Crop and Horticultural Sciences

GENETIC VARIABILITY AND ASSOCIATION MAPPING FOR YIELD AND YIELD-RELATED TRAITS IN AFRICAN YAM BEAN [Sphenostylis stenocarpa (Hochst ex. A. Rich) Harms]

2023-07-01T00:00:00Z

GENETIC VARIABILITY AND ASSOCIATION MAPPING FOR YIELD AND YIELD-RELATED TRAITS IN AFRICAN YAM BEAN [Sphenostylis stenocarpa (Hochst ex. A. Rich) Harms] OLOMITUTU, Oluwaseyi Emmanuel African Yam Bean (AYB) is an underutilised legume producing tubers and seeds rich in dietary proteins and minerals, but its Seed Yield (SY) is low. Landraces of AYB are repositories for potential beneficial alleles for the development of varieties with enhanced yield and qualities. However, limited information is available on the extent of genetic variation within available AYB landraces, the genetic basis of the variations and relative importance of SY-related traits, which are required for the development of varieties with improved SY and agronomic characteristics. Hence, genetic variability among some AYB accessions for SY and association of genomic regions with the yieldrelated traits were assessed. One hundred and ninety-six AYB accessions were evaluated for two years at Ibadan, Kano and Ubiaja following standard practices. The experimental design was 14×14 lattice with three replicates. Data were collected on Days to Pod Maturity (DPM), Pod Weight (PDW), Pod Length (PL), Seed Length (SL), Shelling Percentage (SP), 100- Seed Weight (HSW), Seeds Per Pod (SPP) and Seed Thickness (ST), while SY was estimated. Data were subjected to principal component analysis, cluster analysis, correlation analysis, path coefficient analysis, descriptive statistics and ANOVA at α0.05. Estimates of variance components, Genotypic Coefficient of Variation (GCV), Phenotypic Coefficient of Variation (PCV) and broad-sense heritability were computed for the traits. Yield stability index was used to identify superior and stable accessions. The 196 accessions were genotyped using 5,416 DArTseq-based Single Nucleotide Polymorphism (SNP) markers, from which 2,491 markers and 195 accessions were retained after quality filtering. Marker-trait associations were determined using the mixed linear model. Accessions, environments and accession×environment interaction effects were significant for all the traits. The DPM ranged from 118.5±14.3 (TSs-8, Ubiaja) to 220.0±6.0 (TSs-59, Kano), PW ranged from 4.2±0.3 g/plant (138A, Kano) to122.7±17.6 (TSs-421, Ibadan), while PL was shortest in accession TSs-22B (12.0±1.3 cm, Kano) and longest in TSs-51 (27.3±0.6 cm, Ibadan). The SY ranged from 1.3±0.1 (TSs-326, Kano) to 77.6±10.4 g/plant (TSs-421, Ibadan). Variances due to environment and accession×environment interaction were higher than the genotypic variance for all the traits. Also, estimates of PCV were higher than GCV for all traits. Broad-sense heritability ranged from 17.1±3.5% (DPM) to 66.4±0.2% (SL). The first three principal components accounted for 59.7% of the total variation among the accessions. Five major clusters were delineated based on phenotypic characteristics. Shelling percentage (rg=0.76), 100-SW (rg=0.29), DPM (rg=0.45), PW (rg=0.89), SPP (rg=0.20) and ST (rg=0.41) had significant genetic correlations with SY, and exhibited positive direct effects on SY. Accessions TSs- 119, TSs-101, 138A, TSs-4, TSs-157A and TSs-61 were identified as superior and stable. Across locations, 24 SNP markers were significantly associated with the traits at a threshold of –log (p) =4, and explained 7.1 to 12.8% of the phenotypic variation among the accessions. A wide genetic variation exists among the African yam bean accessions. Selection criteria for improved seed yield in African yam bean should include shelling percentage, 100-seed weight, days to pod maturity, pod weight, seeds per pod and seed thickness.

GENETIC ANALYSIS AND DROUGHT STRESS ASSESSMENT OF MARKER-BASED IMPROVED PROVITAMIN-A MAIZE SYNTHETICS

2023-07-01T00:00:00Z

GENETIC ANALYSIS AND DROUGHT STRESS ASSESSMENT OF MARKER-BASED IMPROVED PROVITAMIN-A MAIZE SYNTHETICS ISEGHOHI, Osemare Innocent Maize is an important staple in Sub-Saharan Africa (SSA) but most varieties are low in Provitamin-A (PVA) carotenoids, and the performance adversely affected by drought stress. Development and adoption of PVA carotenoids-enriched drought-tolerant Maize Synthetics (MS) could help improve maize yields and reduce vitamin A deficiency in SSA. Marker Assisted Recurrent Selection (MARS) could be used to improve the nutritional quality and resilience of maize. However, the effects of MARS on carotenoid contents of MS and performance of the PVA carotenoids-enriched MS in hybrid combinations and under drought stress have not been adequately documented. The level of improvement of carotenoid content of MS using MARS, combining ability and effects of drought stress on yield of PVA carotenoids-enriched MS were evaluated. Three selection cycles (C0, C1 and C2) of two MS (PVASYNHGA and PVASYNHGB) each improved through MARS were crossed to generate nine Varietal-cross Hybrids (VH). The genotypes [selection cycles, VH and a check (PVASYN13)] were evaluated at Ikenne, Mokwa, Saminaka and Zaria using a 4×4 lattice design with four replicates. The genotypes were also evaluated under Managed Drought Stress (MDS) at Ikenne following standard procedures. Days to Silking (DS), Plant Height (PH, cm) and Ear Aspect (EA) were measured and Grain Yield (GY, t/ha) was estimated. The α- carotene, β-cryptoxanthin and β-carotene contents (μg/g) of grains were determined using HPLC, and PVA content (μg/g) estimated. Data were analysed using descriptive statistics and ANOVA at α0.05. Genetic gain/cycle, Mid-parent Heterosis (MPH), Specific Combining Ability (SCA), General Combining Ability (GCA) and Drought Tolerance Index (DTI, where DTI of 0–0.49=low, 0.50–0.69=moderate and 0.70– 1.0=high) were estimated. Genotype and location effects were significant for GY, DS, PH, EA and PVA carotenoids, while genotype×location effect was significant for DS, EA, β-carotene and PVA. The GY, DS, PH, EA, α-carotene, β-cryptoxanthin, β-carotene and PVA ranged from 3.7±0.3 (Ikenne) to 6.4±0.4 (Mokwa), 54.4±0.8 (Mokwa) to 63.0±0.8 (Zaria), 206.4±5.9 (Ikenne) to 222.5±8.0 (Saminaka), 2.4±0.2 (Saminaka) to 2.7±0.2 (Ikenne), 0.8±0.1 (Ikenne) to 1.0±0.1 (Mokwa), 2.4±0.3 (Ikenne) to 3.3±0.4 (Mokwa), 5.1±0.3 (Ikenne) to 6.5±0.8 (Mokwa) and 6.8±0.3 (Ikenne) to 8.7±0.8 (Mokwa), respectively. The MARS increased β-carotene and PVA by 25.0% and 15.0%, respectively in PVASYNHGA, and α-carotene by 5.0% in PVASYNHGB. Four VH (PVASYNHGBC0/PVASYNHGAC0, PVASYNHGBC2/PVASYNHGAC0, PVASYNHGBC0/PVASYNHGAC1 and PVASYNHGBC1/PVASYNHGAC2) had significant MPH and SCA for GY. Only PVASYNHGBC0/PVASYNHGAC0 (4.0%), PVASYNHGBC0/PVASYNHGAC2 (2.6%) and PVASYNHGBC0/PVASYNHGAC1 (2.3%) exhibited MPH for PVA. Three genotypes [PVASYNHGAC0 (0.7), PVASYNHGAC1 (0.3) and PVASYNHGBC2 (0.1)] had significant GCA for GY, while PVASYNHGAC2 (1.09) and PVASYNHGBC0 (1.27) had significant GCA for PVA. Under MDS, significant genotypic differences were observed for GY and DTI. Drought stress reduced GY by 31.4% (PVASYNHGBC1/PVASYNHGAC2) to 69.8% (PVASYNHGBC1/PVASYNHGAC0). The four VH with MPH for GY out-yielded the check by 12.7% to 16.4% and exhibited moderate to high DTI. Marker-assisted recurrent selection improved carotenoid contents of PVASYNHGA than PVASYNHGB. Genotypes PVASYNHGAC2 and PVASYNHGBC0 are suitable for provitamin-A inbred line development. Drought stress reduced grain yield of theviii maize synthetics but four varietal-cross hybrids (PVASYNHGBC0/PVASYNHGAC0, PVASYNHGBC2/PVASYNHGAC0, PVASYNHGBC0/PVASYNHGAC1 and PVASYNHGBC1/PVASYNHGAC2) were drought tolerant.

YIELD OF CASSAVA (Manihot esculenta Crantz) VARIETIES AS INFLUENCED BY NPK APPLICATION AND STEM PROPERTIES IN TWO AGRO-ECOLOGIES OF NIGERIA

2023-04-01T00:00:00Z

YIELD OF CASSAVA (Manihot esculenta Crantz) VARIETIES AS INFLUENCED BY NPK APPLICATION AND STEM PROPERTIES IN TWO AGRO-ECOLOGIES OF NIGERIA OKETADE, ELIZABETH IFEOLUWA Cassava is a major staple and commercial crop in the tropics, its yield is constrained by factors such as decline in soil fertility and use of inappropriate planting materials. Fertiliser application and use of appropriate planting materials could improve yield of suitable cassava varieties. However, there is dearth in knowledge on appropriate fertiliser formulations, application rate and qualities of stem cuttings for improved cassava varieties. Therefore, effects of different fertiliser formulations, application rates and stem portions and lengths of stem cuttings on cassava yield were evaluated in two agroecologies of Nigeria. Experiments were conducted at Ikenne (Rain-Forest), Ibadan and Tsonga (DerivedSavanna). Four cassava varieties: TMEB419-(V1), IBA010040-(V2), IBA011412-(V3) and IBA070593-(V4) were planted and four fertiliser formulations [NPK15:15:15-(F1), TSP+KCl-(F2), urea+KCl-(F3) and urea+TSP-(F4)] were applied, so as to supply 0, 45- (R45) or 75-(R75) kg N, P2O5 and K2O/ha. The experiment was a 4 × 4 × 2 factorial in a Randomised Complete Block Design (RCBD) with three replicates. Controls were no fertiliser-(F0). In another experiment, the four cassava varieties with three stem portions: Basal-(S1), Middle-(S2) and Top-(S3) and two stem cutting lengths (cm): 15-(L15) and 30-(L30) were laid out as a 4 × 3 × 2 factorial in a RCBD replicated three times. Plants were spaced at 1.0 × 0.8 m and harvested at 12 months after planting. Data estimates on Fresh Storage Root Yield‒FSRY (t/ha), Dry Storage Root Yield‒DSRY (t/ha) and Plantable Stem Yield‒PSY (t/ha) were analysed using descriptive statistics and ANOVAα0.05. Cassava varieties, fertiliser formulations and rates and their interactions were significantly different for all variables. Combination involving V3+F1+R75 resulted in significantly higher FSRY than all others. The FSRY ranged from 9.5±0.6 (V4+F4+R45) to 22.5±0.6 (V3+F1+R75). The DSRY ranged from 2.2±0.1 (V4+F4+R45) to 5.3±0.2 (V2+F2+R75), while PSY ranged from 7.8±0.3 (V1+F4+R75) to 15.4±0.3 (V2+F0). Thevi FSRY for R75 (15.4±0.8) was higher than that of R45 and F0 by 1.1% and 11.9%, respectively. The FSRY was in the order 29.4±0.9-Ikenne ˃24.8±0.6-Ibadan ˃18.5±0.8- Tsonga. The order of FSRY was 22.5±0.6 (V3) ˃19.4±0.4 (V2) ˃12.7±0.3 (V1) ˃12.4±0.6 (V4). Overall, PSY for F0 was the best and increased from 12.5±0.5 (Tsonga) to 18.1±0.4 (Ibadan) to 21.9±0.6 (Ikenne). Across the sites, FSRY ranged from 10.3±2.1 (V4+S3+L15) to 26.4±0.8 (V3+S2+L30). The DSRY ranged from 0.9±0.6 (V4+S3+L15) to 4.7±0.6 (V2+S2+L30) and PSY ranged from 2.5±1.1 (V4+S3+L15) to 9.6±0.3 (V3+S1+L30). The DSRY of L30 was 25.2% higher than L15 (2.4±0.2) and declined from 3.7±0.8 (Ikenne) to 3.3±0.7 (Ibadan) to 1.4±0.3 (Tsonga). The FSRY increased from 9.8±0.6 (S3) to 11.7±0.6 (S2) to 12.1±1.2 (S1). The PSY declined from 16.5±0.6 (Ibadan) to 14.7±0.9 (Ikenne) to 9.5±1.1 (Tsonga). Application of NPK 15:15:15 at 75 kg N, P2O5 and K2O ha-1 to TMEB419 in derived savanna and Urea+KCl at the same rate to IBA011412 in rain forest enhanced yield of cassava. A 30 cm basal stem cutting portion should be adopted for increased storage root production.

WEED MANAGEMENT IN CASSAVA (Manihot esculenta Crantz) WITH SELECTED PRE- AND POST-EMERGENCE HERBICIDES UNDER ALTERNATIVE APPLICATION SEQUENCE

2022-01-01T00:00:00Z

WEED MANAGEMENT IN CASSAVA (Manihot esculenta Crantz) WITH SELECTED PRE- AND POST-EMERGENCE HERBICIDES UNDER ALTERNATIVE APPLICATION SEQUENCE ALABI, Mariam Adenike Cassava is a major crop in Africa, but weed management at its early growth stage is a problem. Pre-emergence Herbicides (PrH), often supplemented with Post-emergence Herbicides (PoH), are used for Weed Management (WM) in cassava. Delayed application of PrH could necessitate the use of PoH before PrH. There is a dearth of information on the effects of application of PoH before PrH as a WM strategy in cassava. Therefore, this study was conducted to evaluate some PrH and PoH and their alternative application sequences on WM, growth and yield of cassava. Three PrH: sulfentrazone, flumiosaxin+pyroxasulfone and indaziflam+isoxaflutole at 0.6, 0.11+0.14 and 0.068+0.20 kg a.i./ha, respectively and three PoH: clethodim+lactofen (0.21+0.41 kg a.i./ha), trifloysulfuron-sodium (5.25 g a.i./ha) and carfentrazone-ethyl (5.84 g a.i./ha) were evaluated in cassava (TMEB419) plots planted at 1x0.8 m2. The PrH were evaluated in plots laid in a Randomised Complete Block Design (RCBD). Plots treated with atrazine+S-metolachlor (0.73+1.30 kg a.i./ha) plus 2-Hoe-Weeding (ASm+2HW), weed-free and a weedy-check served as controls. Cassava Plant Height (CPH)-cm, stand count and Weed Dry Weight (WDW)-g/m2 per plot were measured at eight Weeks After Planting (WAP). In another experiment, two spray methods (banded and broadcast) of the PoH at two WAP were evaluated on sprouted cassava in a split-plot design. Spray methods and PoH were the main and sub-plots, respectively. Crop injury (%) and Weed Control Efficacy (WCE)-% were assessed. Thereafter, two sequences of application of PrH and PoH (PrH-PoH and PoH-PrH) were evaluated using split-plot arrangements in RCBD. The PrH or banded PoH were either the main or sub-plots in the sequences. Data were collected on WCE and cassava Storage Root Yield-SRY (t/ha). All experiments were replicated three times. Data were analyzed using descriptive statistics and ANOVA at α0.05. The CPH ranged from 38.0±1.2 (sulfentrazone) to 53.2±1.3 (weed-free). Stand count ranged from 10471.3±0.0 (indaziflam+isoxaflutole) to 11976.1±0.0 (weed-free). Significant reduction (%) in WDW relative to the maximum from weedy-check (110 g/m2) was in the order: 76.4 (sulfentrazone) <82.1 (flumioxazin+pyroxasulfone) <87.3 (indaziflam+isoxaflutole) <89.1 (ASm+2HW) <91.8 (weed-free). Broadcast spray caused 55.19 ±10.7% crop injury which was significantly higher than 7.4 ±7.0% in banding. Crop injury of 92.2±10.7% (carfentrazone-ethyl), 54.8±10.7% (trifloysulfuron-sodium) and 19.0±7.1% (clethodim+lactofen) due to broadcastspraying were significantly higher than 6.3±7.0%, 7.8±7.0% and 8.2±7.0%, respectively in bandspraying. The WCE at 79.0±0.6% (carfentrazone-ethyl) was significantly lower than 88.4±0.6% (trifloysulfuron-sodium) and 97.0±0.6% (clethodim+lactofen). The WCE in PrH-PoH was significantly higher than in PoH-PrH. The WCE involving PrH-PoH application was 38.0% (sulfentrazone), 29.4% (flumioxazin+pyroxasulfone), 28.1% (carfentrazone-ethyl) and 22.3% (trifloysulfuron-sodium) significantly higher than those of their PoH-PrH. However, those of indaziflam+isoxaflutole (7.0%) and clethodim+lactofen (6.3%) were not significantly different. The SRY of 14.0±1.9 (sulfentrazone) was significantly lower than 28.7±1.9 (flumioxazin+pyroxasulfone) and 31.5±2.0 (indaziflam+isoxaflutole) across the PoH, while 22.7±1.9 (carfentrazone-ethyl), 23.9±1.9 (trifloysulfuron-sodium) and 26.7±1.9 (clethodim+lactofen) across the PrH were comparable. Indaziflam+isoxaflutole and flumiosaxin+pyroxasulfone, and banded spray of trifloysulfuronsodium and clethodim+lactofen enhanced cassava growth and weed control efficacy. Sequences involving clethodim+lactofen before or after indaziflam+isoxaflutole improved weed control efficacy and yield of cassava.