Evaluation and phenotypic plasticity of taro [Colocasia esculenta (l.) Schott.] genotypes for nutrient and anti-nutrient composition

The study was carried out to determine the nutritional and anti-nutritional composition of taro genotypes and also determine the phenotypic plasticity of the genotypes in two agro ecological zones in Ghana. The towns and zones were Bunso in the semi deciduous forest (an upland) and Tano Dumasi in the forest savannah transition agro-ecological (a waterlogged area) zone in the Eastern and Ashanti regions respectively.Two (2) freshly harvested corms of each genotype from each location were assessed for their nutritional (moisture, protein, carbohydrate, ash and fat) and anti-nutritional (phytate, oxalate and tannin) composition Data collected were subjected to analysis of variance and AMMI analysis using GenStat 12 edition to assess the effect of genotype, environment and their interaction on the traits studied. Phenotypic plasticity for the genotypes and the traits studied was also calculated. Pearson correlation was also conducted to assess the relationship between the traits studied. There were significant differences among the genotypes for nutrient and anti-nutrient composition except for percentage fat, indicating enough genetic variability among the genotypes, giving room for good selection progress for development of taro varieties. A higher magnitude of the environment over genotype and genotype by environment interaction observed indicates the influence of environment in the expression of the nutritional and anti-nutritional traits. Observed varied phenotypic plasticity among the genotypes for the nutrient and anti-nutrients composition also indicates varied adaptation of the genotypes to the environment. Genotypes BL/SM/115, CE/MAL/32 and CE/IND/16 and hybrids KAO19 × CE/MAL/32 and CE/IND/16×KAO19, CE/IND/16 × BL/SM/10, and CE/IND/16 × BL/SM/115 which recorded high nutrients and low anti-nutrients content and were stable across the environments can be released to farmers for cultivation. They could also be included in breeding programs for the development of enhanced nutritional quality of taro in Ghana.

Genotype by Phytophthora colocasiae isolate interaction in breeding for resistance to taro [Colocasia esculenta var esculenta (L.) Schott] leaf blight disease in Ghana

Two experiments were undertaken to evaluate the resistance of 5 parents and 20 hybrids of dasheen taro (n = 25) developed through the diallel method to Phytophthora leaf blight disease which is also known as taro leaf blight disease (TLBD). The field experiment which was laid out in Randomized Complete Block Design with 3 replications assessed the disease incidence (%) and disease severity index (DSI%) among the genotypes planted in three (3) agro-ecological zones in Ghana. In the laboratory the parents and hybrids were inoculated with three (3) Phytophthora colocasiae isolates from Dormaa Ahenekro, Tano Dumasi and Bunso in the Bono, Ashanti and Eastern regions of Ghana respectively and the diameter of lesions formed on the leaves after five days of inoculation were measured. Significant differences (p < 0.05) among the parents and hybrids for resistance to the Phytophthora colocasiae isolates, TLBD incidence (%) and DSI (%) in the field were observed making room for selection for further breeding for resistant varieties of dasheen taro. The isolate effect and genotype by isolate interaction effect were not significant (p > 0.05) indicating the similarity of the isolates' virulence and pathogenicity and therefore any of the isolates identified can be used to screen for resistance to TLBD in Ghana. Hybrids BL/SM/115 × BL/SM/10, BL/SM/115 × CE/MAL/32, CE/MAL/32 × BL/SM/10, CE/MAL/32 × CE/IND/16 and CE/IND/16 × BL/SM/115 and parent CE/IND/16 were observed to have no disease incidence with corresponding zero DSI (%) making them highly resistant and therefore can further be field evaluated and be recommended to farmers for cultivation. The highly significant and positive predictive value for TLBD incidence and DSI (%) based on the lesion area on leaf discs suggests that resistant genotypes of TLBD can be selected at the laboratory without spending long periods of time and money for evaluating genotypes in the field.

Combining Abilities and Heterotic Patterns among Early Maturing Maize Inbred Lines under Optimal and Striga-Infested Environments

Information on the general combining ability of inbred lines and the specific combining ability of hybrid combinations is crucial for successful hybrid development. The objectives of this study were to (i) determine the combining ability of thirty selected early maturing maize inbred lines under Striga-infested and optimal environments, (ii) classify the inbred lines into heterotic groups using the general combining ability effects of multiple traits (HGCAMT) and the single nucleotide polymorphism genetic distance (SNP- GD) methods, and (iii) assess the effectiveness of the heterotic grouping methods. One hundred and fifty single-cross hybrids were generated from the thirty inbred lines using the North Carolina Design II mating method. The hybrids and six local check varieties were tested across optimal and Striga-infested environments in Ghana and Nigeria in 2016 and 2017. The inheritance of grain yield was controlled by the non-additive gene action under both environments and the additive gene action across the two research environments. The non-additive gene action modulated the inheritance of measured traits under Striga-infested environments, except for the Striga damage syndrome rating at 8 weeks after planting. Maternal effects were observed for most traits in each environment and across environments. The inbred lines TZEI 127 and TZEI 40 exhibited significant and positive GCA male and female effects for grain yield under each environment and across the two research environments, indicating the presence of favorable alleles for yield improvements. The SNP-GD heterotic grouping method was identified as the most adequate in grouping the thirty inbred lines.

Genetic control of earliness in cowpea (Vigna unguiculata (L) Walp)

Global climate change is expected to further intensify the already harsh conditions in the dry savannah ecological zones of sub-Saharan Africa, posing serious threats to food and income security of millions of smallholder farmers. Breeding cowpea for improved earliness could help minimize this risk, by ensuring that the crops complete their lifecycle before the cessation of rainfall. In this study, we crossed two sets of cowpea lines showing contrasting phenotypes for earliness in terms of days to 50% flowering (DFF). One set of the lines comprised three extra-early parents (viz.: Sanzi-Nya, Tobonaa and CB27, 30-35 DFF), and the other set consisted of three early-to-medium maturity lines (viz.: Kirkhouse-Benga, Wang-Kae and Padi-Tuya, 42-45 DFF). The derived crosses and their parents were evaluated for key earliness-related traits at Nyankpala and Manga sites of CSIR-Savanna Agricultural Research Institute (SARI), Ghana. To unravel the genetic control of measured traits, we compared the appropriateness of Chi-square goodness of fit tests using classical Mendelian ratios, and frequency distribution (histogram)-related statistics such as skewness and kurtosis. The Chi-square test suggested a single dominant gene mode of inheritance for earliness, whereas the quantitative methods implicated duplicate epistasis and complementary epistatic gene actions. Our results show that coercing segregating lines to fit into classical Mendelian ratios to determine the genetic control of earliness could be misleading, due to its subjectivity. Thus, the genetic control of earliness in cowpea is governed by complementary and duplicate epistasis. The most applicable breeding approach for traits influenced by duplicate epitasis is selection of desirable recombinants from segregating populations developed from bi-parental crosses. Complementary epitasis, as found in the Wang-Kae × CB27 cross, could be exploited in developing improved extra-early lines through backcrossing. Heritability and genetic advance estimates were high for days to first flower appearance (DFFA) and days to 95 % pod maturity (DNPM) in the Padi-Tuya × CB27 and Kirkhouse-Benga x CB27 crosses, indicating that breeding for extra-earliness is feasible. CB27 could be a good donor for introgression of earliness into medium to late maturing improved cowpea varieties, because crosses developed from it had high heritability and genetic advance estimates.

High-density DArT-based SilicoDArT and SNP markers for genetic diversity and population structure studies in cassava (Manihot esculenta Crantz)

Cassava (Manihot esculenta Crantz) is an important industrial and staple crop due to its high starch content, low input requirement, and resilience which makes it an ideal crop for sustainable agricultural systems and marginal lands in the tropics. However, the lack of genomic information on local genetic resources has impeded efficient conservation and improvement of the crop and the exploration of its full agronomic and breeding potential. This work was carried out to obtain information on population structure and extent of genetic variability among some local landraces conserved at the Plant Genetic Resources Research Institute, Ghana and exotic cassava accessions with Diversity Array Technology based SilicoDArT and SNP markers to infer how the relatedness in the genetic materials can be used to enhance germplasm curation and future breeding efforts. A total of 10521 SilicoDArT and 10808 SNP markers were used with varying polymorphic information content (PIC) values. The average PIC was 0.36 and 0.28 for the SilicoDArT and SNPs respectively. Population structure and average linkage hierarchical clustering based on SNPs revealed two distinct subpopulations and a large number of admixtures. Both DArT platforms identified 22 landraces as potential duplicates based on Gower's genetic dissimilarity. The expected heterozygosity which defines the genetic variation within each subpopulation was 0.008 for subpop1 which were mainly landraces and 0.391 for subpop2 indicating the homogeneous and admixture nature of the two subpopulations. Further analysis upon removal of the duplicates increased the expected heterozygosity of subpop1 from 0.008 to 0.357. A mantel test indicated strong interdependence (r = 0.970; P < 0.001) between SilicoDArT and DArTSeq SNP genotypic data suggesting both marker platforms as a robust system for genomic studies in cassava. These findings provide important information for efficient ex-situ conservation of cassava, future heterosis breeding, and marker-assisted selection (MAS) to enhance cassava improvement.

Trait profile of maize varieties preferred by farmers and value chain actors in northern Ghana

Plant breeders' knowledge of precise traits preferred by variety users would accelerate varietal turnover and widen adoption of newly developed maize varieties in Ghana. The objective of this research was to provide empirical evidence of trait preferences of farmers and other actors in the maize value chain in northern Ghana, based on which research strategies for maize improvement could be formulated. Participatory rural appraisal was conducted in 2016 to determine key traits preferred by maize value chain actors across the three regions in northern Ghana. A total of 279 maize value chain actors were interviewed. Different scoring and ranking techniques were used to assess the maize traits preferred by the different actors. Participatory variety selection trials were also conducted in the Tolon, West Gonja, Binduri, and Sissala East districts in northern Ghana from 2014 to 2016. The mother-baby trial approach was used to evaluate eight hybrids with 3000 farmers. Data on yield and agronomic performance of the hybrids and farmer's selection criteria were collected. Data analyses were performed using GenStat Edition 16 and SPSS Edition 20 statistical packages. The participatory rural appraisal method identified farmers, input dealers, traders, and processors as the primary maize value chain actors in the study areas. Trait preferences of the different actors overlapped and revolved around grain quality including nutritional value, and stress tolerance and grain yield. Results of the participatory variety selection study revealed that across districts, farmers preferred high-yielding varieties with multiple cobs per plant, white grain endosperm color, and bigger and fully filled cobs. For the first time, our holistic assessment of the trait preferences of key actors of the maize value chain in northern Ghana revealed a comprehensive list of traits, which could be used by breeders to develop varieties that may be preferred by all value chain actors in northern Ghana.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13593-021-00708-w.

Mapping chromosomal regions associated with anther indehiscence with exerted stigmas in CRI-48 and Jasmine 85 cross of rice (Oryza sativa L)

Anther indehiscence in certain wide crosses combines male sterility with stigma exertion, a phenomenon that is desirable for hybrid rice seed production. This study sought to identify chromosomal region(s) that combine anther indehiscence with exerted stigmas. A mapping population consisting of 189 BC1F1 plants was derived from a cross between CRI-48 and Jasmine 85 and backcrossing the resulting F1 to Jasmine 85. Contrary to the three complementary genes mode of inheritance reported earlier, a single locus (AI6-1) was mapped on chromosome 6 at 27.4 cM for anther indehiscence with exerted stigmas through a mixed model-based composite interval mapping (MCIM). This locus was flanked by two single nucleotide polymorphism (SNP) markers, K_ID6002884 and K_ID6003341 within a range of 23.1-28.9 cM. The allele at the locus was contributed by the CRI-48 parent which has Oryza glaberrima ancestry. This locus is suggested to control anther indehiscence and stigma exertion through pleiotropic gene action or cluster of genes.

Identifying heterotic groups and testers for hybrid development in early maturing yellow maize (Zea mays) for sub-Saharan Africa

Identification of heterotic groups and efficient testers, which are important prerequisites for the development of outstanding hybrids, has been a major challenge to its success, especially for early and extra-early germplasm. This study was carried out to (a) identify the most efficient heterotic grouping method for classifying a set of inbred lines and (b) determine the efficiency of testers in classifying inbred lines into heterotic groups. A total of 205 hybrids obtained by crossing 41 inbred lines with five standard testers were evaluated together with five hybrid checks under drought, low soil nitrogen (N), Striga-infested and optimal environments in Nigeria between 2014 and 2016. The heterotic group's specific and general combining ability (HSGCA) method was more effective in classifying the inbred lines into heterotic groups. Testers TZEI 17 and TZEI 23 were the most efficient across environments and could be invaluable for classifying other lines into heterotic groups and assessing combining ability of maize inbreds. In addition, these testers and heterotic groups represent an invaluable resource for development of outstanding hybrids in sub-Saharan Africa (SSA).

Genetic diversity and population structure of early-maturing tropical maize inbred lines using SNP markers

Information on genetic diversity and population structure are very important in any breeding programme for the improvement of traits of interest and the development of outstanding products for commercialization. In the present study, we assessed the genetic diversity of 94 early-maturing white and yellow tropical maize inbred lines using single nucleotide polymorphism (SNP) markers. The larger number of SNP markers used in this study allowed a clearer inference of the population structure of the 94 inbred lines. Cluster analysis resolved the inbred lines into different clusters based on their pedigree, selection history and endosperm colour. However, three heterotic groups were revealed by population structure analysis, but additional field evaluation could be more informative to confirm the heterotic groups identified. Nevertheless, wide genetic variability existed among the inbred lines making them unique with the potential to contribute new beneficial alleles to maize breeding programmes in the tropics, especially in the West and Central Africa (WCA) sub-region.

MOLECULAR AND PHENOTYPIC RESISTANCE OF GROUNDNUT VARIETIES TO LEAF SPOTS DISEASE IN GHANA

Groundnut yield is constrained in most cases by early and lateleaf spots diseases. Selection and breeding for resistance will enhance yields. Therefore, this study was conducted in Crop Research Institute, Fumesua-Kumasi, Ghana to screen 20 groundnut varieties for leaf spots resistance using both molecular and phenotypic tools. Differences in disease incidence among individual plants, severity score, lesion diameter and defoliation across the 20 genotypes were highly significant (p

First Report and Molecular Characterization of DNA A of Three Distinct Begomoviruses Associated with Tomato Leaf Curl Disease in Ghana

Tomato leaf curl disease is reported to be widespread in Ghana and to cause severe yield losses (4). So far, the causal agent has not been identified. Thirty-three tomato (Solanum lycopersicum L.) samples with symptoms such as curling, yellowing, small leaves, and stunting were collected from the Ashanti Region, the main tomato-production area in Ghana, including three samples from Akumandan in the autumn of 2007 and 30 samples from Kumasi in the spring of 2008. The observed leaf curl disease incidence in the farmer's field in Kumasi was approximately 75%. Viral DNAs were extracted from the 33 samples and tested for the presence of begomoviral DNA-A, DNA-B, and associated satellite DNA by PCR with previously described primers (1,3). The expected 1.4-kb DNA-A begomovirus fragment was obtained from one of the samples from Akumadan and from 25 samples from Kumasi. DNA-B and DNA-beta were not detected by PCR. The 1.4-kb PCR products from all positive samples were cloned and sequenced. Sequence comparison by MegAlign software (DNASTAR, Inc., Madison, WI) showed three distinct virus groups. One isolate from each group was selected and specific primers were designed to complete the DNA-A sequence. The DNA-As of GH5-3 (group 1), GOTB2-2 (group 2), and GHK2 (group 3) isolates consisted of 2,803 (GenBank Accession No. EU350585), 2,794 (GenBank Accession No. EU847739), and 2,792 nt (GenBank Accession No. EU847740) respectively. All contain the geminiviral conserved nonanucleotide sequence TAATATTAC in the intergenic region and the six predicted open reading frames (ORFs V1, V2, C1, C2, C3, and C4). BLASTn analysis was conducted with geminivirus sequences available in the GenBank database at National Center for Biotechnology Information (Bethesda, MD). Further sequence comparisons were performed by Clustal V algorithm of MegAlign software with the representative isolates of begomovirus species reported by Fauquet et al (2) and the sequences that showed high scores in BLASTn search. The DNA-A sequence of isolate GHK2 from Kumasi showed highest sequence identity (96.5%) with Tomato yellow leaf curl Mali virus (TYLCMLV; GenBank Accesssion No. AY502934). The DNA-A sequence of GH5-3 and GOTB2-2 isolates had 87.5% sequence identity with each other. Both had highest sequence identities of 76.7 and 77.6%, respectively, with Tomato leaf curl Antsiranana virus, Madagascar (GenBank Accession No. AM701764). They constitute two distinct begomovirus species based on DNA-A sequence comparisons and the International Committee on Taxonomy of Viruses proposed species demarcation of 89% sequence identity. The names Tomato leaf curl Ghana virus for isolate GH5-3 and Tomato leaf curl Kumasi virus for isolate BOTB2-2 are proposed, respectively. To our knowledge, this is the first report of molecular characterization of begomoviruses associated with tomato leaf curl disease in Ghana and of the presence of three distinct tomato begomoviruses. This presence should be considered for recommending or developing stable begomovirus resistant tomato cultivars for Ghana. References: (1) R. W. Briddon et al. Mol. Biotechnol. 20:315, 2002. (2) C. M. Fauquet et al. Arch. Virol. 153:783, 2008. (3) S. K. Green et al. Plant Dis. 85:1286, 2001. (4) D. Horna et al., eds. Online publication. Int. Food Policy Res. Inst. PBS Policy Brief 2, 2007.