Phytosanitary situation of maize streak virus in the main maize production zones of Cameroon

Open Access Article; Published online: 09 Apr 2021Maize streak caused by the Maize streak virus (MSV, genus Mastrevirus) is transmitted by Cicadulina spp., and is responsible for considerable maize yield losses in all maize production zones in Africa, including Cameroon. A survey was conducted in 3 agro-ecological zones (AEZ) of Cameroon (Sudano-Sahelian: zone I, Western Highlands: zone III and Bimodal Rainforest: zone V) between November 2017 and November 2019 to determine the status of streak disease in maize farms. The incidence and severity were determined in 90 maize fields, 30 fields per AEZ; the effect of lightning on the disease was also assessed using 15 fields under shade and 15 opened fields per AEZ. The highest streak disease incidence (60%) was found in AEZ I, whereas the lowest incidence was 10% in AEZV. The highest disease incidence and severity (80% and 4.5 respectively) were observed in maize fields under shade as compared to open fields (70% and 4.5 respectively). The phylogenetic analysis of MSV sequences from symptomatic plants indicated it as MSV-A strain identical to be previously reported to determine the virus diversity in relation to the other characterization isolates. This information is important for the development of control strategies to limit yield losses due to MSV

Preliminary study on character associations, phenotypic and genotypic divergence for yield and related quantitative traits among cowpea landraces (Vigna unguiculata) from the Western Highland Region of Cameroon

Cowpea (Vigna unguiculata) is an important tropical legume crop contributing significantly to food security in tropical regions. The present study was carried out to determine the extent of genetic variation, to estimate character associations, heritability and genetic advance of 25 quantitative traits in 30 genotypes of cultivated Vigna unguiculata from the western highland region of Cameroon. These quantitative traits were selected among cowpea descriptor lists. For all these traits, the analysis of variance showed significant difference among genotypes, highlighting the existence of important genetic divergence among the studied accessions. The highest phenotypic and genotypic coefficient of variation was observed in grain yield, pod yield and 100 seed weight. Genetic advance of these three characters was also the highest. Broad sense heritability was high in general, with 20 traits out of 25 having heritability values greater than 70%. This high heritability indicates little influence of the environment on these characters in cowpea. The highest heritability was recorded for 100 seed weight (98.15%) and the lowest for shoot weight (41.38%). At 0.05 probability level, grain yield correlated significantly with 21 out of the 24 other quantitative traits. Among others, grain yield correlated positively and significantly with 100 seed weight, number of pods per plant, number of branches per plant, number of nodes per plant, plant height, plant width, pod length, pod width, seed length, seed width and number of seeds per pod. These positive correlations between grain yield and many other traits indicate that a selection program based on any of these traits will result in increasing yield. Cluster analysis using UPGMA method revealed five distinct clusters. Genotypes named KEB-CP025, KEB-CP006, KEB-CP098, KEB-CP070, and more importantly KEB-CP054 and KEB-CP004, were grouped in a single cluster and were characterized by a significantly higher grain yield, pod yield, number of pods per plant, number of seed per pod, plant height, pod length and pod width compared to other clusters. Accessions KEB-CP036 and KEB-CP031 produced significantly more important fresh biomass. These genotypes could be used as parents in genetic improvement programs aiming to increase yield and fresh biomass in cowpea

Ex Situ conservation of potato [Solanum Section Petota (Solanaceae)] genetic resources in genebanks.

Conserving the genetic diversity of potato is critical for the long-term future of potato improvement programs. Further, it is the social and ethical responsibility of the present generation to ensure future generations have the same opportunities to use, exploit, and benefit from the genetic diversity that exists today. Genebanks and the ex situ conservation of potato genetic resources are the only way to ensure this happens; in situ conservation plays a complementary role, but it can never ensure that the vast diversity that exists on earth today is still there for use in the future. Material in ex situ genebanks not only serve as a reservoir of ready-to-use genetic material when needed but also provide invaluable tools for research now and in the future of cultivated potato and its wild relatives