Abstract
Waterlogging is a serious environmental problem that limits agricultural production in low-lying rainfed areas around the world. The major constraint that plants face in a waterlogging situation is the reduced oxygen availability. Accordingly, all previous efforts of plant breeders focused on traits providing adequate supply of oxygen to roots under waterlogging conditions, such as enhanced aerenchyma formation or reduced radial oxygen loss. However, reduced oxygen concentration in waterlogged soils also leads to oxygen deficiency in plant tissues, resulting in an excessive accumulation of reactive oxygen species (ROS) in plants. To the best of our knowledge, this trait has never been targeted in breeding programs and thus represents an untapped resource for improving plant performance in waterlogged soils. To identify the quantitative trait loci (QTL) for ROS tolerance in barley, 187 double haploid (DH) lines from a cross between TX9425 and Naso Nijo were screened for superoxide anion (O2•−) and hydrogen peroxide (H2O2)—two major ROS species accumulated under hypoxia stress. We show that quantifying ROS content after 48 h hypoxia could be a fast and reliable approach for the selection of waterlogging tolerant barley genotypes. The same QTL on chromosome 2H was identified for both O2•− (QSO.TxNn.2H) and H2O2 (QHP.TxNn.2H) contents. This QTL was located at the same position as the QTL for the overall waterlogging and salt tolerance reported in previous studies, explaining 23% and 24% of the phenotypic variation for O2•− and H2O2 contents, respectively. The analysis showed a causal association between ROS production and both waterlogging and salt stress tolerance. Waterlogging and salinity are two major abiotic factors affecting crop production around the globe and frequently occur together. The markers associated with this QTL could potentially be used in future breeding programs to improve waterlogging and salinity tolerance.
Highlights
Waterlogging is a worldwide constraint that considerably affects growth, development, and the distribution of plant species
Waterlogging stress is one of the major abiotic factors limiting agricultural production around the gWloabtee.rloHggeinncge,stirnetsrsoidsuocninegofwthaetemrloagjogrinagbiototilcerfaanctcoersinlimfiietlidngcarogpriscuisltucrraulcpiarlodfourctsiounstaairnoaubnlde tfhooedglporboed. uHcetinocne., iWntartoedrluocgignigngwatotelerrloagngceinigs taolceormanpcleexintrfaieitldancdrocpasnisbecreuacsiiallyfaofrfescutsetdaibnyabvlearfiooouds penrovdiruocntmioenn. tWal afatecrtloorgsgiinncglutdoilnegrasnociel pisroapecrotimesp, ltehxe terxatietnatnodf sctarenssb, edueraastiiloynaofffescttreedss,byanvdapriloaunst environmental factors including soil properties, the extent of stress, duration of stress, and plant development stage when waterlogging occurs [47,48]. Due to these confounding factors and low defefivceileonpcmy eonftadstoapgteedwdhiernecwt saetleerclotigogninmgetohcocudrss, v[4a7ri,o48u]s. iDnduieretcot tchrietseericaohnafvouenbdeienngufsaecdtotros saenledctlofowr wefafitceirelnocgygionfgatdooleprtaendcediirnecptlasneltesc. tion methods, various indirect criteria have been used to select for waterMloagngyinQgTtoLlehraanvceebineepnlaindtesn. tified for waterlogging tolerance based on different agronomic, physiMolaongyicaQl,TaLndhaanvaetobmeiecnal itdraeintsti.fIiendbafrolrey,wQaTteLrlaongagliynsgis tfoolrewraantceerlobgagseindg otonlerdainffceerewnat sapgerrofnoormmeicd, pbahsyesdioloongicpalla,natndheaingahttom[4i9c]a,lgtrraaiitns. yIniebldar[le3y6,],QpTlLanatnsaulyrsvisivfaolr [w50a]t,erlleoagfgcinhglotroolesirsan[c2e7,w37a]s, paenrdfoprmlaendt bbaiosmedasosn[5p1la]nutnhdeeirgwhta[t4e9r]l,oggrgaiinngysiterledss[.3T6]h,epsleanQtTsLurwveivrealid[5e0n]t,ilfieeadf cohnloarlol ssiesv[e2n7,c3h7r]o, manodsopmlaenst, bliimomitiansgs their practical use
Most of these studies were based on quantitative traits, which can vary between different environments, e.g., a quantitative trait loci (QTL) detected in one environment could not necessarily be detected in another environment [52,53,54]
Summary
Waterlogging is a worldwide constraint that considerably affects growth, development, and the distribution of plant species. Soil waterlogging gradually leads to hypoxia and with time may even result in a complete absence of oxygen (anoxia), prompting accumulation of carbon dioxide in the root zone [5] Under these hypoxic and anoxic conditions, oxygen deficiency limits the ability of plant roots to supply water and nutrients to shoots [6,7] and leads to disrupted plant metabolism, reduced growth rates, and lower plant yield. To address the challenge of feeding more than 9.6 billion people by 2050, food production should increase by 70% [8,9] This implies a need to improve the ability of plants to better cope with diverse abiotic factors including salinity and waterlogging
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