Genotypic variation in response to aerobic conditions of rice (oryza sativa l )

Genotypic Variation in Response to Aerobic Conditions of Rice (Oryza sativa L.) Nguyen Thi Ai Nghia 2015 Genotypic Variation in Response to Aerobic Conditions of Rice (Oryza sativa L.) A dissertation submitted in partial fulfillment of the requirement for the degree of Doctor of Philosophy by Nguyen Thi Ai Nghia Agricultural Ecology Graduate School of Bioresource and Bioenvironment Sciences Kyushu University Japan 2015 TABLES OF CONTENTS i TABLES OF CONTENTS LIST OF ABBREVIATIONS iii ABSTRACT iv CHAPTER I: General introduction CHAPTER II: Genotypic variation in morphological, physiological and agronomical characteristics of rice under flooded and aerobic conditions Section 1: Genotypic variation in morphological and physiological characteristics of rice under flooded and aerobic conditions Introduction 11 Materials and methods 14 Results 19 Discussion 26 Section 2: Genotypic variation in yield and yield components of rice under flooded and aerobic conditions Introduction 41 Materials and methods 42 Results 43 i Discussion 47 CHAPTER III: Mapping QTLs for root traits under aerobic condition of doubled haploid (DH) population derived from a cross between Koshihikari and Sensho Introduction 55 Materials and methods 57 Results 59 Discussion 64 CHAPTER IV: Aquaporin expressions of rice roots under flooded and aerobic conditions Introduction 84 Materials and methods 87 Results 88 Discussion 90 98 CHAPTER V: General discussion ACKNOWLEDGEMENTS 103 REFERENCES 105 ii LIST OF ABBREVIATIONS DAS: Days after sowing FRL: Fine root length FTRR: Fine to thick root ratio gs: Stomatal conductance L0: Hydraulic conductance LWP: Leaf water potential PH: Plant height RSR: Root to shoot ratio RD: Root diameter RDW: root dry weight RL: Root length RSA: Root surface area RV: Root volume SDW: Shoot dry weight SMC: Soil moisture content TN: Tiller number TRL: Thick root length TDW: Total dry weight WU: Water uptake WUE: Water use efficiency iii ABSTRACT Chapter II Genotypic Variation in Morphological, Physiological and Agronomical Characteristics of Rice under Flooded and Aerobic Conditions Aerobic rice system is a new promising water-saving cultivation technique; however, rice sensitivity to aerobic conditions limits its use We investigated morphological, physiological and agronomical responses of two upland rice genotypes (Beodien and Sensho) and two lowland rice genotypes (KD18 and Koshihikari) to flooded condition (control) and three aerobic conditions (32%, 22%, and 14% soil moisture content (SMC), w/w) in 2013 and to flooded condition and aerobic condition (32% SMC) in 2014 Under aerobic conditions, shoot growth was limited because of a reduction in water uptake Water uptake capacity was highly controlled by root traits such as root dry weight and root length Under aerobic conditions, leaf water potential, stomatal conductance, and root hydraulic conductance declined We found that 32% SMC condition was the most favorable aerobic condition whereas 22% and 14% SMC conditions strongly suppressed rice growth In both years, cultivar Sensho adapted to 32% SMC condition, whereas Koshihikari was not suitable for aerobic rice system, probably because of its limited root growth and lower root plasticity As a consequence, Sensho archived higher shoot biomass and therefore yield than Koshihikari under 32% SMC condition Our iv results also confirm that root traits are important for improving rice performance under aerobic rice system Chapter III Mapping QTLs for Root Traits under Aerobic Condition of Doubled Haploid (DH) Population derived from a Cross between Koshihikari and Sensho A double haploid population from a cross between two japonica genotypes, Koshihikari and Sensho, were used to identify the genetic background of root traits under two water regimes: flooded and aerobic condition (32% SMC (w/w)) Total 26 quantitative trait loci (QTLs) were detected on chromosomes 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11, which explained 12.3– 24.8% of total phenotypic variation The consistency of some QTLs across mapping populations and some QTLs that co-localized with some major QTLs found in this study should be good candidates for marker-assisted selection (MAS) in breeding program Especially, two QTLs for relative RSR on chromosome would be the important QTLs for further studies Moreover, the significant correlations between root traits such as RDW, RL, RSA and RV with WU, SDW and TDW indicated that these root traits may play an important role in water uptake ability and plant growth especially under aerobic condition v Chapter IV Aquaporin Expressions of Rice Roots under Flooded and Aerobic Conditions Aquaporin play a crucial role in plant water uptake and transport To understand the root aquaporin expression and their correlation with root hydraulic conductance, plasma membrane instrinsic proteins (PIPs) and four tonoplast intrinsic protein (TIPs) were studied in upland rice “Sensho” and lowland rice “Koshihikari” under flooded and aerobic conditions (32% SMC (w/w)) Four-week rice seedlings were used for analysis of root hydraulic conductance (L0) and root aquaporin expressions As a result, root L0 was higher in Sensho than Koshihikari under all conditions OsPIP1;3 showed most abundant under flooded condition While the transcript levels of OsPIP2;1, OsTIP1;1 were up-regulated under aerobic condition in both rice genotypes Especially, OsPIP2;1 was up-regulated more than 10-fold in Sensho under aerobic condition and it was about two times higher than that of Koshihikari Other genes, such as OsPIP1;3, OsPIP2;2, OsPIP2;5, OsTIP1;2, OsTIP2;1 and OsTIP2;2 were down-regulated in both rice genotypes under aerobic condition We concluded that OsPIP1;3, OsPIP2;1 and OsTIP1;1 may play an important role on root water uptake; additionally, up and down-regulated of PIP and TIP genes may be linked with root L0 of rice under aerobic conditions vi CHAPTER I GENERAL INTRODUCTION Food demand is increasing with rapidly growing world population The global population is grown from 6.2 billion people in 2002 to 8.2 billion people in 2050 (Rockstrom 2003) It is estimated that, by the year 2025, 60% more rice than currently rice production is necessary to produce to meet the food demand of growing world population (Zhang et al 2009) Rice is the most major staple food in Asia, where it provides 45%–70% of total calorie intake for nearly half of world population (IRRI 2013) Rice is grown in wide range of climate Rice is cultivated in 125 million over the world, account for 9% of world land cultivated area where 57% is irrigated; 32% is rainfed lowland; 9% is upland and 2% is deepwater (IRRI 2013) Among these, irrigated rice provides 75% rice supply thus Asia’ present and future food security depends largely on the irrigated rice production system (Bounman 2001) However, nowadays, the global “water crisis” threatens the sustainability of irrigated rice (Bounman 2001) Water shortage for agricultural irrigation worldwide due to competition from urban and industrial development, degraded irrigation infrastructure, water pollution and climate change (Postel 1998; Hanjra and Qureshi 2010) In Asia, irrigated agriculture accounts for 90% of total diverted freshwater and more than 50% of this is used to irrigated rice (Bounman 2001) Thus irrigated rice is the main consumption of water irrigation Generally, decreasing water availability for agriculture threatens the productivity of the irrigated ecosystem, and ways must be sought to increase grain yield and water use efficiency of rice (Guerra 1998; Belder et al 2004; Yang et al 2007) Vietnam is the Southeast Asia country where rice is major staple food and grown in all regions Total land area for rice production in Vietnam is about 4.2 million (Denning and Vo 1994) In two decades 1980s and 1990s, Vietnam has shifted from a chronic food deficit to become the second world largest rice exporter (Tran and Kajisa 2006) Vietnam divides into seven-major rice- growing regions which are North Mountain Highlands (NMH), Red River Delta (RRD), North Central Coast (NCC), South Central Coast (SCC), Central Highlands (CH), North East South (NES) and Mekong River Delta (MRD) (Fig 1-1) Among these, RRD and MRD are irrigated and intensive rice ecosystems where rice is cultivated 2-3 seasons per year with various cropping pattern RRD and MRD occupy 61% of total rice area and contribute about 65% of rice output In contrast, NCC and SCC are considered as less favorable regions, occupying 19% of total rice area and contributing about 17% of output The remaining rice produced in Vietnam is rainfed lowland or upland rice in the mountainous and highland areas such as NMH and CH which have significant geographical difficulty in increasing irrigated area, being considered as least suitable for rice cultivation (Young et al 2002; 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area (RSA), (C) root volume (RV), (D) root diameter (RD), (E) fine root length (FRL), (F) thick root length (TRL) and (G) fine to thick root ratio (FTRR) under flooded... al 201 4) Rice is vulnerable to even a small loss of available water (Nguyen et al 200 9) Under aerobic conditions, stomata close and transpiration declines even when the soil moisture potential