Insights on the potential of RNA-Seq on improving pomological traits of African indigenous fruit trees: a mini review

Fruit tree improvement has taken great strides by roping in improved and efficient biotechnological tools to increase fruit yield and quality to meet local and export demands. For the past decade, the RNA-Seq tool has successfully been used in fruit tree improvement programs to identify genes, dissect complex traits, and understand different molecular pathways and differential expression of genes. However, despite their growing importance in food and nutrition security, medicinal uses, and climate change mitigation strategies, very little has been done to improve the pomological traits of African indigenous fruits, especially at the molecular level. African indigenous fruit trees exhibit unexplained variation in flowering, fruit load, fruit size, fruit ripening, fruit taste, fruit nutritional composition and shelf-life. The booming local commercial companies and export markets are demanding consistent quality indigenous fruits. This has necessitated the need for fast and effective tools that will hasten the understanding and improvement of fruiting qualities. The improvement of fruiting and fruit qualities will go a long way in accelerating the domestication and commercialization of African indigenous fruit trees. This review paper gives molecular biology insights on how RNA-Seq has been successfully used in fruit improvement of exotic fruits through gene identification, comparative transcriptome analysis under different conditions, and understanding molecular pathways that influence important pomological traits. The review article also unearths opportunities where RNA-Seq can improve our knowledge and improvement of undesirable traits common in African indigenous fruit

Hydropriming improves seed germination in horned melon (Cucumis metuliferus E. Mey. Ex Naudin) landraces

The global popularity of horned melon highlights the need of sound crop establishment processes, since uniform and quick seed germination has a substantial influence on crop yield and quality. Using a Completely Randomised Design (CRD) with a factorial structure, the effects of hydro priming durations (0, 8, 16, 24, 32, and 40 h) on seeds of two horned melon landrace (L1&L2) were investigated. Hydro priming had significant (P>0.05) influence on several germination indices (germination percentage, relativized percentage, mean germination rate, germination index, synchronization, duration to 50 % germination, mean daily germination, peak value, and germination value). Among the germination indicators tested, landrace (L2) exhibited a considerably stronger germination response than L1. The findings also reveal a curvilinear relationship between priming length and germination percentage, with 24 hours being greatest proportionately. The mean germination rate, germination index, mean daily germination, peak value of germination, and germination value all rose as the hydro priming duration increased. Primed seeds germinated more quickly than unprimed ones. With increasing priming duration, the synchronization index fell linearly. The interaction between landraces and hydro priming was not significant (P>0.05) for final seed germinated, relativized germination, and synchronization indices, but it had a significant impact on all other indices. Because the efficacy of hydro priming tends to lessen with extended soaking, we recommend using it for a maximum of 32 hours. Future study should concentrate on alternative priming chemicals and the applicability of various priming solutions for various agroecosystem

Effects of water stress at different growth stages on yield and yield components of common bean (Phaseolus vulgaris)

Common bean (Phaseolus vulgaris L.) has great potential for improving human nutrition due to its high protein content. However, water stress was found to be one of the major constraints to common bean production in Zimbabwe. A field experiment was therefore carried out at Agricultural Research Trust farm in early summer of 2004, and repeated at the same time in 2005, to determine the effect of water stress at different growth stages on grain yield and yield components of three common bean varieties. The experimental design was a 3×5 split-plot in a Randomised Complete Block Design; with water stresses as the main plot factor (withholding irrigation for a period of twenty-one days at; two weeks after emergence (WAE), four WAE, at flowering and two weeks after flowering (WAF) as well as non-stressed control) and the varieties in the subplot factor (Onyx, Pan 329 and Dark Red Kidney). Water stress significantly reduced grain yield (p<0.05) with flowering and two WAF stages being the most sensitive, and vegetative stage being the least sensitive. Water stress also produced significant effects (p<0.05) on yield components. Water stress during flowering and after flowering significantly reduced number of seed per pod and seed weight. For maximum yield, water stress must be avoided during flowering and pod-filling stages, so early planting is important under dry land planting

Assessment of genotype x environment interaction and pod yield evaluation of groundnut (Arachis hypogaea L.) genotypes in Zimbabwe

Groundnut is an important component of the diet of both rural and urban populations in the Sub-Saharan Africa. The national average pod yield is 0.25 t/ha which is far less than the global average. The diverse environmental conditions of Zimbabwe make selection and release of stable groundnut genotypes a challenge, mainly due to genotype x environment interaction (GEI). Twenty-five groundnut genotypes were evaluated to examine the level and type of GEI on pod yield. The genotypes were evaluated under multi-environmental yield trial conducted in (2013/14 summer season) at five environments. The objectives of the experiment were to determine the presence of GEI on pod yield stability of groundnut genotypes, to identify genotypes that are specifically or widely adapted. General combined analysis of variance (GenStat Version 14) at 5% significance level indicated that genotypes (G) were not significant (p = 0.153), environments (E) and genotype x environment interactions (GEI) were highly significant (P < 0.05) on pod yield. The environment influenced yield of the groundnut genotypes. Environment and genotype explained 58.8 and 6.1% respectively of the total treatment variance, whilst the genotype by environment interaction accounted for 35.1%, indicating that environment influenced a lot on the performance of the genotypes. High significant level of GEI indicates that some genotypes may be released for specific environments. Basing on the mean pod yield value from the combined (ANOVA) analysis of variance results, groundnut genotype G24 (3.34 t/ha, check variety) was the highest yielder, followed by G7 (3.31t/ha) and then G2, G14 and G11 (3.29, 3.25 and 3.02 t/ha respectively). The results indicate that the experimental genotypes have great potential to be released and grown on large scale production. Stability analysis based on one multivariate or various uni-variate parameters to extract more information on the GEI on pod yield stability of groundnut is recommended

A report on environmental impact and climate resilience building strategies

Weltfriedensdienst e.V. (Germany), Bread-for-the-World (Germany), Tudor Trust, (UK)

The development and release of maize fortified with provitamin A carotenoids in developing countries.

Micronutrient deficiencies have been identified as major public health problems affecting a large part of the world's population. Biofortification of staple crops like maize has been proposed as one of the most cost effective and feasible approaches to combat micronutrient deficiencies. Studies have shown that provitamin A from biofortified crops is highly bioavailable and has the capacity to improve vitamin A status of vulnerable groups. Most people in sub-Saharan Africa subsist on maize and many people may benefit from consumption of provitamin A carotenoid biofortified maize, especially women and children. With the exception of transgenic golden rice, biofortified crops have received considerable acceptance by most communities. Negative perceptions associated with yellow maize do not affect orange maize, which is, for example, well-liked in rural Zambia. With proper policy frameworks and full commercialization, provitamin A maize can address the problem of vitamin A deficiencies among poor nations with maize-based diets

Seed priming and water potential effects on germination and emergence of common bean (Phaseolus Vulgaris L.)

The aim of the study was to evaluate use of on-farm seed priming under artificial drought as a strategy to improve stand establishment in common bean grown under dry-land conditions. A laboratory experiment aimed at determining the effects of different water potentials (0, -10, -100, -200, -500, -1500 kPa) and different seed treatments (non-priming; 12-hour priming; 12-hour priming and 12-hour drying; 12-hour priming and 24-hour drying) on germination of three common bean varieties (PAN329, Contenta, Black bean). A field experiment was also carried out to determine the effects of different priming periods (0; 1; 2; 4; 8; 12; 16; 20 and 24 hours; 12-hour soaking and 12-hour drying; 12-hour soaking and 24-hour drying; 24-hour soaking and 12-hour drying; 24-hour soaking and 24-hour drying) on emergence of varieties PAN329 and Contenta. The highest germination rate was observed in water potentials of -100 and -200 kPa in PAN329 and Contenta while Black bean achieved higher germination at -500 kPa in the laboratory experiment. In the second experiment, soaking seed between 20 and 24 hours resulted in the highest emergence for PAN329 and Contenta respectively. It can be concluded that where water is limiting seed priming can be recommended to help improve stand establishment

Diallel analysis on variation of Verticillium wilt tolerance in upland cotton grown in Zimbabwe

Verticillium wilt disease causes significant losses to cotton yield and varietal development for resistance is critical in combating this threat. A study was carried out to determine the underlying genetic pattern controlling disease tolerance and identify suitable parental lines to use in varietal tolerance development. Five cotton varieties were crossed in a half diallel mating system to produce ten crosses and five selfed parental lines which were screened against Verticillium wilt by artificial inoculation. There were significant variations on the severity scores, vascular brown index scores, morphological and agronomical traits under Verticillium wilt pressure. The Verticillium wilt severity scores ranged from 1.22 to 3.07 and VBI scores from 0.78 to 2.77. The mean squares of general combining ability (GCA) for the various characteristics of the parents were significant and specific combining ability (SCA) of vascular brown index score. Three parental lines were identified as breeding material with good GCA, morphological and agronomical performance which were CRI-MS-1, SZ9314 and BC853. This study imply that varietal tolerance can be developed by incorporating genotypes with resistance genes in breeding programmes. Future work should focus on developing resistant varieties suitable for production in Verticillium wilt prone areas

Effects of water stress at different growth stages on yield and yield components of common bean (Phaseolus vulgaris)

Common bean (Phaseolus vulgaris L.) has great potential for improving human nutrition due to its high protein content. However, water stress was found to be one of the major constraints to common bean production in Zimbabwe. A field experiment was therefore carried out at Agricultural Research Trust farm in early summer of 2004, and repeated at the same time in 2005, to determine the effect of water stress at different growth stages on grain yield and yield components of three common bean varieties. The experimental design was a 3×5 split-plot in a Randomised Complete Block Design; with water stresses as the main plot factor (withholding irrigation for a period of twenty-one days at; two weeks after emergence (WAE), four WAE, at flowering and two weeks after flowering (WAF) as well as non-stressed control) and the varieties in the subplot factor (Onyx, Pan 329 and Dark Red Kidney). Water stress significantly reduced grain yield (p<0.05) with flowering and two WAF stages being the most sensitive, and vegetative stage being the least sensitive. Water stress also produced significant effects (p<0.05) on yield components. Water stress during flowering and after flowering significantly reduced number of seed per pod and seed weight. For maximum yield, water stress must be avoided during flowering and pod-filling stages, so early planting is important under dry land planting

Genotype x environmental interaction on seed cotton yield and yield components

Cotton yield and fibre quality parameters are dependent on the environment in which the crop is grown. A major challenge in crop genotype recommendations is genotype × environment interaction. The identification of cultivars with high adaptability and stability is one of the best ways to address this challenge. Genotype × Environmental interaction on Gosypium hirsutum was investigated. Ten genotypes were planted in a randomised complete block design with three replications. Collected data were subjected to Analysis of Variance (ANOVA) with genotype and location as factors. Additive Main Effect and Multiplicative Interaction model which combines standard analysis of variance with principal component analysis was used to investigate the genotype main effects, environment main effects and the GE interactions. Significant genotype × environment interactions existed for lint yield, boll weights, staple length, and fuzzy seed grade. There were no significant cultivar × site interactions on total seed cotton yield. Cotton cultivars respond differently to different growing conditions implying that, correct choice of varieties by growers for specific production conditions, must be a must to avoid losses due to genotype × environment interactions