Eric Danquah

Diversity analysis of sweet potato ( Ipomoea batatas [L.] Lam) germplasm from Burkina Faso using morphological and simple sequence repeats markers

Collecting and characterizing plant material has been basic for crop improvement, and diversity has long been seen as vital for rational management and use of crops. Thirty (30) morphological characters and thirty (30) simple sequence repeat (SSR) markers were used to assess the diversity among 112 sweet potato (Ipomoea batatas [L.] Lam) cultivars in Burkina Faso and to develop a core collection. Eight morphological characters were able to differentiate the 112 accessions and to identify 11 duplicates while 28 SSR markers were more informative in discriminating the accessions and to identify five duplicates. The diversity assessment using the two approaches revealed high diversity with a coefficient of 0.73 using the phenotypic data, while moderate diversity with a coefficient of 0.49 was obtained using the SSR markers. These results show no correlation between the two approaches (with dissimilarity index of 0.95). A core collection was constituted using the SSR based data while the eight discriminative phenotypic descriptors will be used in the identification of cultivars.

Diversity in 113 cowpea (Vigna unguiculata (L) Walp) accessions assessed with 458 SNP markers

Single Nucleotide Polymorphism (SNP) markers were used in characterization of 113 cowpea accessions comprising of 108 from Ghana and 5 from abroad. Leaf tissues from plants cultivated at the University of Ghana were genotyped at KBioscience in the United Kingdom. Data was generated for 477 SNPs, out of which 458 revealed polymorphism. The results were used to analyze genetic dissimilarity among the accessions using Darwin 5 software. The markers discriminated among all of the cowpea accessions and the dissimilarity values which ranged from 0.006 to 0.63 were used for factorial plot. Unexpected high levels of heterozygosity were observed on some of the accessions. Accessions known to be closely related clustered together in a dendrogram drawn with WPGMA method. A maximum length sub-tree which comprised of 48 core accessions was constructed. The software package structure was used to separate accessions into three groups, and the programme correctly identified varieties that were known hybrids. The hybrids were those accessions with numerous heterozygous loci. The structure plot showed closely related accessions with similar genome patterns. The SNP markers were more efficient in discriminating among the cowpea germplasm than morphological, seed protein polymorphism and simple sequence repeat studies reported earlier on the same collection.

Farmer and consumer preferences for rice in the Ashanti region of Ghana: Implications for rice breeding in West Africa

Rice has become an important staple in Ghana in recent years but most consumption is met by imports. In this study, farmers’ preferences for rice varietal traits especially grain quality and the relationship of grain quality with consumer acceptability of locally produced rice was investigated in the Ashanti region of Ghana. Both formal and informal survey approaches were employed to collect data. The farmers preferred rice varieties with high yield potential and excellent grain quality. Jasmine 85 was the most popular variety because of its good taste and pleasant aroma. Other important traits that farmers consider in choosing a variety included plant height, threshability, disease resistance and weed competitiveness but these were site specific. Most consumers preferred imported to locally produced rice because the former had better appearance, cooking and eating qualities. Surprisingly, consumers’ perceptions on various grain quality attributes were generally lower than those of farmers. However, quality attributes were considered by both farmers and consumers to be important for making choices for rice varieties and their specific preferences largely coincided. Most consumers and farmers prefer long grain aromatic rice that cooks soft and fluffy. The results of the survey emphasizes the need for Rice breeders in Ghana and the West African sub-region in general to focus more on breeding for improved grain quality in addition to high yield potential and tolerance to biotic and abiotic stresses.

GENETIC CONTROL OF SEED SIZE IN COWPEA (Vigna unguiculata (L.) Walp)

Seed size contributes to yield and it is also a consumer trait of cowpea in Ghana and other parts of the world. Ghanaian consumers tend to prefer large seeded cowpea to small sizes although, Ghanaian varieties have smaller seeds compared to the imported types. This might be a contributing factor to high importation of cowpea to Ghana. To breed cowpeas with large grains, it is paramount to understand the inheritance of the trait. Generation mean analysis was performed to estimate gene actions on seed size of cowpea using CB27 and Gh3710 as the large and small seeded parents respectively. It was observed that eight genes control seed size and that small seed is partially domi- nant over large seed. The estimated broad sense heritability was 84% while the narrow sense was 35%. Both additive and non-additive genes with their interactions in the exception of additive - additive had significant effect on seed size inheritance in cowpea. The inheritance of seed size was observed to be complex, it was suggested that combinations of methods such as single seed descent and backcross methods with selection from early generations through advanced level would help improve seed size of cowpea.

Identification of Pro-vitamin A Cassava (Manihot esculenta Crantz) Varieties for Adaptation and Adoption through Participatory Research

In spite of diligent efforts by National Root Crops Research Institute (NRCRI) Umudike and International Institute of Tropical Agriculture (IITA) to make Nigeria the largest producer of cassava in the world, the adoption rate of elite cultivars by farmers is about 40% and that is unacceptable. In addition, all cassava cultivars presently grown in Nigeria are low in essential minerals, vitamins, and protein content, and high in cyanogenic content. Cassava with yellow roots contains elevated levels of β-carotene (pro-vitamin A), an essential nutrient, but they are not commonly grown in Nigeria. Because farmers select cultivars based on multiple criteria, participatory rural appraisal and selection are essential for a successful adoption of new improved varieties. A participatory rural appraisal (PRA) and sensory evaluation were conducted in Abia, Imo, and Ebonyi states of Nigeria to assess farmers’ preferences for pro-vitamin A cassava. Some of the farmer-preferred traits included high yield, early maturity, tolerance to pests and diseases, sweetness, high amount of dry matter (DM) content, easy peeling, marketable roots, and roots that keep long in the ground without decaying. High pro-vitamin A cassava cultivars TMS 01-1368, TMS 05-1636, and TMS 05-0473 were better than farmers’ cultivar NR 8082, because of their color, high premium price, nutritional value, texture, among others, and were selected for adoption.

Genetic diversity among INERA maize inbred lines with single nucleotide polymorphism (SNP) markers and their relationship with CIMMYT, IITA, and temperate lines.

BackgroundGenetic diversity provides the capacity for plants to meet changing environments. It is fundamentally important in crop improvement. Fifty-nine local maize lines developed at INERA and 41 exotic (temperate and tropical) inbred lines were characterized using 1057 SNP markers to (1) analyse the genetic diversity in a diverse set of maize inbred lines; (2) determine the level of genetic diversity in INERA inbred lines and patterns of relationships of these inbred lines developed from two sources; and (3) examine the genetic differences between local and exotic germplasms.ResultsRoger’s genetic distance for about 64% of the pairs of lines fell between 0.300 and 0.400. Sixty one per cent of the pairs of lines also showed relative kinship values of zero. Model-based population structure analysis and principal component analysis revealed the presence of 5 groups that agree, to some extent, with the origin of the germplasm. There was genetic diversity among INERA inbred lines, which were genetically less closely related and showed a low level of heterozygosity. These lines could be divided into 3 major distinct groups and a mixed group consistent with the source population of the lines. Pairwise comparisons between local and exotic germplasms showed that the temperate and some IITA lines were differentiated from INERA lines. There appeared to be substantial levels of genetic variation between local and exotic germplasms as revealed by missing and unique alleles.ConclusionsAllelic frequency differences observed between the germplasms, together with unique alleles identified within each germplasm, shows the potential for a mutual improvement between the sets of germplasm. The results from this study will be useful to breeders in designing inbred-hybrid breeding programs, association mapping population studies and marker assisted breeding.

Diversity assessment of drought tolerant exotic and adapted maize (Zea mays L.) inbred lines with microsatellite markers

Knowledge about the genetic diversity within a germplasm allows for a more effective and efficient use of resources for crop improvement programs. Diversity assessment of 48 tropical drought-tolerant maize inbreds, 24 each from CIMMYT and IITA, was carried out with microsatellite markers to determine the genetic divergence between the two groups of maize inbred lines. Eighty-one polymorphic SSR markers were used for the assessment. Results showed that the average number of alleles per locus was 3.7. The mean polymorphic information content (PIC) was 0.51 whereas the average modified Roger’s genetic distance (MRD) was 0.49. The mean genetic distance estimates between the CIMMYT and IITA lines were higher than the mean genetic distance among IITA lines or among CIMMYT lines. The average linkage cluster analysis separated the lines into two broad groups along institutional lines. The observed sub-groups within each main group were reflections of the relationships of the lines based on pedigree records. The FST value of 19.5% reflects a high level of genetic differentiation between the two groups of lines. The results highlighted the presence of appreciable genetic divergence between CIMMYT and IITA lines that can be exploited for superior hybrid maize development.

Conversion of Microsatellite Markers to Single Nucleotide Polymorphism (SNP) Markers for Genetic Fingerprinting of Theobroma cacao L.

The majority of the worlds cacao for chocolate manufacture is produced in West Africa. Cocoa breeding programs in West Africa need genetic markers to reduce the time needed for improving cocoa by screening seedlings for the presence of the markers rather than mature plants for the phenotypic traits (i.e., marker-assisted selection [MAS]). For MAS to be successful, the breeder must have both access to markers linked to desired traits and a convenient marker-assay system that can be performed locally. In this study, microsatellite markers that flanked disease resistance quantitative trait loci (QTL) but could not be assayed conveniently in West Africa were converted using a genome walking method into single nucleotide polymorphism (SNP) markers that could be assayed locally. The SNP and microsatellite markers were equally effective in identifying off-types in two different mapping populations of cacao. Also, SNPs cast doubt on whether all microsatellite markers are identical by descent.

Selection of Drought Tolerant Maize Hybrids Using Path Coefficient Analysis and Selection Index

BACKGROUND In drought-prone environments, direct selection for yield is not adequate because of the variable environment and genotype x environment interaction. Therefore, the use of secondary traits in addition to yield has been suggested. The relative usefulness of secondary traits as indirect selection criteria for maize grain yield is determined by the magnitudes of their genetic variance, heritability and genetic correlation with the grain yield. MATERIALS AND METHODS Forty eight testcross hybrids derived from lines with different genetic background and geographical origins plus 7 checks were evaluated in both well-watered and water-stressed conditions over two years for grain yield and secondary traits to determine the most appropriate secondary traits and select drought tolerant hybrids. RESULTS Study found that broad-sense heritability of grain yield and Ear Per Plant (EPP) increased under drought stress. Ear aspect (EASP) and ear height (EHT) had larger correlation coefficients and direct effect on grain yield but in opposite direction, negative and positive respectively. Traits like, EPP, Tassel Size (TS) and Plant Recovery (PR) contributed to increase yield via EASP by a large negative indirect effect. Under drought stress, EHT had positive and high direct effect and negative indirect effect via plant height on grain yield indicating that the ratio between ear and plant heights (R-EPH) was associated to grain yield. CONCLUSION Path coefficient analysis showed that traits EPP, TS, PR, EASP, R-EPH were important secondary traits in the present experiment. These traits were used in a selection index to classify hybrids according to their performance under drought. The selection procedure included also a Relative Decrease in Yield (RDY) index. Some secondary traits reported as significant selection criteria for selection under drought stress were not finally established in the present study. This is because the relationship between grain and secondary traits can be affected by various factors including germplasm, environment and applied statistical analysis. Therefore, different traits and selection procedure should be applied in the selection process of drought tolerant genotypes for diverse genetic materials and growing conditions.

Identification of CMS maintainers and restorers for hybrid rice development in Ghana

ABSTRACT The cytoplasmic-genetic male sterility is the most widely used system for hybrid rice (Oryza sativa) seed production. It requires three lines: the two hybrid parents (A and R lines) and a third line (maintainer (B line)), which maintains the sterility of the female parent during seed increase. Studies were undertaken to identify maintainers and restorers for introduced cytoplasmic male sterile (CMS) lines using simple sequence repeat (SSR) markers and testcrosses. Molecular screening with SSR marker RM6100 grouped the assembled inbred lines into 30 potential restorers and 55 potential maintainers. One maintainer (WAS 127 -12-1-6-3-1) and 16 restorers were confirmed by testcrosses. WAS 127-12-1-2-3 had higher grain yield per plant in crosses with CMS1 (IR69625A) than the local checks (AgraRice and Jasmine 85) and could be used as a restorer to develop a locally adapted, high-yielding hybrid. Conversion of WAS 127 -12-1-6-3-1 into a local CMS line was stopped because of sterility instability in the BC1F1 generation. Continued testcrosses to the set of identified potential maintainers could help identify a stable one that can successfully be converted into a locally adapted CMS line.