Genetic variability, stability and heritability for quality and yield characteristics in provitamin A cassava varieties

Open Access Article; Published online: 25 Jan 2020Cassava is widely consumed in many areas of Africa, including Ghana, and is a major part of most household diets. These areas are characterized by rampant malnutrition, because the tuberous roots are low in nutritional value. Provitamin A biofortified cassava varieties have been developed by the International Institute for Tropical Agriculture, but adoption of these varieties in Ghana will largely depend on their agronomic performance, including fresh root yield, dry matter content, resistance to major pests and diseases, mealiness, starch content and the stability of these traits. Eight provitamin A varieties with two white checks were planted in three environments for two seasons to determine stability and variability among the varieties for important traits. There were significant variations in performance between varieties and between environments for cassava mosaic disease, root number, fresh root yield and starch content. High broad-sense heritability and genetic advance were observed in all traits, except for storage root number, and could be exploited through improvement programs. This study identified the best performing enhanced provitamin A varieties for traits that are key drivers of variety adoption in Ghana. In view of this, some varieties can be recommended for varietal release after on-farm testing. The study also showed the possibility of tapping heterosis after careful selection of parents

Assessing arthropod pests and disease occurrence in cassava (Manihot esculenta Crantz) and cowpea (Vigna unguiculata L. Walp) intercropping system in the Ashanti Region, Ghana

On-station trials were conducted at CSIR-Crops Research Institute’s research farms at Kwadaso and Ejura, Ashanti Region, Ghana, during 2010/2011 cropping season, to assess the pests and disease occurrence in cassava-cowpea intercrop farming systems and their effect on yield of produce. Three improved cassava varieties and a local variety were intercropped with an improved cowpea variety, and cowpea only constituted the treatments. Abundance of Bemisia tabaci was comparable between sole cassava and cassava-cowpea intercrop, but was significantly less on the sole cowpea. The incidence and severity of cassava mosaic disease was higher on the local variety than on the improved varieties. Root yield of cassava did not differ between sole and intercropped cassava with cowpea. However, Kwadaso had higher root yield than Ejura. Dry grain yield of cowpea was similar at Kwadaso and Ejura for both sole and intercrop scenarios. This baseline information will be useful on disease and pests incidence in sole crop and cassava-cowpea intercropping system

EXPLOITATION OF GENETIC POTENTIAL OF SWEETPOTATO FOR END-USER TRAITS IMPROVEMENT

Sweetpotato ( Ipomoea batatas Lam) is a staple food globally, but it has remained underutilised resource in Ghana due to lack of consumer preferred cultivars. There is the need to develop staple-type sweetpotato cultivars which are preferred by consumers to increase sweetpotato use as a food security, health and industrial crop commodity in Ghana. This study was conducted to evaluate the breeding potential of sweetpotato germplasm for the development of farmer and consumer preferred varieties in Ghana. A total of 115 sweetpotato accessions were evaluated for genetic variability. Significant (P<0.01) differences were observed indicating genetic diversity. G x E was significant for all traits, except dry matter, sucrose, total sugar, and starch content. Phenotypic Coefficient of Variation (PCV) ranged from 4.78% for starch content to 63.40% for marketable root weight. Genotypic Coefficient of Variation (GCV) ranged from 4.07% for starch content to 55.35% for marketable root weight. Broad-sense heritability estimates varied from medium (0.61) to high (0.90) for all the traits, except for sucrose content. Predicted improvement over the means is 10 up to 105% for all traits, except starch (7.13%). This indicates sufficient useful genetic variation prospect which could be used to provide substantial improvement through selection of superior genotypes. The strong positive genetic association between dry matter and starch (r = 0.71), and strong negative relationship for sugar and dry matter (r = -0.77) and starch content (r = -0.99) indicates the possibility of developing non-sweet high dry matter sweetpotatoes, which are the preferred varieties in Ghana.La patate douce ( Ipomoea batatas Lam) est un aliment de base \ue0 l\u2019\ue9chelle mondiale, mais c\u2019est une ressource sousutilis\ue9e au Ghana en raison du manque de cultivars pr\ue9f\ue9r\ue9 par les consommateurs. Il est n\ue9cessaire de d\ue9velopper des cultivars de patate douce de type de base qui sont pr\ue9f\ue9r\ue9s par les consommateurs pour augmenter l\u2019utilisation de la patate douce comme la culture de la s\ue9curit\ue9 alimentaire, la culture de sant\ue9 et le produit industriel au Ghana. Cette \ue9tude a \ue9t\ue9 men\ue9e pour \ue9valuer le potentiel du mat\ue9riel g\ue9n\ue9tique du germeplasme de la patate douce pour le d\ue9veloppement des vari\ue9t\ue9s pr\ue9f\ue9r\ue9es par les agriculteurs et les consommateurs au Ghana. Un total de 115 germeplasmes de patate douce ont \ue9t\ue9 \ue9valu\ue9s pour la variabilit\ue9 g\ue9n\ue9tique. Des diff\ue9rences significatives de (P<0,01) ont \ue9t\ue9 observ\ue9es indiquant la diversit\ue9 g\ue9n\ue9tique. G x E \ue9tait important pour tous les traits, \ue0 l\u2019exception de mati\ue8re s\ue8che, le saccharose, le sucre total et la teneur en amidon. Coefficient Ph\ue9notypique de variation (CPV) variait de 4,78% pour la teneur en amidon \ue0 63,40% pour le poids de racine commercialisables. Coefficient g\ue9notypique de variation (CGV) variait de 4,07% pour la teneur en amidon \ue0 55,35% pour le poids de racine commercialisables. Coefficient g\ue9notypique de variation (CGV) variait de 7,60% pour la teneur en mati\ue8re s\ue8che \ue0 55,35% pour le poids de racine commercialisables. Estimations de l\u2019h\ue9ritabilit\ue9 au sens large variat de (0,61) moyen \ue0 (0,90) haut pour tous les traits, sauf pour la teneur en saccharose. L\u2019am\ue9lioration pr\ue9dite sur le moyen est de 10 \ue0 105% pour tous les traits, \ue0 l\u2019exception de l\u2019amidon (7,13%). Cela indique suffisamment la perspective de la variation g\ue9n\ue9tique utile qui pourrait \ueatre utilis\ue9 pour fournir une am\ue9lioration substantielle par la s\ue9lection de g\ue9notypes sup\ue9rieurs. Une forte relation g\ue9n\ue9tique positive entre la mati\ue8re s\ue8che et l\u2019amidon (r = 0,71), et une forte relation n\ue9gative pour le sucre et la mati\ue8re s\ue8che (r = -0,77) et la teneur en amidon (r = -0,99) indiquent la possibilit\ue9 de d\ue9velopper la patate douce qui est non sucr\ue9e, haute de mati\ue8re s\ue8che et qui sont les vari\ue9t\ue9s pr\ue9f\ue9r\ue9es au Ghana

Towards a collaborative research: A case study on linking science to farmers' perceptions and knowledge on Arabica coffee pests and diseases and its management

The scientific community has recognized the importance of integrating farmer's perceptions and knowledge (FPK) for the development of sustainable pest and disease management strategies. However, the knowledge gap between indigenous and scientific knowledge still contributes to misidentification of plant health constraints and poor adoption of management solutions. This is particularly the case in the context of smallholder farming in developing countries. In this paper, we present a case study on coffee production in Uganda, a sector depending mostly on smallholder farming facing a simultaneous and increasing number of socio-ecological pressures. The objectives of this study were (i) to examine and relate FPK on Arabica Coffee Pests and Diseases (CPaD) to altitude and the vegetation structure of the production systems; (ii) to contrast results with perceptions from experts and (iii) to compare results with field observations, in order to identify constraints for improving the information flow between scientists and farmers. Data were acquired by means of interviews and workshops. One hundred and fifty farmer households managing coffee either at sun exposure, under shade trees or inter-cropped with bananas and spread across an altitudinal gradient were selected. Field sampling of the two most important CPaD was conducted on a subset of 34 plots. The study revealed the following findings: (i) Perceptions on CPaD with respect to their distribution across altitudes and perceived impact are partially concordant among farmers, experts and field observations (ii) There are discrepancies among farmers and experts regarding management practices and the development of CPaD issues of the previous years. (iii) Field observations comparing CPaD in different altitudes and production systems indicate ambiguity of the role of shade trees. According to the locality-specific variability in CPaD pressure as well as in FPK, the importance of developing spatially variable and relevant CPaD control practices is proposed. (Résumé d'auteur