No abstract

The success in identifying heterosis in hybrid maize (Zea mays L.) breeding depends on the availability of reliable genetic diversity among maize inbred lines. Conventional methods of breeding have been boosted by the availability and efficiency of molecular markers. Coupling simple sequence repeat (SSR) markers with morphological markers provides thorough starting information for new inbred lines, especially from different genetic backgrounds. Furthermore, recent evidences that the environment can influence the epigenetic structure of the genome have necessitated morphological screening of crops during breeding programmes. This study used 28 agronomic traits and 14 SSR markers which are distributed uniformly in ten (1-10) inbred lines, namely EM11-133, EM12-210, OSU23i, CML395, CML202, CML442, CML444, CML208, CML312 and CML204 from Kenya, International Centre for the Improvement of Maize and Wheat (CIMMYT), and another (OSU 23i) from USA. The aim was to investigate their morphological and genetic diversity, categorise the inbred lines into useful groups based on the molecular profiles and morphological traits, and lastly determine the level of phenotype-genotype correlation. The dissimilarity calculated using SSR markers had a mean morphological dissimilarity of 0.895403, an r value of -0.1421 and a p -0.9840. The dissimilarity between the molecular and morphological traits was 0.860465. Comparison between the molecular and morphological data had a dissimilarity matrix with an r -0.2323 and a p value of 0.0120. This was probably due to intrinsic synteny in maize genome. The dendrograms generated with hierarchical Unweighted Pair Group Method with Arithmetic mean (UPGMA) cluster analysis of the Jaccard's similarity coefficient matrices revealed four major clusters. The Co-ancestry distance showed six tied groups with the Kenya cluster showing some differentiation with Exact Tests for population differentiation with a p = 0.0513. The American inbred line (OSU 23i) segregated alone, while the Kenya lines (EM11-133 and EM12-210) had close homology with the CIMMYT inbred lines (CMLs). A total of 2.0 alleles were detected among the inbred lines using bulk DNA samples and 14 SSR loci. Clustering analysis based on the genetic similarity coefficients separated the inbred lines into 4 groups with the American inbred line seeming to be genotypically more diverse from the others.Key Words: Genetic diversity, molecular markers, SSR, Zea mays RÉSUMÉLe succès dans l'identification des hétérosis de maïs hybrides (Zea mays L.) dépend de la disponibilité d'une diversité génétique fiable dans les lignées endogames du maïs. Les méthodes conventionnelles de l'hybridation avaient été améliorées par la disponibilité et l'efficacité des marqueurs moléculaires. Le couplage des marqueurs simples de sequence répétée (SSR) avec les marqueurs morphologiques fournit des informations fondamentales précises pour les nouvelles lignées endogames, principalement de différente constitution génétique. En outre, les recentes évidences selon...

Background:Maize lethal necrosis (MLN) disease continues to reduce the productivity of maize drastically threatening food security in the affected regions. It continues to cause yield loss of 30-100 percent in farmers' fields, depending on the time of infestation which is valued at $198 million in Kenya. This has not only threatened regional trade, but also seed industry. It has been reported in the major maize belts of Uasin Gishu, Trans-Nzoia, Bomet, Narok and Nandi Counties. MLN is caused by the synergistic interaction between Sugarcane Mosaic Virus (SCMV) and Maize Chlorotic Mottle Virus (MCMV). The disease has then spread to other Eastern and Central African countries with devastating food security and economic consequences. Objectives:This study highlights result after screening selected maize inbred lines for resistance to MLN, SCMV and MCMV in identifying promising lines for integration into the breeding program for MLN resistance. Methods:Sixty-five (65) maize genotypes were artificially inoculated using virus strains collected from Bomet County in Kenya at 3-4 leaf stage. Data on disease severity and incidence, AUDPC and flowering were recorded. Results:From the result, the inbred lines had significant differences for SCMV, MCMV and MLN reactions. Based on Area Under Disease Progress Curve (AUDPC) score and ELISA analysis, genotypes MLN001 and MLN006 have the lowest score of 270, whereas OH28 had a maximum at 1259 under MCMV. Genotypes MLN042 and MLN041 were identified as the most promising sources of resistant against SCMV. However, no genotype was identified to have acceptable levels of tolerance to MLN, but MLN001 and MLN013 were identified as the best performers under MLN. This study also validated the presence of MLN tolerance in MLN013 (CKDHL120312) and MLN001 (CKDHL120918) as earlier reported by CIMMYT. These tolerant genotypes are now serving as donors in the introgression of the tolerance into the Kenyan adapted maize backgrounds and development of improved MLN tolerant varieties. This will go a long way in restoring and ensuring sustainable maize productivity in improving the livelihoods of the smallholder farmers who form 75% of the major maize producers in Kenya.The identified inbred lines would be recommended for use in varietal development, MLN management and to enhance maize productivity, in the MLN endemic regions and further research in understanding the mode of gene action for MLN tolerance.

Maize (Zea mays L.) productivity in the sub‐Saharan Africa is constrained by biotic and abiotic stresses that reduce yield. In the region, one of the most serious abiotic factor is frequent intermittent droughts, which has been attributed to climate change. The purpose of this paper was to use on‐farm demonstration studies and farmer field days to demonstrate new drought mitigation technology and provide information on how small farmers can reduce yield losses. A total of 4814 demonstration plots of 39 DroughtTEGO maize hybrids and 19 commercial check hybrids were established in 17 counties across the low‐to‐mid‐altitude maize‐growing agroecologies of Kenya between 2015 and 2017. A total of 246 field‐day workshops were conducted. Combined analyses across years and locations showed that top five DroughtTEGO hybrids increased maize yields 33 to 54% (5.5–6.3 Mg ha−1) relative to conventional hybrids. The highest yield advantage of DroughtTEGO hybrids over commercial checks was observed in the drier lower eastern region in Kenya. Farmers particularly women, preferred the DroughtTEGO hybrids because of the stay‐green character, whiteness of flour (milling quality), root lodging resistance, drought‐tolerance and shelling percentage. Results from this study suggested that smallholder farmers can reduce the impact of drought by seeding drought‐tolerant maize hybrids. Core Ideas High yields and farmer‐preferred traits determine adoption of new varieties. Conducting on‐farm demonstrations can overcome adoption barriers. Planting of drought‐tolerant hybrids mitigates drought stress for smallholder‐farmers.

A study was conducted using maize samples collected from different agroecological zones of Kenya (n = 471) and Tanzania (n = 100) during the 2013 maize harvest season to estimate a relationship between aflatoxin B1 concentration and occurrence with weather conditions during the growing season. The toxins were analysed by the ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method. Aflatoxin B1 incidence ranged between 0–100% of samples in different regions with an average value of 29.4% and aflatoxin concentrations of up to 6075 µg/kg recorded in one sample. Several regression techniques were explored. Random forests achieved the highest overall accuracy of 80%, while the accuracy of a logistic regression model was 65%. Low rainfall occurring during the early stage of the maize plant maturing combined with high temperatures leading up to full maturity provide warning signs of aflatoxin contamination. Risk maps for the two countries for the 2013 season were generated using both random forests and logistic regression models.

Cowpea is popular in Eastern Kenya where it is attractive to farmers because of its high economic value and the belief that it does not require many external inputs. Farmers are however discouraged to grow the crop in this region due to massive attack by a parasitic weed Alectra vogelii (Benth). Yield losses due to A. vogelii have being estimated to range from 50 to 100% in Mbeere, Kitui and Makueni districts. No single method however is available to farmers in these regions in control of the parasitic weed. Combining several control methods, as in the management of Striga spp in Western Kenya should be a sustainable option. Field studies were conducted in 2010 and 2011 at Kenya Agricultural Research Institute (KARI), Kiboko farm to determine the response of 143 cowpea genotypes to Alectra infestation. The aim for the study was to identify resistant genotypes that could be used in breeding programme. Significant differences were observed amongst cowpea genotypes in days to first Alectra emergence, number of Alectra shoots emerged at 6, 8, 10 and 12 week after planting and grain yield. Cowpea genotypes Kir/Nya-005 and Mbe/Mach-022 showed complete resistance to Alectra while Ken-Kunde, M66 and K80 (all commercial varieties) supported the highest number of Alectra shoots. Grain yield loss in the three susceptible varieties was 80, 79 and 50% respectively. On the other hand, Sia/Cia-004, Mbe/Mach-014 and Kib-006 had high grain yields despite the high number of Alectra shoots present. There was a strong correlation (r =-0.57) between grain yield and number of Alectra shoots emerged at 12 weeks after planting. A significant negative (r =-0.37) correlation was also obtained between pod number per plant and number of emerged Alectra shoots at 12 weeks after planting. This negative correlation proves the high accumulation dry matter in the cowpea roots at the expense of the pods thus decreasing grain yield. This information showed that there is sufficient genetic variability in the cowpea genotypes studied, which can be exploited in breeding improved cowpea varieties for resistance to A. vogelii in Kenya. A great progress towards developing improved cowpea variety that meets farmer's preferences with durable resistance to A. vogelii can be achieved if the genes from the resistant and tolerant local cowpea cultivars identified in this study could be introgressed into the adapted susceptible improved varieties. This will increase the potential impact of adoption of resistant cowpea varieties in the zones.

Beans (Phaseolus vulgaris L.) are important legumes in the semi-arid areas of Eastern Kenya. But their production is constrained by water stress within the season and between seasons. A field trial was conducted in the short rains in the year 2011 (October to December) and long rains of 2012 (March to June) at KARI-Katumani (10 35'S and 37014'E, and 1560 metres above mean sea level) to determine the effect of on soil moisture and soil nutrients on grain yield of three market -preferred bean genotypes; namely: Katumani bean 1, NUA 1 and NUA 4. The experiment was conducted using a randomized block design with three replications with treatments in split plot arrangement. Results showed that bean grain yields of Kat B1 and NUA1 grown on tied ridges with manure at 5 tons ha-1 produced significantly (P<0.05) higher yields than furrow or flat tillage beans with and without manure in the short rains of 2011. In the long rains of 2012, Kat B1 and NAU1 beans grown on tied ridges with manure out yielded all the other treatments. In the same season, grain yield of NUA 4 grown on tied ridges with manure, was higher than beans grown on open furrows, flat tillage with and without manure. In both seasons, Kat B1 produced significantly higher grain yields than all the other genotypes except NUA 4 during the short rains of 2011.

Impact of DroughtTEGO ® maize hybrids on agricultural productivity and poverty reduction among small-scale maize farmers were analyzed using 642 households in Kenya. The Water Efficient Maize for Africa (WEMA) project coordinated by the African Agricultural Technology Foundation (AATF) developed the varieties. While on-farm production output and farmers' testimonies indicate significantly high productivity over other varieties, a rigorous assessment of impacts at household level is missing. Direct comparison of maize income, total household income and poverty indices shows significant differences between adopters and non-adopters. However, since the observed estimates can be due to differences in both observable and non-observable characteristics between adopters and non-adopters, we cannot have any causal interpretation. This study, therefore, utilized the counterfactual outcome framework based on propensity score methods (PSM) to control for such differences. The results of PSM showed that adoption of DroughtTEGO ® maize varieties led to significant increase in maize income by 82%, total income by 75%, and reduced the depth of poverty by 46-point margins. The study recommends formulation and implementation of appropriate policies to improve the adoption of DroughtTEGO® hybrid maize varieties across the country.