes. Under As stress, the chlorophyll a, chlorophyll b, and total chlorophyll contents in BARI mung 3, BARI mung 5, and BARI mung 8 were statistically similar. CAT activity increased in comparison to the control due to the application of BC, AMF, and Se in mung bean crops. However, the amount of proline was significantly lower in AMF, BC, and Se-treated mung bean. This indicates that oxidative stress was potentially minimized in As-stressed mung bean crops due to application of these stress relief substances. Notably, AMF was relatively effective against As stress in comparison to BC and Se. It is concluded that BC, AMF, and Se are all highly effective in enhancing antioxidant defenses as well as the nutritional quality of mung bean crops under As stress.