Abstract
Sorghum is a major staple food crop for the people in semi-arid areas of Africa and Asia. Post-flowering drought is a global constraint of sorghum production. The study aimed to improve stay-green (STG) characteristics of farmer-preferred sorghum varieties in Tanzania using marker-assisted backcrossing. A total of 752 individuals representing five BC2F1 populations and their parents were genotyped using previously reported KASP markers linked with STG 3A and STG 3B quantitative trait loci (QTL). In the BC2F1 populations, the maximum number of individuals with heterozygous alleles were observed in S35*Pato background (37) whereas only seven individuals derived from the B35*Wahi parents’ background contained heterozygous alleles. Of the 30 single nucleotide polymorphism (SNP) markers, favourable alleles were observed at 18 loci in BC2F1 populations. In the BC2F1 generation, the highest (0.127 kg/panicle) grain yield was observed in the B35*NACO Mtama 1 background population. The genotypic analysis revealed the presence of favourable alleles in homozygous conditions at markers loci associated with STG 3A and STG 3B QTLs in BC2F3 populations, suggesting successful introgression of STG QTLs from the donor parents to the recurrent parents. Across water irrigation regimes, the highest (0.068 kg/panicle) mean grain weight was observed in the genotype NA316C. Therefore, our study demonstrated the utility of marker-assisted backcrossing for drought tolerance improvement of locally adapted sorghum varieties in Africa.
Highlights
Drought is a major environmental threat to agriculture sustainability in the world which affects physiological plant growth and performance [1,2]
Five percent of the best-performing genotypes of the BC2F1 populations for the traits plant height, STG, total number of green leaves at maturity, panicle length, panicle width and panicle weight that were screened under field conditions showed significance differences of performance in all traits evaluated across replication
The genotyping information is crucial for exploiting traits from the parents to improve new lines, as STG is a complex trait associated with several genes
Summary
Drought is a major environmental threat to agriculture sustainability in the world which affects physiological plant growth and performance [1,2]. Drought affects water and nutrients uptake from soil and their distribution to plant parts leading to leaf rolling, leaf senescence and lower vegetative plant growth [4]. The common traits indicative of drought tolerance include leaf rolling, leaf senescence, chlorophyll content, days to flowering as well as maturity and root biomass [8]. The exploitation of drought tolerance traits in sorghum had been achieved by mapping STG quantitative trait loci (QTLs) associated with the expression of phenotypic traits such as delay of leaf senescence and maintaining of green leaves at maturity [12]. The genotype B35 sorghum line is characterised by high chlorophyll content, STG and stable root system traits that enable plants to grow and survive better under limited moisture conditions [17]. We aimed to introgress both STG 3A and STG 3B QTLs previously described [17,26] from donor parents B35 and S35 to the most important Tanzanian sorghum varieties NACO Mtama 1, Seguifa, Tegemeo, Macia, Pato, Wagita, Wahi, Hakika and Kenya through MABC for diversifying drought tolerance of sorghum varieties
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