44 research outputs found
Incidence and severity of cassava mosaic disease in farmer’s fields in Ghana
A survey of cassava mosaic disease (CMD) was carried out in Ghana from 2007-2008 to assess CMD incidence, infection type, severity and adult whitefly population. A total of 136 farmers’ fields across major cassava producing areas in the Brong Ahafo, Western, Northern, Ashanti and Volta regions were assessed. CMD was prevalent in most of the 136 fields surveyed. Frequently encountered local landraces were susceptible to the disease. CMD incidence reached 100% in farmers’ fields. Mean disease incidence ranged from 46% in the Ashanti region to 90% in the Western region of the country. CMD incidence averaged 66.0%, with cutting-borne infection and Whitefly-borne infections being 54.0% and 12.0%, respectively. CMD shoot symptom severity ranged from 2.0 to 3.7 in the farmers’ fields, with a mean of 2.9. Mean adult whitefly population was 0.47. The high prevalence of CMD requires a concerted effort in the management of CMD in the country
Chemical control of mango anthracnose disease in Ghana
AbstractSeven different fungicides were evaluated in-vitro and in the field for their efficacy against the causal agent and incidence and severity of mango anthracnose disease in Ghana. The recommended rates of Bendazim, (Carbendazim), Funguran (Copper hydroxide), Ivory (Mancozeb), Agriette +Ivory (Fosetyl-Al +Mancozeb), Sundomil (Mancozeb+Metalaxyl), Top Cop (Copper +flowable sulphur), Mirage (Prochloraz), Bendazim+Ivory and Funguran+Ivory were mixed with potato dextrose agar (PDA) and the radial mycelial growth of the pathogen was determined on these amended media. The fungicides were applied on fruit bearing trees in a commercial farm in the Yilo Krobo District after which the disease incidence, severity and percentage of exportable fruits were determined. The results showed that the pathogen was not able to grow on PDA amended with the fungicides. In the field, Bendazim and Funguran fungicides were able to suppress the disease to a large extent resulting in the highest percentage of exportable fruits. Prochloraz solution at both ambient temperature and 53 °C were able to completely eradicate the pathogen, and prevented development of postharvest anthracnose disease symptoms.Original scientific paper. Received 30 Apr 14; revised 23 Sept 14
Groundnut production constraints and farmers’ trait preferences: a pre-breeding study in Togo
Background
Groundnut is an important legume crop in Togo. However, groundnut yield has been steadily decreasing for decades as a result of lack of organized breeding program to address production constraints. Though, low yielding varieties and late leaf spot have been often reported as the most important constraints, there is no documented evidence. Identifying and documenting the major production constraints is a prerequisite for establishing a good breeding program with clearly defined priority objectives and breeding strategies. Thus, the objectives of this study were to identify groundnut production constraints and assess farmers’ preferred traits.
Methods
A participatory rural appraisal approach was used to collect data on agronomic practices, farmers’ preferences, and possible threats to production through individual and group interviews. Three regions and three villages per region were selected based on the representativeness of groundnut production systems. In each village, 20 farmers were randomly selected and interviewed; thus, a total of 180 farmers were interviewed. Content analysis was carried out for qualitative data and for quantitative data generated within and across regions, comparative descriptive statistics were carried out. Differences in perception and preferences were assessed using chi-square tests.
Results
The study has revealed that, though there were some variation across the regions, traits pertaining to yield such as pod yield (66.66%) and pod size (12.12%) were the most important. Leaf spot diseases, rosette and peanut bud necrosis (37.77%) and insects such as pod sucking bug and bruchid (27.77%) were considered to be the most important constraints limiting groundnut production. Among diseases, farmers in all the three regions indicated that late leaf spot is of economic importance which they associated to various causes such as maturity, drought, or insects. No gender differences were observed for the perception of constraints and groundnut traits preferences. Land size is significantly influenced by age and gender. Besides, farmers have pointed the lack of improved varieties and the unavailability of groundnut seeds highlighting the necessity of a sustainable groundnut seed system linked with a strong breeding program.
Conclusion
This study has enabled understanding of the farming practices, constraints, and farmers preferred characteristics, thus providing the basis for a participatory breeding program in Togo which should consider that farmers perceive low yielding varieties and diseases as major constraints to production
Screening of cowpea germplasm for resistance to Striga gesnerioides in Niger
The parasitic weed, Striga gesnerioides, is a major constraint to
cowpea production in sub-Saharan Africa. It causes significant yield
reductions of cowpea, especially in dry areas. The objective of this
study was to evaluate the response of 80 genotypes to Striga
gesnerioides under natural infestation. The results showed significant
variations in the resistance of cowpea lines to Striga; lines
IT93K-693-2, IT99K-573-1-1 and IT98K-205-8 being free from Striga
infestation; while lines 2491-171, 2472-154 and Suvita-2 supported few
Striga shoots. The other lines supported more and varied numbers of
emerged Striga shoots. The reduction of yield due to Striga infestation
was more pronounced for the susceptible genotypes as compared to the
resistant and tolerant lines. The high level of resistance observed in
some breeding lines can be exploited in breeding cowpea for resistance
to Striga. Principal Component Analysis (PCA) and clustering grouped
the genotypes in three main clusters as follow: (i) high yielding and
tolerant to Striga (ii) moderate yielding and resistant (iii)
low-yielding and susceptible.L\u2019herbe parasitaire, Striga gesnerioides est une contrainte
majeure de la production du ni\ue9b\ue9 en Afrique subsaharienne.
Elle cause des r\ue9ductions de rendement du ni\ue9b\ue9
tr\ue8s importantes dans les zones arides. Un criblage en vue
d\u2019\ue9valuer la r\ue9action de 80 g\ue9notypes sous
infestation naturelle du Striga a \ue9t\ue9 conduit au champ. Les
r\ue9sultats ont montr\ue9 qu\u2019il y a des diff\ue9rences
significatives dans la r\ue9sistance des lign\ue9es du
ni\ue9b\ue9 au Striga. Les lign\ue9es du ni\ue9b\ue9
IT93K-693-2, IT99K-573-1-1 et IT98K-205-8 \ue9taient indemnes de
pousses \ue9merg\ue9es du Striga tandis que les lign\ue9es
2491-171, 2472-154 et Suvita-2 ont support\ue9 peu de pousses
\ue9merg\ue9es du Striga. Les autres lign\ue9es ont support\ue9
des nombres vari\ue9s de pousses \ue9merg\ue9es du Striga.
L\u2019effet de l\u2019infestation du Striga a entrain\ue9 une
r\ue9duction du rendement des g\ue9notypes sensibles compar\ue9s
aux r\ue9sistants et aux tol\ue9rants. Le niveau \ue9lev\ue9 de
r\ue9sistance observ\ue9 chez certaines lign\ue9es peut \ueatre
exploit\ue9e dans l\u2019am\ue9lioration de la r\ue9sistance du
ni\ue9b\ue9 au Striga. L\u2019analyse du composant principal et la
hi\ue9rarchisation ont permis de grouper les g\ue9notypes en 3
principales grappes\ua0comme suit\ua0: (i) hautement productriceset
tol\ue9rantes au Striga (ii) moyennement productrices et
r\ue9sistantes (iii) faiblement productrices et sensibles
Genome-wide association study of root mealiness and other texture-associated traits in cassava
Open Access Journal; Published online: 17 Dec 2021Cassava breeders have made significant progress in developing new genotypes with improved agronomic characteristics such as improved root yield and resistance against biotic and abiotic stresses. However, these new and improved cassava (Manihot esculenta Crantz) varieties in cultivation in Nigeria have undergone little or no improvement in their culinary qualities; hence, there is a paucity of genetic information regarding the texture of boiled cassava, particularly with respect to its mealiness, the principal sensory quality attribute of boiled cassava roots. The current study aimed at identifying genomic regions and polymorphisms associated with natural variation for root mealiness and other texture-related attributes of boiled cassava roots, which includes fibre, adhesiveness (ADH), taste, aroma, colour, and firmness. We performed a genome-wide association (GWAS) analysis using phenotypic data from a panel of 142 accessions obtained from the National Root Crops Research Institute (NRCRI), Umudike, Nigeria, and a set of 59,792 high-quality single nucleotide polymorphisms (SNPs) distributed across the cassava genome. Through genome-wide association mapping, we identified 80 SNPs that were significantly associated with root mealiness, fibre, adhesiveness, taste, aroma, colour and firmness on chromosomes 1, 4, 5, 6, 10, 13, 17 and 18. We also identified relevant candidate genes that are co-located with peak SNPs linked to these traits in M. esculenta. A survey of the cassava reference genome v6.1 positioned the SNPs on chromosome 13 in the vicinity of Manes.13G026900, a gene recognized as being responsible for cell adhesion and for the mealiness or crispness of vegetables and fruits, and also known to play an important role in cooked potato texture. This study provides the first insights into understanding the underlying genetic basis of boiled cassava root texture. After validation, the markers and candidate genes identified in this novel work could provide important genomic resources for use in marker-assisted selection (MAS) and genomic selection (GS) to accelerate genetic improvement of root mealiness and other culinary qualities in cassava breeding programmes in West Africa, especially in Nigeria, where the consumption of boiled and pounded cassava is low
Introgression of drought tolerance traits into adapted Kenyan chickpea varieties using marker assisted backcrossing (MABC)
Drought is the major constraint causing considerable yield
reduction in chickpea. Roots play a critical role in enhancing
drought tolerance. The main objective of the study was to introgress
drought tolerant root traits into Kenyan chickpea varieties
through marker assisted breeding (MABC). Eight simple
sequence repeat (SSR) markers, linked to quantitative trait loci
(QTL) for root and yield traits, were used to screen the parents
at ICRISAT, India. In addition, 1144 single nucleotide polymorphic
markers (SNPs) were also used in genotyping these
parents at Legume Genomics Center, United Kingdom. Crosses
were made between two selected varieties, ICCV 92944 (Chania
Desi II) and ICCV 00108 (LDT 068) and ‘QTL-hotspot’ donor
parent ICC 4958 that has extensive rooting system. Polymor-
In the face of increasing water scarcity, breeding for higher transpiration
efficiency (TE), that is, the biomass produced per unit
of water transpired, has become crucial. This could be achieved
by reducing plant transpiration through a better closure of the
stomatal pores at the leaf surface. However, this strategy generally
also lowers growth, as stomatal opening is necessary for
the capture of atmospheric CO2 that feeds daytime photosynthesis.
Here, we considered the reduction in transpiration rate
at night (En), when photosynthesis is inactive, as a possible
strategy to limit water use without altering growth. We carried
out a genetic analysis for En and TE in grapevine, a major crop
in drought-prone areas. A 3 year experiment was conducted on
the F1 progeny from a cross between Syrah and Grenache cultiphic
SSR and SNP markers were used to select progenies with
root QTL at F1, BC1F1 and BC2F1 that were later advanced to
BC2F3. The BC2F3 populations were evaluated for root traits
at Egerton University in randomized complete block design
with two replications in pot experiment. The BC2F3 families
were significantly different for root dry weight (RDW), shoot
dry weight (SDW), total plant dry weight (PDW) and root to
shoot dry weight (R/S) ratio (R/S) for Chania Desi II x ICC 4958
and R/S for LDT 068 x ICC 4958. These lineshad significantly
improved root traits compared the recurrent parents. MABC
is aneffective and efficient method of introgressing complex
drought tolerant traits which leads to improvement in yield especially
under drought conditions
Reviewing the material and metal security of low-carbon energy transitions
The global transition to a low-carbon economy will involve changes in material markets and supply chains on a hitherto unknown scale and scope. With these changes come numerous challenges and opportunities related to supply chain security and sustainability. To help support decision-making as well as future research, this study employs a problem-oriented perspective while reviewing academic publications, technical reports, legal documents, and published industry data to highlight the increasingly interconnected nature of material needs and geopolitical change. The paper considers a broad set of issues including technologies, material supplies, investment strategies, communal concerns, innovations, modeling considerations, and policy trends to help contextualize policy decisions and regulatory responses. Policy options are outlined for each topical section, as well as areas for further research. Together, these recommendations serve to help guide the complex, interdisciplinary approach to materials required for a low-carbon transition
Genome-wide association mapping and genomic prediction for CBSD resistance in Manihot esculenta
Open Access Journal; Published online: 24 Jan 2018Cassava (Manihot esculenta Crantz) is an important security crop that faces severe yield loses due to cassava brown streak disease (CBSD). Motivated by the slow progress of conventional breeding, genetic improvement of cassava is undergoing rapid change due to the implementation of quantitative trait loci mapping, Genome-wide association mapping (GWAS), and genomic selection (GS). In this study, two breeding panels were genotyped for SNP markers using genotyping by sequencing and phenotyped for foliar and CBSD root symptoms at five locations in Uganda. Our GWAS study found two regions associated to CBSD, one on chromosome 4 which co-localizes with a Manihot glaziovii introgression segment and one on chromosome 11, which contains a cluster of nucleotide-binding site-leucine-rich repeat (NBS-LRR) genes. We evaluated the potential of GS to improve CBSD resistance by assessing the accuracy of seven prediction models. Predictive accuracy values varied between CBSD foliar severity traits at 3 months after planting (MAP) (0.27–0.32), 6 MAP (0.40–0.42) and root severity (0.31–0.42). For all traits, Random Forest and reproducing kernel Hilbert spaces regression showed the highest predictive accuracies. Our results provide an insight into the genetics of CBSD resistance to guide CBSD marker-assisted breeding and highlight the potential of GS to improve cassava breeding