Stability for descriptors of Solanum aethiopicum Shum group (family Solanaceae)

The study is about Shum one of the four recognized morphological groups of the African eggplantSolanum aethiopicum Shum group is a nutrient-rich and income-generating crop enterprise in various sub-Saharan Africa countries. Despite its importance, the development of its improved varieties has not been prioritized. Until now, no field-based descriptor development reference for the crop is available for testing candidate varieties for distinctiveness, uniformity and stability. The purpose of this study is to identify morphological variables that provide identity of S. aethiopicum Shum group accessions across environments. With ten accessions across three test locations, it was observed that the highly polymorphic morphological variables were majorly vegetative and a few reproductive ones. They include plant height at flowering, plant canopy breadth, plant branching, petiole color, petiole length, leaf blade length, leaf blade width, leaf lobbing, leaf tip angle, flowering time, style length, fruit position, fruit flesh density, fruits per inflorescence and fruit flavor. A static stability analysis, a common selection technique for obtaining consistence in performance of genotypes, showed that accessions varied in their interaction with environments for different descriptors. The most statically stable accessions were 184P and 163P while the least stables were 168P, 148, 141, and 137. The findings indicate the potential for identifying unique and stable varieties of S. aethiopicum Shum group for the processing of official release to farmers

Amplicon sequencing identified a putative pathogen, Macrophomina phaseolina, causing wilt in African eggplant (Solanum aethiopicum) grown in Tanzania and Uganda

African eggplant (Solanum aethiopicum L.) is one of the most common traditional vegetables in Tanzania and Uganda, but its productivity is severely affected by wilt diseases caused by a number of pathogens. Plant stem and root samples were collected in several fields from many neighboring diseased and healthy plants of the Gilo group in Tanzania and from the Shum group in Uganda to identify putative pathogens causing wilt on African eggplants. Through amplicon sequencing of sampled diseased and healthy tissues, we identified putative causal pathogens for the wilt symptoms. Wilting of S. aethiopicum in Uganda is most likely caused by the bacterial pathogen Ralstonia solanacearum whereas, in Tanzania, wilt is most likely caused by the fungal pathogen Macrophomina phaseolina, infecting roots. Infection of stems by Fusarium solani may also contribute to the wilt symptoms in Tanzania. Further artificial inoculation under controlled conditions confirmed that M. phaseolina can cause typical wilting symptoms on S. aethiopcium genotypes. The discovery of different putative causal agents of wilt in the crop demonstrates the need for site specific etiological analysis of wilt before developing and implementing effective control methods. Further research is needed to confirm the results and develop appropriate management measures against specific wilt pathogens

Draft genome sequence of Solanum aethiopicum provides insights into disease resistance, drought tolerance, and the evolution of the genome

The African eggplant (Solanum aethiopicum) is a nutritious traditional vegetable used in many African countries, including Uganda and Nigeria. It is thought to have been domesticated in Africa from its wild relative, Solanum anguivi. S.aethiopicum has been routinely used as a source of disease resistance genes for several Solanaceae crops, including Solanum melongena. A lack of genomic resources has meant that breeding of S. aethiopicum has lagged behind other vegetable crops. Results: We assembled a 1.02-Gb draft genome of S. aethiopicum, which contained predominantly repetitive sequences (78.9%). We annotated 37,681 gene models, including 34,906 protein-coding genes. Expansion of disease resistance genes was observed via 2 rounds of amplification of long terminal repeat retrotransposons, which may have occurred ∼1.25 and 3.5 million years ago, respectively. By resequencing 65 S. aethiopicum and S. anguivi genotypes, 18,614,838 single-nucleotide polymorphisms were identified, of which 34,171 were located within disease resistance genes. Analysis of domestication and demographic history revealed active selection for genes involved in drought tolerance in both “Gilo” and “Shum” groups. A pan-genome of S. aethiopicum was assembled, containing 51,351 protein-coding genes; 7,069 of these genes were missing from the reference genome. Conclusions: The genome sequence of S. aethiopicum enhances our understanding of its biotic and abiotic resistance. The single-nucleotide polymorphisms identified are immediately available for use by breeders. The information provided here will accelerate selection and breeding of the African eggplant, as well as other crops within the Solanaceae family

Genetic and root growth studies in cassava (Manihot esculenta Crantz)

Cassava (Manihot esculenta Crantz) is a perennial tropical crop grown for its starch-containing tuberous roots. It is cultivated mainly by small-scale farmers and consumed daily by an estimated 500 million people. Cassava mosaic disease (CMD) has long been recognized as a major limiting factor to cassava production in Africa and severe epidemics hit Uganda in the late 1920’s and late 1980’s. Inspite of its importance as a major food crop it is the least researched major crop and many questions regarding its genetics are still unresolved. This thesis has therefore dealt with studies on: i) the effect of CMD on the genetic diversity of cassava in Uganda, ii) the composition of varieties and the genetic structure within and between varieties on small farms in Uganda, iii) the genetic basis of two agronomic important traits, cyanogenic glucoside potential (CNP) and dry matter content (DMC) in cassava roots, using quantitative trait loci (QTL) mapping and iv) the effect of nutrient availability on the growth and tuber formation. The outcome of these studies is relevant for developing strategies for breeding and gene conservation programmes. CMD did not have a strong selective effect on the genetic diversity of cassava in Uganda in spite of earlier reports on losses of varieties due to the latest CMD epidemic. However, a loss of rare alleles in areas with high CMD incidence in Uganda was found. The composition of varieties differed widely between villages and districts and the genetic variation was surprisingly large within varieties although the variation was larger among varieties. The like-named varieties in different villages were genetically similar, demonstrating farmers’ ability to differentiate and maintain the same variety over large areas. We detected two QTL on two different linkage groups controlling CNP and six QTL on four different linkage groups controlling DMC. One QTL for CNP and one QTL for DMC mapped near each other, suggesting pleiotrophy or linkage of QTL. In the root studies, production of storage roots was found to be regulated by nutrient availability and appeared to be positively affected by a gradually increasing limitation of mineral nutrients during the growth of the plants

Identification of growth stage specific watering thresholds for drought screening in Solanum aethiopicum Shum

This research article was published in Scientific Reports by Nature Research. It is available via DOI: https://doi.org/10.1038/s41598-020-58035-1Effective phenotyping for drought resistance is a pre-requisite for identification of modest crop varieties for farmers. For neglected and underutilized crops such as Solanum aethiopicum Shum group, no drought screening protocol based on rigorous iterations has been documented. A split-plot nested treatment structure was arranged in an experiment to identify growth stage-specific watering thresholds for this crop. Three plant growth stages (main plot; seedling, vegetative and flowering), watering regime at plant growth stage (2 regimes; well-watered and drought stressed) and day since last watering at plant growth stage were evaluated for soil moisture content (SMC), leaf wilting score (LWS), number of green leaves per plant (LPP) and leaf blade width (LBW). Highly significant differences (p < 0.001) were found at the different plant growth stages, watering regime (WR) within plant growth stage, and day within WR and plant growth stage. Under drought stress treatment, SMC declined exponentially at each stage. The earliest leaf wilting, reduction in LPP and LBW were generally observed at flowering followed by vegetative and slowest at the seedling stage. For future effective drought phenotyping studies in S. aethiopicum Shum and related crops, we recommend setting minimum drought stress treatments below 18% SMC at which the LWS is ≥2 at the vegetativeThis study was support by The World Academy of Sciences (TWAS), Grant Number 16-163 RG/BIO/AF/AC_I – FR3240293342 towards equipment for the project titled “Phenotyping water use efficiency in Solanum aethiopicum, Shum Group”. Co-funding was generous provided by the European Union through Forum for Agricultural Research in Africa (FARA) in a project ‘Enhancing nutrition security and incomes through adding value to indigenous vegetables in East and Central Uganda’ (FARA/PAEPARD-CRFII)

Accuracy of using leaf blade length and leaf blade width measurements to calculate the leaf area of Solanum aethiopicum Shum group

Leaf area is an important parameter when determining growth response under normal as well as stressed environments. No attempt had been made to come up with an affordable but accurate alternative of measuring leaf size in research neglected leafy vegetable crops. Other techniques such as use of leaf area meters are either destructive, expensive or both. A study was conducted to determine leaf area in like-shaped leaves of research neglected crop plants, taking case of S. aethiopicum Shum group (SAS) germplasm. Data was collected on 552 individual plants (including pure lines and hybrids) at eight weeks after planting where a third fully open leaf from top of each plant was considered. Leaf blade length (LBL) and leaf blade width (LBW) were linearly measured while leaf area (LA) was measured using a leaf area meter. This was followed by correlation and regression analysis of LA with LBL, LBW, and LBL + LBW. Correlation coefficients at p < 0.001 ranged between 0.84 and 0.92, 0.79 and 0.88, 0.86 and 0.95 for total germplasm, pure lines and hybrids, respectively. The coefficient of determination (R2) ranged between 0.72 and 0.92. The best prediction for LA was obtained with hybrid plants (LA = -165.82 + 5.38LBL + 16.17LBW) at R2 of 92%. The implication is that we can accurately and affordably predict LA from duo measurements of LBL and LBW in SAS as well as in other crops having similar leaf shapes

Compatibility barriers affecting crossability between Solanum aethiopicum and its relatives

Reproductive barriers are single most important impediment in conventional breeding of Solanum aethiopicum (Shum and Gilo) and its relatives. This study investigated compatibility barriers between S. aethiopicum and its relatives. A randomized complete block design and a full diallel mating method were used to evaluate floral phenology and compatibility of six genotypes at different floral stages. Parameters assessed include; anthesis, anther dehiscence, stigma receptivity, among others. Results showed that most flowers in anthesis per genotype were counted at 8:00am. Overall mean number of open flowers differed significantly (P 80%) although they differed significantly (P<0.01). Stigma receptivity averaged highest (3.31) for N11 and least (2.31) for In1. All genotypes exhibited self-compatibility; N11 averaged highest for fruit set (67.93%), seed per fruit (82) and F1 germination (79%). Crosses revealed moderate compatibility (50%); highest fruit were in N4xN11 (71.97%), seed N11xA1 (56) and F1 germination inN11x N4 (76.3%) respectively. In the crosses where In1 was a female parent 80% incompatibility was observed at fruit set whereas73% of crosses where E12 was a female parent set fruits without seed. Female functioning may be a major factor in observed incompatibility between S. aethiopicum and its relatives. To harness the potential of S. aethiopicum relatives, N11 and N4 can be advanced as female parents in wide hybridizations.This work was funded by The World Academy of Sciences (TWAS) and Swedish International Development Cooperation Agency (Sida) grant number 20-320 RG/BIO/AF/AC_G – FR3240314173

Farmers’ selection cues in cowpea for vegetable use in eastern Uganda

A participatory cowpea varietal selection was carried out in Eastern Uganda in Kumi district among farmers (n=30) in the sub-Counties of: Ongino, Kumi and Kanyum. A range of opinions were collected to identify farmers’ selection criteria based on different sensory attributes and their most preferred genotypes for vegetable use. A preference analysis was carried out to obtain quantitative preference scores of each plot. This was followed by organoleptic tests which included attributes like taste, aroma and texture of the genotypes at the vegetative and immature R4 stages. Focus group discussions (FGDs) were also held to find consensus of the independent evaluations made by individual farmers. Data for sixteen (16) cowpea genotypes were collected at the different above mentioned stages. Quantitative data were analyzed based on farmers’ scores made on the different evaluated attributes and ANOVA was used to provide mean differences between location, gender and genotype at a significant level of 5%. Preference score for each of the varieties tested was determined and presented. Data from FGDs were grouped, similarities and differences were later determined depending on their level of importance to the farmers. Significant differences (p<0.05) in farmer choices were observed for leaf taste, immature pod aroma, taste and texture; mature pod aroma, taste between farmer groups, age genotype and gender. Irrespective of age, gender, farmer group and genotype, farmers seemed to give more importance to the smooth texture, little hard leaves when chewing, sweet taste with a mild aroma (leaves) and a moderate aroma (pods). Majority (9%) of the farmers preferred Ebelat (landrace) at V4 stage; this was followed by Danila (8.7%). On the other hand, UCUCOW1 (13% at immature and 10.2% at mature cooked R4 stage) followed by Ebelat (9% and 9.8% for immature and mature R4 stage, respectively) were preferred by majority of the farmers. In terms of sensory attributes, farmers preferred genotypes with sweet taste, moderate aroma and tender texture. The information is a baseline for understanding key farmer selection criteria in utilization of cowpea as a vegetable which can be used in generating a demand-led variety design for the crop

Draft genome sequence of Solanum aethiopicum provides insights into disease resistance, drought tolerance, and the evolution of the genome

The African eggplant (Solanum aethiopicum) is a nutritious traditional vegetable used in many African countries, including Uganda and Nigeria. It is thought to have been domesticated in Africa from its wild relative, Solanum anguivi. S. aethiopicum has been routinely used as a source of disease resistance genes for several Solanaceae crops, including Solanum melongena. A lack of genomic resources has meant that breeding of S. aethiopicum has lagged behind other vegetable crops