Biology subjects

Ogwuche, T. O.

Publications and source records attributed to Ogwuche, T. O..

3 recordsLinked to original sources

bioRxiv2026

Breeding cassava for intercropping with cowpea: monoculture selection captures most intercrop selection gain, but targeted testing remains necessary

Intercropping dominates smallholder cassava production in sub-Saharan Africa, yet cassava breeding programs evaluate genotypes exclusively under monoculture. Despite consistently reported system-level yield advantages, cassava yield is reduced by 17 to 51% under intercropping, indicating a need to reduce this competitive disadvantage through breeding. However, the quantitative-genetic foundations of intercrop breeding remain uncharacterized for tropical root crop systems. We hypothesized that monoculture selection would capture most, but not all, genetic merit for intercropping and that a limited tester set would be sufficient if general mixing ability predominated. We evaluated 120 cassava clones previously selected under monoculture in IITA advanced yield trials, testing them under monoculture and in intercrop with two contrasting cowpea varieties across two years at Ibadan, Nigeria. Spatial mixed models quantified genetic variation, genotype by cropping system interaction, cross system genetic relationships, realized selection gain, mixing ability, tester effects, and land equivalent ratio. Intercropping reduced cassava fresh root yield by 19%, but total land equivalent ratios exceeded 1.0 for all clones, confirming a system-level land use advantage. Cassava performance under intercropping was heritable, with estimates of 0.50 to 0.75, and genotype by cropping system interaction was not significant. Genetic correlations between monoculture and intercrop performance were high and approached unity (rg = 0.92 to 0.99), and selection efficiency was 26 to 44% at 10% intensity, confirming that high genetic correlation does not guarantee effective indirect selection. Monoculture selection captured approximately two-thirds of direct intercrop gain. General mixing ability dominated, specific mixing ability was negligible, and producer effects explained 20 to 47% of intercrop variance. The two architecturally and phenologically contrasting cowpea varieties had limited influence on cassava rankings. Here, we show for the first time that cassava breeding for intercropping can retain monoculture selection during early stages while adding two representative cowpea testers at the advanced trial stage. This staged strategy aligns cassava breeding with diversified smallholder systems without creating a separate pipeline.

plant biology↗

bioRxiv2026

Optimizing multi environment cowpea yield trial by appraising the fitness and similarities among test sites: a case study of IITA cowpea breeding program

Optimization of Multi environment trials (MET) trials require an efficient testing network consisting of ideal sites which should be highly discriminative and representative of their mega environments. Also concurrently managing sites that are similar in terms of information there give about genotype performance adds no extra utility to the breeding program. The objective of this study was to appraise the testing network of the cowpea breeding program of the International Institute of tropical Agriculture (IITA) based in Nigeria on the basis of their representativeness and discriminatory ability for grain yield, investigate the similarities among them and assess the variance components. 6 set sets of Advance yield trial with unique entries were analysed using Mixed models, best linear unbiased estimate (BLUPs) and BLUP based GGE biplot. Results showed significant means squares Genotype x Location interaction effect for all 6 sets; this justifies the to study GEI in cowpea, partitioning variance showed that Environment main effect accounted for the largest proportion of the total phenotypic variance, with a range of 58.1 (Adv 4) to 73.9% (Adv 3), Environment was followed by Genotype x Location interaction which explained between 16.1% (Adv 5) to 22.6% (Adv 4). Genotype main effect accounted for the least with a range of 9.5% (Adv 6) to 19.3% (Adv 4). Broad sense-heritability for GY was high in Advance 1-5 (ranging from 0.62-0.70) and medium in advance 6 (0.53). Shika June, Shika August and Minjibir consistently showed high discriminativeness with Minjibir been the most discriminating environment for this study. Ibadan September and Ibadan May on the other hand consistently showed poor discriminating ability while BUK was inconsistent having good discriminative ability in Sets 1 and 3 while it was poor in sets 2, 5 and 6. In terms of representativeness, no environment consistently had desirable results however, Shika August and Shika June were most representative while Minjibir was least representative. On the basis of discriminativeness and representativeness, the six environments were ranked in other of desirability as Shika August> Shika June> Minjibir > Ibadan September > BUK farm > Ibadan May. In terms of similarity among environments, both the BLUP-Based GGE biplot and genotypic correlations indicated that Ibadan May and September were consistently grouped together and highly correlated; indicating that they are similar, while, Shika August and Shika June were found to be unique. Ibadan May was therefore adjudged a redundant location and could be dropped and replaced without any loss of accuracy because it was neither discriminative nor representative in all biplots draw and it consistently fell in the same Mega environment with Ibadan September. We concluded that there is a need to sample more testing sites and validate their fitness for multi environment yield trials using methods applied in this study.

genetics↗

bioRxiv2025

PERFORMANCE OF FOUR NEWLY RELEASED CASSAVA VARIETIES IN A FALLOWED LAND OVER TWO FARMING SEASONS

Cassava (Manihot esculenta Crantz) is an important crop for humans due to its staple and industrial values. Currently the demand is more than the supply as the current output falls below the expected. This necessitated the breeding of superior genotypes that are high yielding. These superior genotypes also requires a fertile soil for optimum production. However, this has been primarily achieved through the application of inorganic manures. It is then important to evaluate four newly released cassava varieties in an organically enriched soil relative to the local best variety. Four newly released cassava varieties, Hope, Obasanjo2, Baba 70, and Game changer, and one Local Best (LB) was planted in 5-years fallowed farm lands at three plots (A, B and C) for 2 seasons. It was a three-way factorial (5-varieties*3-farms*2-seasons) arranged in a randomized complete block design and replicated three times. Data were taken on the Fresh Tuber Weight (FTW) and Stem Height (SH) per variety, and pre and post soil status. Data were analyzed using analysis of variance, while differences in varietal means were separated using least significant differences at 5% level of significance. The FTW and SH differed significantly across varieties, years and interaction between variety, farms and year, and ranged from 19.2{+/-}0.5 (LB) to 41.0{+/-}0.5 (Obasanjo2), 32.1{+/-}0.4 (farm C) to 34.1{+/-}0.4 (farm A), 30.4{+/-}0.3 (year two) to 35.0{+/-}0.3 (year one), and the interactions between variety and year, farms and year, and variety, year and farms were significant. The soil macro and micro elements declined in the post relative to the pre status. The yield obtained from the improved varieties almost doubled the local best and yield declined in the second season.

plant biology↗