Cassava is considered the most important crop in the tropics in terms of its high yield, its potential to produce large amounts of calories in food and income to producers. In Central and East Africa, from 2000 to 2010, the African mosaic no longer constituted a major constraint to culture for research because researchers from national and international institutions mobilized to fight the pandemic by developing no varieties resistant to this cassava virus. Unfortunately, the period following the year 2010, the culture experienced a qualitative and quantitative depreciation of the tuberous roots in most producing regions. All the varieties selected for mosaic resistance are ravaged by the brown streak disease which extends from East to Central Africa without sparing the East of the Democratic Republic of Congo with its varieties selected and distributed by the Centers INERA research centers such as Liyayi (MM 96/0287), Mayombe (MM 96/7752), Sawasawa (MM 96/3920), Obama 1 (TME 419). As part of the fight against the disease, the presence of which has been confirmed in the East since 2012, we have set up a participatory variety selection trial in two sites, in particular in the Mulungu Research Station and in the Ruzizi plain, where disease pressure is greatest. The objective of the trial was to identify at least one material tolerant or resistant to brown streak after evaluation of a few clones having passed the stage of the uniform yield trial. Three repetitions are installed in the two sites with 5 materials and 2 improved controls, one of which is tolerant and the other sensitive to the disease. Cuttings taken from apparently healthy plants are planted at 1mx1m spacing. After 12 months of vegetation, the trial is harvested and several materials have proven to be efficient to different degrees. Only clone MLG 2011/092 showed no brown streak symptoms on leaves and roots. Its average yield of 36.661 t/ha is far above the average yield of the trial (34.830 t/ha) on the one hand; and that of the improved control Nabana (32.708 t/ha) which is currently the most cultivated variety for its tolerance to the disease in the most affected area. The MLG 2010/180 clone also seems interesting because of its highest yield of all the others (52.598 t/ha), the low average severity of attack on the leaves (2.8) and in the roots (2.55); the average incidence of the disease in the roots is also less than 25%.

Cassava is the main food crop grown in all provinces of the Democratic Republic of Congo. Increasing its productivity therefore comes up against multiple constraints, including diseases, in particular the endemic form of the mosaic, which occupies a prominent place. Small farmers who are the main producers remain much attached to local varieties although research regularly develops and disseminates improved varieties resistant to the African cassava mosaic. The objective of the study we conducted was, on the one hand, to assess the real yields of the resistant varieties disseminated and of the most widely cultivated local variety and, on the other hand, to determine the rate of loss of production of the variety. Local compared to varieties improved in distribution. The trial, set up with the active participation of the peasantry, included 4 repetitions in 4 different sites, near the peasants' fields. Four treatments consist of 4 varieties including 3 improved and 1 local. Cuttings taken from plants without disease symptoms are planted at 1mx1m spacing’s and harvesting took place 12 months after planting. The recovery was observed 1 month after planting, while data on diseases and pests are taken from the third month of planting until harvest at 3-month intervals. The results obtained show that the severity and incidence of the mosaic were higher on the local variety than on the improved varieties, one of which was shown to be somewhat susceptible to the disease. The loss of production of the local variety is estimated at plus or minus 50% compared to the average yield of the improved varieties.