Cassava mosaic disease (CMD) threatens cassava (
Manihot esculenta
) production in Africa. A total of 24 selected cultivars were screened against CMD using combined molecular and greenhouse grafting tools. Disease severity was recorded for 10 weeks after inoculation and the molecular markers associated with
CMD2
were detected by PCR. CMD severity significantly differed (
P
< 0.0001) among cultivars. Twelve cultivars were morphologically resistant and eight of these possessed
CMD2
and four did not. These results suggest that there are several CMD-resistant cassava cultivars that could be recommended for on-farm production and for conservation and breeding programs.
Cassava production in Africa is constrained by cassava mosaic disease (CMD) that is caused by the Cassava mosaic virus (CMV). The aim of this study was to evaluate the responses of a range of commonly cultivated West African cassava cultivars to varying inoculum doses of African cassava mosaic virus (ACMV). We grafted 10 cultivars of cassava plants with different inoculum doses of CMV (namely two, four, or six CMD-infected buds) when the experimental plants were 8, 10, or 12 weeks old, using non-inoculated plants as controls. Three cultivars showed disease symptoms when grafted with two buds, and four cultivars showed disease symptoms when grafted with four or six buds. Most cultivars became symptomatic six weeks after inoculation, but one (‘TMS92/0326’) was symptomatic two weeks after inoculation, and two (‘Ntollo’ and ‘Excel’) were symptomatic after four weeks. Root weight tended to be lower in the six-bud than in the two-bud dose, and disease severity varied with plant age at inoculation. These results indicate that the level of CMD resistance in cassava cultivars varies with inoculum dose and timing of infection. This will allow appropriate cultivars to be deployed in each production zone of Africa in accordance with the prevalence of CMD.
The oil palm (Elaeis guineensis Jacq.) is cultivated mainly for crude palm oil (CPO) which is extracted from the mesocarp of fruits. The quality of CPO is generally impaired due to high acidity, as a result of the activity of a lipase present in the mesocarp of the fruits at maturity. The objective of this study was to establish the genetic determinism of "palm oil acidity" (POA) from E. guineensis. Acidity was analyzed on CPO from the mesocarp of ripe fruits of some DELI parent palms used for the production of commercial seeds at CEREPAH Dibamba. Acidity analysis of 457 individuals from 11 progenies, issued from nine parents showed that, the segregation of forms with respect to this trait is compatible with a monohybridism with dominance. The dominant allele denoted that "Pa" determines high acidity while the recessive allele "pa" favours production of oil with low acidity.
This work aims to study the development of the pericarp of the fruit of Elaeis guineensis Jacq. var. dura. The thickness, the water and the oil contents of its tissues are evaluated every two weeks, from pollination to the maturity of the fruit. The development of the oil palm fruit takes 5.5 months. The endocarp reaches its maximum thickness at the 70th DPP (day post-pollination), with a water content of 72%. It then starts its dehydration, while sclerifying. It therefore isolates the seed at start and later protects it. The mesocarp is visible at anthesis and its water content is close to 92%. From the 100th DPP, it begins a continuous dehydration associated, from the 130th DPP, with an active lipids biosynthesis. Ultimately, the pericarp of the oil palm fruit fulfills both functions, namely to protect the seed by early sclerification of the endocarp and ensure the dissemination of the species by the high oil content of the mesocarp. A comparative anatomy of the pericarp tissues of the three genotypes of E. guineensis Jacq., during the first three weeks of fruit development, will enhance the understanding of the primary effect of sh gene.
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