Andekelile Mwamahonje

Maize is the most staple food crop produced in sub-Saharan Africa which its cultivation has been expanding with time however, the productivity remains low. Low productivity of maize in Africa is contributed by different challenges such as pests and diseases, drought, floodings which are associated with the effects of climate change. Drought is among the critical constraints in maize production causing yield loss up to 100% under extreme conditions. With these challenges researchers have come with some of the promising technologies that help to reduce the effect of climate changes for instance breeding new climate resilience maize varieties which using modern breeding tools like marker assisted backcrossing, quantitative trait loci, genomewide association studies, double haploid, gene editing, genomic selection and high throughput phenotyping. These tools map traits of target for introgression to recipient varieties thus reducing time of breeding cycles. Some of the climate of improvement for climate resilience include drought and heat tolerance, high stay green with low less leaf rolling, stemborer and fall armyworm tolerance, water-use efficiency and high grain yield. Effort have been done by CIMMYT in collaboration with National Agricultural Research Institutes have developed climate resilient crop varieties, however, with pace of climate change there is more effort to diversify varieties for sustainable climate resilience that will strengthen food security in sub-Saharan Africa which is the most vulnerable to climate change. There is a need to integrate approaches to cope with climate change such as use of next-generation genomic technologies, digital agriculture and data-driven approaches, strengthening seed systems, integration of farmer preferences and socioeconomic factors into the breeding process, and adaptive breeding programs based on climate scenarios. These will shorten breeding cycles and come up with new technologies that cope with variation of climate at certain intervals.

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.

Sorghum (Sorghum bicolor [L.] Moench) is an important food crop for people in semi-arid Africa. The crop is affected by post-flowering drought; therefore, the study was conducted to screen traits contributing to drought tolerance using BC₂F₄ sorghum genotypes in stressed and unstressed water conditions in a split-plot design. Water stress (0 mm/day) was applied at post-flowering to plant maturity in water-stressed treatment. The genotype SE438 produced the highest grain yield (2.65 ton ha⁻¹) in water-stressed environment and NA316C yielded highest (3.42 ton ha⁻¹) under well-watered (7 mm/day) environment. There were significant differences of most traits evaluated at p < 0.01 across environments. The mean squares of traits for genotypes by environments revealed interactions at p < 0.05 and p < 0.01. The indices geometric mean productivity (GMP) and mean productivity (MP) were highly correlated with yield under well-watered (YP) and water-stressed condition (YS) and each other. The first principal axis (PC1) explained 59.1% of the total variation. It is the best indicator of yield potential and drought tolerance of sorghum genotypes in this study. Therefore, further improvement is needed to strengthen drought tolerance and yield in sorghum.