Special Summer Workshop: Searching for the Means of Coexistence: From Experiences and Ideas Across the Globe

High yielding crop production technologies became available for farmers in irrigated favorable agricultural ecosystems from 1960’s known as Green Revolution, while 77% of world arable land (~1,086Mha in 2014, FAOSTAT) is estimated without irrigation and prone to water shortage or drought (a disaster from a shortage of rainfall and available water on agriculture and other human lives). Greater differences in productivity between favorable and marginal agricultural ecosystems may increase economic gaps in society and disturb co-existence of farmers in different regions of the world. Crop scientists had put their efforts to increase yield stability and resistance to the stress under rainfed marginal environments since 1970’s by adopting various approaches including molecular biology. Deep and thick roots are considered as important for rice adaptation to drought, but root thickness was less studied than deep rooting, partly due to difficulty in field phenotyping. Thicker roots with wider stele transversal areas and larger xylem diameters and numbers may improve hydraulic conductivity leading to superior growth under drought. Recently, a genomic region to increase “thickness of stele and root” called Stele Transversal Area 1 (Sta1) was found in rice under greenhouse experiment, but its yield advantage has not been reported. This study evaluated the effects of Sta1 on root thickness traits and grain yield both greenhouse and field experiments in Nishitokyo. Root thickness-related traits are to be quantified by carefully identifying individual roots (i.e., surface or deeper roots, distance from base, growth stages). This study would identify more suitable phenotyping methods for root thickness traits and clearer effects of Sta1 on grain yield.