Silvestro Meseka

Genetic Gains in Grain Yield of a Maize Population Improved through Marker Assisted Recurrent Selection under Stress and Non-stress Conditions in West Africa

Marker-assisted recurrent selection (MARS) is a breeding method used to accumulate favorable alleles that for example confer tolerance to drought in inbred lines from several genomic regions within a single population. A bi-parental cross formed from two parents that combine resistance to Striga hermonthica with drought tolerance, which was improved through MARS, was used to assess changes in the frequency of favorable alleles and its impact on inbred line improvement. A total of 200 testcrosses of randomly selected S1 lines derived from the original (C0) and advanced selection cycles of this bi-parental population, were evaluated under drought stress (DS) and well-watered (WW) conditions at Ikenne and under artificial Striga infestation at Abuja and Mokwa in Nigeria in 2014 and 2015. Also, 60 randomly selected S1 lines each derived from the four cycles (C0, C1, C2, C3) were genotyped with 233 SNP markers using KASP assay. The results showed that the frequency of favorable alleles increased with MARS in the bi-parental population with none of the markers showing fixation. The gain in grain yield was not significant under DS condition due to the combined effect of DS and armyworm infestation in 2015. Because the parents used for developing the bi-parental cross combined tolerance to drought with resistance to Striga, improvement in grain yield under DS did not result in undesirable changes in resistance to the parasite in the bi-parental maize population improved through MARS. MARS increased the mean number of combinations of favorable alleles in S1 lines from 114 in C0 to 124 in C3. The level of heterozygosity decreased by 15%, while homozygosity increased by 13% due to the loss of some genotypes in the population. This study demonstrated the effectiveness of MARS in increasing the frequency of favorable alleles for tolerance to drought without disrupting the level of resistance to Striga in a bi-parental population targeted as a source of improved maize inbred lines.

Introgression of Alleles from Maize Landraces to Improve Drought Tolerance in an Adapted Germplasm

Maize (Zea mays L.) landraces in the northern Guinea savanna and Sudan savanna in West and Central Africa appear to have some drought-adaptive traits. This study was initiated to assess the level of improvement in yield potential and other agronomic traits achieved under drought stress (DS) and in multiple locations (ML) after introgression of alleles from maize landraces into an elite maize variety (AK9443-DMRSR) via backcrossing. Six backcross (BC) populations together with recurrent parent (AK9443-DMRSR), a commercial hybrid (Oba Super-II), and an improved variety (TZLCOMP4C1) were evaluated under controlled DS and full irrigation (FI) during the dry seasons of 1999 and 2000, as well as in seven ML trials. No significant differences were observed among genotypes for grain yield and most of the traits measured under DS and FI. Significant differences were recorded among genotypes for grain yield and other agronomic traits measured in ML and across 11 environments. Drought stress reduced grain yields of the BC1F2 populations by 64% and recurrent parent by 71%. In ML trials, at least half of the populations were better than recurrent parent. The top three BC1F2 populations produced more grains than the recurrent parent (258–360 kg/ha) and Oba Super-II (555–657 kg/ha) with introgression of only 25% genome of the landraces. We concluded that backcross procedure was able to transfer a quantitative trait of grain yield of an elite recurrent parent into maize landraces. Additional backcross generations are needed for improved performance of the BC1F2 populations in drought-prone environments.

Genetic Analysis of Performance of Maize Inbred Lines Under Drought Stress

The majority of farmers in sub-Saharan Africa (SSA) depend on maize (Zea mays L.), which is mostly grown in drought-prone areas. Understanding the inheritance of drought tolerance would help in developing drought-tolerant maize hybrids that would help increase maize production under erratic rainfalls. Twenty-four maize inbred lines were subjected to NC design II to generate 96 single-cross hybrids. The 24 inbred lines and their 96 hybrids were evaluated under managed drought-stress conditions between 2002 and 2005 at Ikenne, Nigeria. The objectives of this study were to determine the effects of drought-susceptible and drought-tolerant inbred lines on performance of their hybrids, investigate mode of inheritance of drought tolerance, and determine the relationship between parental lines and their hybrids. Most crosses with at least one drought-tolerant parent produced tolerant hybrids, and the crosses between susceptible inbred lines produced susceptible hybrids. General combining ability (GCA) accounted for 55% to 87% of total variation among hybrids for most of the traits. Additive genetic effects influenced grain yield under drought stress. Correlation coefficient between grain yield of the inbred lines and their hybrids was positive and highly significant (r = 0.46***) under severe drought stress and relatively low (r = 0.30**) under mild drought stress and well-watered (r = 0.34**) regimes. Grain yield of inbred lines represented >20% of hybrid yield under severe stress. KU1409, 1824, 9006, 9432, and TZMI501xKU1414x501 had positive GCA effects for yield under drought stress and could be used for developing drought-tolerant hybrids.

Genetic Stability of Grain Yield and Principal Component an analysis in Pearl Millet (Pennisetum glaucum L)

An experiment was conducted to study Principal Component A analysis, yield potential and yield stability of thirty four pearl millet genotypes at Gezira Research Farm (GRF) and Rahad Research Farm (RRS) in the autumn of 2009. The genotypes were of different genetic backgrounds and origin. The experiment was arranged in randomized complete block design with three replications and was carried out during the rainy season. Data were collected on days to 50% flowering, plant height, panicle length, number of productive tillers, head weight, grain yield and 100 seed weight (TSW).Days to50% flowering, head weight, panicle length, number of productive tillers and TSW were significantly and positively associated with grain yield. The first three components of principal component analysis (PCA) accounted for 69% of the total variability attributable to grain yield. The PC scores were associated with days to 50% flowering, panicle length, head weight, number of productive tillers and TSW. Results from yield stability analysis showed that Baladi white was the most stable genotype in terms of grain yield followed by Dembi yellow and Ugandi across sites, while ICMV 155 was the most unstable genotype. At least three of the thirty four pearl millet genotypes, Baladi white, dembi yellow and Ugandi, were stable across the tow site. The three genotypes had grain yield and TSW slightly higher the overall means and could be used in breeding program to further exploit yield potential and stability

Measurement of Pesticide Residues from Chemical Control of the Invasive Spodoptera frugiperda (Lepidoptera: Noctuidae) in a Maize Experimental Field in Mokwa, Nigeria

The management of the fall armyworm Spodoptera frugiperda in maize field necessitates the use a big quantities of insecticides and sometimes the use of multiple types and formulations of chemicals. The use of insecticides in crops is associated with environmental risks and health hazards to both producers and consumers. This study was designed to evaluate the residue of 11 insecticides that were used to control high population of the fall armyworm in maize field in Mokwa, Nigeria. Maize and soil samples were collected from an experimental field to investigate the residue level using high performance liquid chromatography (HPLC, Agilent Technologies, Santa Clara, CA, USA) analysis techniques. Results revealed the presence of five insecticide compounds (Cypermethrin, Deltamethrin, Lambda-Cyhalothrin, Permethrin, and Chorpyrifos) in soil samples with possible adverse effects on soil born organisms and other non-targeted species. In contrast, no residue was found in maize stems and seeds. From these results, we conclude that the treated maize remains safe for consumption and the producers may not get any serious risk of contamination from the chemical control of the fall armyworm.