Genetic diversity among tropical provitamin a maize inbred lines and implications for a biofortification program

Insights into the diversity and relationships among elite breeding materials are an important component in maize improvement programs. We genotyped 63 inbred lines bred for high levels of provitamin A using 137 single nucleotide polymorphism markers. A total of 272 alleles were detected with gene diversity of 0.36. Average genetic distance was 0.36 with 56% of the pairs of lines having between 0.30 and 0.40. Eighty-six percent of the pairs of lines showed relative kinship values <0.50, which indicated that the majority of these provitamin A inbred lines were unique. Relationship pattern and population structure analysis revealed presence of seven major groups with good agreement with Neighbour Joining clustering and somewhat correlated with pedigree and breeding origin. Utilization of this set of provitamin A lines in a new biofortification program will be aided by information from both molecular-based grouping and pedigree analysis. The results should guide breeders in selecting parents for hybrid formation and testing as a short-term objective, and parents with diverse alleles for new breeding starts as a long-term objective in a provitamin A breeding program

Aflatoxin-producing fungi associated with pre-harvest maize contamination in Uganda

Open Access Article; Published online: 31 Oct 2019Maize is an important staple crop for the majority of the population in Uganda. However, in tropical and subtropical climates, maize is frequently contaminated with aflatoxins, a group of cancer-causing and immuno-suppressive mycotoxins produced by Aspergillus section Flavi fungi. In Uganda, there is limited knowledge about the causal agents of aflatoxin contamination. The current study determined both the aflatoxin levels in pre-harvest maize across Uganda and the structures of communities of aflatoxin-producing fungi associated with the maize. A total of 256 pre-harvest maize samples were collected from 23 major maize-growing districts in eight agro-ecological zones (AEZ). Maize aflatoxin content ranged from 0 to 3,760 ng/g although only around 5% of the samples contained aflatoxin concentrations above tolerance thresholds. A total of 3,105 Aspergillus section Flavi isolates were recovered and these were dominated by the A. flavus L morphotype (89.4%). Densities of aflatoxin-producing fungi were negatively correlated with elevation. Farming systems and climatic conditions of the AEZ are thought to have influenced communities’ structure composition. Fungi from different AEZ varied significantly in aflatoxin-producing abilities and several atoxigenic genotypes were identified. The extremely high aflatoxin concentrations detected in some of the studied regions indicate that management strategies should be urgently designed for use at the pre-harvest stage. Atoxigenic genotypes detected across Uganda could serve as aflatoxin bio-control agents to reduce crop contamination from fields conditions and throughout the maize value chain

APPLICATION OF MORPHO-ANATOMICAL TRAITS OF MAIZE PLANT TO QUALITY CONTROL AND QUALITY ASSURANCE IN MAIZE SEED SYSTEM

Good seed quality can be obtained through control of the entire seed production process. There are emerging issues in the seed sector due to seed quality in market. In many countries seed and planting materials available to farmers are often of insufficient quality, thus undermining the potential performance of crops. The objective this study was to use morpho-anatomical traits to determine the levels of maize hybrid seed purity on the market in Uganda. A total of 120 samples of four popular commercial maize hybrid were collected from agro-dealers in 13 districts, representing 3 seed companies\u2019 distribution network. The samples were planted and evaluated based on their descriptors, using an Alpha Lattice Design, with two replications at the National Crops Resources Research Institute (NaCRRI), Namulonge. Data were collected for 33 morpho-anatomical traits. Results showed significant (P&lt;0.05) differences within hybrids, and sources of seed among districts. Among the test materials, only Longe 9H had no significant (P&lt;0.05) difference within traits but others had some levels of significant (P&lt;0.05) differences. The principal component analysis of quantitative traits resulted in four components for each variety, with the explanation total of 53.3% for Longe 6H, 51.1% for Longe 7H, and 92.8% for Longe 9H and 39.1% for Longe 10%. There were varying levels of contamination of commercial hybrids based on morphoanatomical traits diversity within hybrids, compared to their descriptors for the traits evaluated. Hence, there is need to strengthen the quality control sub-sector for improved productivity at farmer levels.Des semences de bonne qualit\ue9 peuvent \ueatre obtenues en exer\ue7ant un control syst\ue9matique sur chacun des maillons du syst\ue8me de production semenci\ue8re. Le secteur semencier conna\ueet de plus en plus de difficult\ue9s, et ceci en raison de la qualit\ue9 des semences sur le march\ue9. Dans plusieurs pays, les semences disponibles pour les producteurs sont souvent de qualit\ue9 non satisfaisante, reduisant ainsi la performance des cultures. L\u2019objectif de l\u2019\ue9tude \ue9tait de se servir des caract\ue8res morpho-anatomiques afin de determiner le niveau purit\ue9 des semences de ma\uefs hybride sur le march\ue9 semencier en Ouganda. Au total 120 \ue9chantillons des quatre vari\ue9t\ue9es commerciales populaires de ma\uefs hybride ont \ue9t\ue9 collect\ue9s chez les distributeurs de semences dans 13 districts, repr\ue9sentant les r\ue9seaux de distribution de 3 compagnies semenci\ue8res. Les \ue9chantillons ont \ue9t\ue9 sem\ue9s et \ue9valu\ue9s en se basant sur leurs descripteurs. Le dispositive exp\ue9rimental Alpha Lattice a \ue9t\ue9 utilis\ue9, avec deux r\ue9p\ue9titions \ue0 l\u2019institut national de recherche des ressources culturales (NaCRRI), Namulonge. Les donn\ue9es de 33 caract\ue8res morphoanatomiques ont \ue9t\ue9 collect\ue9es. Les r\ue9sultats ont montr\ue9 des differences significatives (P&lt;0,05) ont \ue9t\ue9 observ\ue9es parmi les hybrides, ainsi que les sources des semences au sein des districts. Parmi les mat\ue9riels test\ue9s, seul Longe 9H n\u2019avait exhib\ue9 aucune difference significative (P&lt;0,05) des caract\ue8res \ue9valu\ue9s, mais certains ont des differences significatives \ue0 (P&lt;0,05). l\u2019analyse en composntes principales des traits quantitatifs a montr\ue9 quatre composantes pour chaque vari\ue9t\ue9, avec l\u2019ensemble de ces composantes expliquant 53,3% de la variation totale pour Longe 6H, 51,1% pour Longe 7H, 92,8% pour Longe 9H et 39,1% pour Longe 10%. Les niveaux de contamination \ue9taient variables, sugg\ue9rant la n\ue9cessit\ue9 de renforcer le sous-secteur de control de qualit\ue9 en vue d\u2019une meilleure productivit\ue9 au niveau des producteurs

Genome-wide diversity and structure variation among lablab [Lablab purpureus (L.) Sweet] accessions and their implication in a forage breeding program

Open Access Article; Published online: 19 Mar 2021Most orphan crops have not been fully sequenced, hence we rely on genome sequences of related species to align markers to different chromosomes. This hinders their utilisation in plant population improvement programs. Utilising the advances in the science of sequencing technologies, the population structure, relatedness, and genetic diversity among accessions can be assessed quickly for better exploitation in forage breeding programs. Using DArTseq technology, we studied the genetic and structural variation in 65 Lablab purpureus (L.) Sweet conserved gene-bank accessions using 9320 DArTseq-based SNPs and 15,719 SilicoDart markers. These markers had a low discriminating ability with mean polymorphic information content (P.I.C.) of 0.14 with DArTseq-based SNPs and 0.13 with SilicoDart markers. However, the markers had a high mean call rate of 73% with DArTseq-based SNPs and 97% with SilicoDart markers. Analysis of molecular variance revealed a high within populations variance (99.4%), indicating a high gene exchange or low genetic differentiation (PhiPT = 0.0057) among the populations. Structure analysis showed three allelic pools in variable clusters of ΔK = 3 and 6. Phylogenetic tree of lablab accessions showed three main groups with variable membership coefficients. Most pairs of accessions (40.3%) had genetic distances between 0.10 and 0.15 for SilicoDart markers, while for DArTseq-based SNPs, (46.5%) had genetic distances between 0.20 and 0.25. Phylogenetic clustering and minimum spanning analysis divided the 65 accessions into three groups, irrespective of their origin. For the first time, this study produced high-density markers with good genom coverage. The utilisation of these accessions in a forage program will base on the information from molecular-based grouping. The outcomes uncovered the presence of noteworthy measure of variety in Uganda, CIAT and ILRI accessions, thus demonstrating an opportunity for further marker-trait-association studies