Response of Rice Genotype to Straighthead Disease as Influenced by Arsenic Level and Water Management Practices in Soil

Authors: HUA, BIN - LINCOLN UNIVERSITY OF MISSOURI; YAN, WENGUI; YANG, JOHN - LINCOLN UNIVERSITY OF MISSOURI

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/13/2012
Publication Date: 2/1/2013
Citation: Hua, B., Yan, W., Yang, J. 2013. Response of rice genotype to straighthead disease as influenced by arsenic level and water management practices in soil. Science of the Total Environment. 442:432-436.

Interpretive Summary: Straighthead is a physiological disease that occurs under certain soil conditions where rice is grown. Symptoms of the disease include seed heads that are empty of grain and remain erect at maturity. The symptoms can be induced when high levels of an arsenic (As) based herbicide is applied at planting. In addition, although As is toxic to plants, rice is able to accumulate As in the grain when grown under flooded, anaerobic conditions. Arsenic is known as a potential carcinogen and threat to human health via intake of elevated As from water and food. In an effort to minimize As uptake as well as As accumulation in rice grain and determine the susceptibility of rice cultivars to soil applied As, field experiments were conducted on three cultivars grown with two levels of soil As under continuous or intermittent flood water management practices. Results indicated that the grain yields and straighthead response were cultivar-dependent and influenced by soil As content and irrigation practices. Our study demonstrated that high levels of soil As induced straighthead disease, resulted in a dramatic yield reduction and elevated As accumulation in rice grain. The intermittent flood practice mitigated the negative impacts from high levels of soil As and was associated with the formation of iron (hydr) oxide that tends to immobilize soil As and lower As availability for rice plants. Therefore, the occurrence of rice straighthead disease, arsenic accumulation in grains, and grain yield reduction as a result of elevated As in soil could be effectively prevented and mitigated through an appropriate selection of As-resistant cultivars and intermittent flood water management.

Technical Abstract: Arsenic (As) uptake by rice plants and straighthead disease induced by As based herbicide are of concern to rice production. Bioavailability or mobility of inorganic As in soil has been reported being significantly influenced by soil minerals such as iron (hydr) oxide, however, the interactions of organic As such as monosodium methanearsonate (MSMA) with soil minerals are largely unknown. In an effort to minimize As uptake and determine cultivar response to soil As level, field experiments were conducted on three cultivars grown in both MSMA-treated and –untreated soils and under continuous or intermittent flood water management practices. Results indicated that the grain yields associated with straighthead were cultivar-dependent and influenced by soil As level and irrigation practices. The straighthead resistant cultivar yielded more and had lower grain As than the susceptible ones. Elevated soil As with continuous flood significantly reduced grain yield of susceptible cultivars by >89% due to substantially increased straighthead and had increased As content in grains. Yield reduction from the MSMA application could be partially mitigated with intermittent flood irrigation practice. The As uptake or accumulation was found to be associated with soil iron redox transformation influenced by the water management. This study demonstrates that the selection of less As-susceptible cultivars and intermittent flood irrigation practice could be effective means to lower the As accumulation in grains and minimize the occurrence of the As-induced straighthead-like symptoms and yield reduction.