Abdoulaye Diallo

Two in one sweep: aluminum tolerance and grain yield in P-limited soils are associated to the same genomic region in West African Sorghum

BackgroundSorghum (Sorghum bicolor L. Moench) productivity is severely impeded by low phosphorus (P) and aluminum (Al) toxic soils in sub-Saharan Africa and especially West Africa (WA). Improving productivity of this staple crop under these harsh conditions is crucial to improve food security and farmer’s incomes in WA.ResultsThis is the first study to examine the genetics underlying sorghum adaptation to phosphorus limitation in a wide range of WA growing conditions. A set of 187 diverse sorghum genotypes were grown in 29 –P and + P field experiments from 2006-2012 in three WA countries. Sorghum grain yield performance under –P and + P conditions was highly correlated (r = 0.85***). Significant genotype-by-phosphorus interaction was detected but with small magnitude compared to the genotype variance component. We observed high genetic diversity within our panel, with rapid linkage disequilibrium decay, confirming recent sequence based studies in sorghum. Using genome wide association mapping based on 220 934 SNPs we identified one genomic region on chromosome 3 that was highly associated to grain yield production. A major Al-tolerance gene in sorghum, SbMATE, was collocated in this region and SbMATE specific SNPs showed very high associations to grain yield production, especially under –P conditions, explaining up to 16% of the genotypic variance.ConclusionThe results suggest that SbMATE has a possible pleiotropic role in providing tolerance to two of the most serious abiotic stresses for sorghum in WA, Al toxicity and P deficiency. The identified SNPs can help accelerate breeding for increased sorghum productivity under unfavorable soil conditions and contribute to assuring food security in WA.

Variability in host plant resistance of Sorghum to Striga Hermonthica infestation in West Africa

Fourteen elite sorghum lines were evaluated for their resistance to Striga hermonthica at three locations in Nigeria and Mali. Results showed that many of the lines especially MALISOR 84-1, SAMSORG 41, 97-SB-F5DT-64 (Keninkédié) and the check SRN 39 remained resistant to Striga in all locations with low emerged Striga counts, while SAMSORG 14 had the highest Striga infestation in all locations. Considerable variation in reaction to Striga infestation was observed on Séguètana, 97-SB-F5DT-63 (Wasa), 97-SB-F5DT-65, CMDT 38, CMDT 39 and CMDT 45 which were susceptible to Striga at Samaru, Nigeria but were resistant to Striga at both locations in Mali. Based on low Striga resistance and high grain yield, lines MALISOR 84-1, SAMSORG 41, 97-SB-F5DT-64, 97-SB-F5DT-65, CMDT 39 and SAMSORT 14 have been nominated for wider evaluation across more West African countries.

Study of the Root System of Local and Improved Sorghum Cultivars Grown in Mali

Roots play a fundamental role in plant growth by supplying water and mineral to the stem and leaves. These underground organs are much less known than the aerial organs mainly due to the difficult access to the root systems in soil. In spite of this, only a few studies were conducted on roots. Given the importance of roots for plant growth, a better understanding of their functioning may help solve some issues such as water stress that can affect the performance of the crops. A total of 100 sorghum cultivars collected in the Sahelian zone of Mali an area receiving an annual rainfall of 200 to 600 mm, were used in a root characterization study. The plant materials were composed of 4 races and 5 intermediates sorghum races. Seeds of the entries were planted directly in PVC tubes of 1m containing soil and arranged in completely randomized design with three replications; in one planting date. Each tube was planted in a dugout ground to 50 cm deep. The tubes were distant of 0.50 m within each row and 0.75 m between rows. The trial was watered from the tap every two days until harvest. The results showed high variability among the varieties studied for root length and root density, with a root length reaching over 1.00m. The study did not identify any pattern in the root systems of the four races and their five intermediates races. However, there was a positive correlation between root length and density indicating an increase in root length correspond to an increased root density. The diversity found in the root system could be a basis for improving root architecture in breeding populations and the evaluation of the behaviour of the sorghum varieties with different root systems in water stress conditions.