Genetic diversity in yield traits and kernel composition of selected Ethiopian sorghum landraces

Abstract

𝑬𝒏𝒈𝒍𝒊𝒔𝒉 Climate-resilient and high-yielding sorghum cultivars must be developed for sustainable food systems and improved livelihoods in sub-Saharan Africa. Low grain protein, Fe and Zn concentrations are a frequent problem in food crops and they affect the crop's nutritional value, particularly in cereals. In this study, a total of 361 Ethiopian sorghum landraces with four commercial checks were grown under well-watered, wet intermediate and natural drought conditions for two consecutive seasons. The purpose of this research was to assess the genetic diversity and drought tolerance of this Ethiopian sorghum landrace collection using agronomic and grain quality traits and to select promising lines for production and/or breeding. The specific objectives were to (i) assess the level and pattern of genetic variation and drought adaptation in a sorghum landrace collection using phenotypic traits, (ii) evaluate chemical composition, genotype by environment interaction, drought effects and environmental influence and determine performance and stability of sorghum landraces, (iii) identify genomic regions associated with grain quality to determine the genetic basis for starch, protein and mineral concentrations of Ethiopian sorghum landraces. In stress environments, yield and yield components as well as grain quality traits had low means, range, genetic variance (σ²g) and heritability values.

In terms of grain yield performance under different water regimes, Melkassa (irrigated) had a 54.5% higher mean grain yield than Miesso (drought stress) in 2020 and Melkassa (irrigated) had a 26.9% higher mean grain yield than Miesso (drought stress) in 2021. Therefor drought stress reduced mean grain yield by 44.6% and grain weight by 14%. In all environments, ten genotypes (G189, G210, G125, G324, G325, G353, G319, G219, G187 and G229) had the highest stress tolerance index (STI), geometric mean productivity (GMP), mean productivity (MP) and yield in non-stress conditions (Yp) and stress conditions (Ys). In stress environments, starch content decreased by 5%, while protein content increased by 21% when compared to wet intermediate conditions. The Zn content was 60% and 55% higher in wet intermediate environments than in irrigated and stress environments, respectively. The Fe content was 21% and 13% higher in wet intermediate environments than in irrigated and stress environments, respectively. A genome-wide association study (GWAS) on 365 diverse Ethiopian sorghum landraces identified 209,572 single nucleotide polymorphisms (SNPs) (HB 𝘱 ≤ 0.05). Several candidate genes were identified that were significantly associated with grain Zn, Fe, starch, protein and ash concentrations, such as LEA, CHI, bZIP, ARF12 and WOX6.

The Late Embryogenesis Abundant (LEA) and basic leucine zipper (bZIP) family of proteins are involved in various stress responses in plants. The ABC transporter and sugar carrier proteins, Auxin Response Factors 12 (ARF12), Alpha-glucan phosphorylase and Zinc finger CCHC gene, are known for starch synthesis and storage in growing seeds. The WUSCHEL-related homeobox 6 (WOX6) and TatD family of hydrolases genes, acts as a transcription factor and is known to regulate stem cell maintenance and differentiation. Chitinase (CHI), flavonoid glycosides, architecture1 (tga1) and Class III peroxidase 70 and 69 precursors are all engaged in biological processes including plant defence against pathogens. The Zinc finger proteins (ZNFs) family is involved in Zn and Fe ion uptake and transport. These genes are involved in various biological processes such as stress response, starch synthesis, plant development and defence. The identification of loci associated with grain quality provides new insight into the genetic control of the traits, while sorghum landraces with nutritious grains can serve as sources of genes for breeding for good nutritional value. ___________________________________________________________________

𝑨𝒇𝒓𝒊𝒌𝒂𝒂𝒏𝒔 Klimaatbestande en hoë-opbrengs sorghumkultivars moet ontwikkel word vir volhoubare voedselstelsels en verbeterde lewensbestaan in Afrika suid van die Sahara. Lae graanproteïen-, Fe- en Zn-konsentrasies is ’n gereelde probleem in voedselgewasse en dit beïnvloed die gewas se voedingswaarde, veral in graan. In hierdie studie is ’n totaal van 361 Ethiopiese sorghum landrasse met vier kommersiële ondersoeke gekweek onder goed natgemaakte, nat intermediêre en natuurlike droogtetoestande vir twee opeenvolgende seisoene. Die doel van hierdie navorsing was om die genetiese diversiteit en droogtetoleransie van hierdie Ethiopiese sorghum landrasversameling te bepaal deur gebruik te maak van agronomiese en graankwaliteit eienskappe en om belowende lyne vir produksie en/of plantteling te kies.

Die spesifieke doelstellings was om (i) die vlak en patroon van genetiese variasie en droogte-aanpassing in ’n sorghumlandrasversameling te evalueer deur fenotipiese eienskappe te gebruik, (ii) chemiese samestelling, genotipe volgens omgewingsinteraksie, droogte-effekte en omgewingsinvloed te evalueer en prestasie en stabiliteit van sorghumlandrasse te bepaal, (iii) en genomiese streke te identifiseer wat met graankwaliteit geassosieer word om die genetiese basis vir stysel-, proteïen- en mineraalkonsentrasies van Ethiopiese sorghumlandrasse te bepaal. In stresomgewings het opbrengs- en opbrengskomponente sowel as graankwaliteit-eienskappe lae gemiddeldes, omvang, genetiese variansie (σ²g) en oorerflikheidswaardes gehad. Wat graanopbrengsprestasie onder verskillende waterregimes betref, het Melkassa (besproei) ’n 54,5% hoër gemiddelde graanopbrengs as Miesso (droogtestres) in 2020 gehad en Melkassa (besproei) het ’n 26,9% hoër gemiddelde graanopbrengs as Miesso (droogtestres) in 2021 gehad. Daarom het droogtestres die gemiddelde graanopbrengs met 44,6% en graangewig met 14% verminder. In alle omgewings het tien genotipes (G189, G210, G125, G324, G325, G353, G319, G219, G187 en G229) die hoogste strestoleransie-indeks (STI), geometriese gemiddelde produktiwiteit (GMP), gemiddelde produktiwiteit (MP) en opbrengs in nie-strestoestande (Yp) en strestoestande (Ys) gehad. In stresomgewings het styselinhoud met 5% afgeneem, terwyl proteïeninhoud met 21% toegeneem het in vergelyking met nat intermediêre toestande. Die Zn-inhoud was onderskeidelik 60% en 55% hoër in nat intermediêre omgewings as in besproeiings- en stres-omgewings. Die Fe-inhoud was onderskeidelik 21% en 13% hoër in nat intermediêre omgewings as in besproeiings- en stres-omgewings.

’n Genoomwye assosiasiestudie (GWAS) op 365 diverse Ethiopiese sorghum landrasse het 209 572 enkelnukleotied polimorfismes (SNPs) (HB 𝘱≤ 0,05) geïdentifiseer. Verskeie kandidaatgene is geïdentifiseer wat betekenisvol geassosieer is met graan Zn, Fe, stysel, proteïen en as konsentrasies, soos LEA, CHI, bZIP, ARF12 en WOX6. Die Late Embryogenesis Abundant (LEA) en basiese leucine zipper (bZIP) families van proteïene is betrokke by verskeie stresreaksies in plante. Die ABC-vervoerder en suikerdraerproteïene, Auxin Response Factors 12 (ARF12), Alfa-glukaanfosforilase en Sinkvinger CCHC-geen, is bekend vir styselsintese en berging in groeiende sade. Die WUSCHEL-verwante homeobox 6 (WOX6) en TatD familie van hidrolase gene, dien as ’n transkripsie faktor en is bekend om stamsel-instandhouding en -differensiasie te reguleer. Chitinase (CHI), flavonoïedglikosiede, argitektuur1 (tga1) en Klas III peroksidase 70 en 69 voorlopers is almal betrokke by biologiese prosesse, insluitend plantverdediging teen patogene. Die sinkvingerproteïene-familie (ZNF) is betrokke by Zn- en Fe-ioonopname en -vervoer. Hierdie gene is betrokke by verskeie biologiese prosesse soos stresreaksie, styselsintese, plantontwikkeling en verdediging. Die identifisering van lokusse wat met graankwaliteit geassosieer word, verskaf nuwe insig in die genetiese beheer van die eienskappe, terwyl sorghumlandrasse met voedsame grane as bronne van gene vir plantteling vir goeie voedingswaarde kan dien. ___________________________________________________________________

Abstract in other languages 𝘚𝘤𝘳𝘰𝘭𝘭 𝘥𝘰𝘸𝘯 𝘧𝘰𝘳 𝘈𝘧𝘳𝘪𝘬𝘢𝘢𝘯𝘴, 𝘚𝘦𝘚𝘰𝘵𝘩𝘰 𝘢𝘯𝘥 𝘐𝘴𝘪𝘡𝘶𝘭𝘶