Technical Report: Market opportunities and value chain analysis of fresh cassava roots in Uganda.

European UnionInternational Fund for Agricultural Developmen

CASSAVA BROWN STREAK DISEASE EFFECTS ON LEAF METABOLITES AND PIGMENT ACCUMULATION

Cassava Brown Streak Disease (CBSD) is a threat to productivity and product quality in East Africa. The objective of this study was to understand the effect of CBSD on the primary photosynthetic apparatus of cassava ( Manihot esculenta Crantz). Three cassava varieties with varying levels of reaction to infection by CBSD were chosen and subjected to field disease pressure. Disease progression and the resulting effects on leaf morphology, metabolite and pigment accumulation were assessed over a period of five months, beginning from 3 months after planting. Slight increments in leaf dry matter were observed up to 4 MAP, and there after a drop was registered. A significant (P<0.05) reduction in photosynthetic pigments occured with a fall in the Chla:Chlb and Chla:Carotenoid ratio, indicative of specific reductions in chlorophyll a (-80%) compared to Chlorophyll b (-41 to -62%) and Carotenoid (-11 to -18%). Total reducing sugar and starch content also dropped significantly (-30 and -60%, respectively), much as NASE 14 maintained a relatively higher amount of carbohydrates. Leaf protein levels were significantly reduced at a rate of 0.07 ug g-1 leaf per month in diseased treatments. Significant reductions in primary metabolites show altered leaf photosynthetic and growth metabolism, resulting into a compromised plant system that cannot perform optimally.La Maladie Stri\ue9e Brune du Manioc (CBSD) constitue une menace pour la productivit\ue9 et la qualit\ue9 des produits du manioc en Afrique de l\u2019Est. L\u2019objectif de cette \ue9tude \ue9tait de comprendre l\u2019effet de CBSD sur l\u2019appareil photosynth\ue9tique primaire du manioc ( Manihot esculenta Crantz). Trois vari\ue9t\ue9s de manioc poss\ue9dant differents niveaux de r\ue9sistance \ue0 CBSD ont \ue9t\ue9 soumises \ue0 la pression dans les conditions de plein champs. La progression de la maladie et son effet sur la morphologie foliaire, les metabolites et accumulations de pigments ont \ue9t\ue9 \ue9valu\ue9s sur une p\ue9riode de cinq mois, \ue0 compter du troisi\ue8me mois apr\ue8s semis. Il a \ue9t\ue9 observ\ue9e une l\ue9g\ue8re augmentation de mati\ue8re s\ue8che foliaire jusqu\u2019\ue0 4 MAP, suivie d\u2019une chute. Une r\ue9duction significative (P<0,05) des pigments photosynth\ue9tiques a \ue9t\ue9 observ\ue9e avec une chute dans le Chla:Chlb et Chla:ratio de Carotenoide, indiquant des r\ue9ductions sp\ue9cifique sen chlorophyllea (-80%) en comparaison avec la Chlorophylleb (-41 \ue0 -62%) et les Carotenoides (-11 \ue0 -18%). La r\ue9duction du sucre et d\u2019amidona connu aussi une diminution significative (-30 et -60%, respectivement), de m\ueame NASE 14 a maintenuun equantit\ue9 relativement\ue9 lev\ue9e d\u2019hydrates de carbone. Les niveaux de proteines foliaires \ue9taient significativement r\ue9duits \ue0 0,07 ug g-1 de feuille malade par mois. Des r\ue9ductions significatives des metabolites primaires sont \ue0 l\u2019origne de l\u2019alt\ue9ration du m\ue9tabolisme photosynth\ue9tique et de croissance, resultant \ue0 cycle v\ue9g\ue9tatif compromis qui ne peut permettre un d\ue9veloppement optimal de la plante

Effectiveness of pruning and waxing in reducing postharvest physiological deterioration in Uganda local cassava varieties.

Cassava ( Manihot esculenta Crantz) roots in the fresh form, are susceptible to postharvest physiological deterioration (PPD), thus reducing their economic value and farmer benefits. The objective of this study was to evaluate the effectiveness of pruning and waxing on fresh root storability among cassava varieties in Uganda. Sixteen cassava plants per variety (TME 14, NASE 14, Nyaraboke, Kirimumpale, and Bukalasa) were pruned seven days before harvest, leaving the rest as unpruned controls. After harvest, roots were divided into two portions and one portion was waxed using food grade wax. Pruning alone reduced PPD of stored roots by 23% at day 14 of storage; and by 19% at day 28 compared with the control. Pruning as a treatment resulted into increased sugar content, ranging 9-30%), and significant (P<0.05) losses in starch yield. Pruning combined with waxing, resulted in a reduction of up to 43% in PPD by day 14, and up to 67 at day 28. Reduction in carbohydrate (starch) was not significant (P>0.05) under the pruning and waxing treatment, which had minor effects on stored root composition. The results indicate that pruning is appropriate for the short-term storage of fresh cassava roots for up to 14 days. Waxing, combined with pruning, is suitable for longer term storage up to 28 days under Uganda conditions.Les racines de manioc ( Manihot esculenta Crantz) \ue0 l\u2019\ue9tat frais sont sensibles \ue0 la d\ue9t\ue9rioration physiologique apr\ue8s la r\ue9colte, r\ue9duisant ainsi leur valeur \ue9conomique et les avantages pour les agriculteurs. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer l\u2019efficacit\ue9 d\u2018 \ue9laguer et de cirer sur la capacit\ue9 de stockage des racines fra\ueeches parmi les vari\ue9t\ue9s de manioc en Ouganda. Seize plants de manioc par vari\ue9t\ue9 (TME 14, NASE 14, Nyaraboke, Kirimumpale et Bukalasa) ont \ue9t\ue9 \ue9lagu\ue9s sept jours avant la r\ue9colte, les autres \ue9tant des t\ue9moins non \ue9lagu\ue9s. Apr\ue8s la r\ue9colte, les racines ont \ue9t\ue9 divis\ue9es en deux parties et une partie a \ue9t\ue9 cir\ue9e avec de la cire de qualit\ue9 alimentaire. L\u2019\ue9lagage seul r\ue9duisait la PPD des racines stock\ue9es de 23% au 14e jour de stockage; et de 19% au 28e jour compar\ue9 au t\ue9moin. L\u2019\ue9lagage en tant que traitement a entra\ueen\ue9 une augmentation de la teneur en sucre (comprise entre 9 et 30%) et une perte significative (P <0,05) du rendement en amidon. La combinaison d\u2018 \ue9laguer et de cirer a entra\ueen\ue9 une r\ue9duction de la PPD de 43% au 14e jour et de 67 ans au 28e jour. La r\ue9duction de la teneur en glucides (amidon) n\u2019\ue9tait pas significative (P> 0,05) dans le cadre des traitements d\u2018 \ue9laguer et de cirer a eu des effets mineurs sur la composition des racines stock\ue9es. Les r\ue9sultats indiquent que l\u2018\ue9laguage convient au stockage \ue0 court terme de racines de manioc fra\ueeches pendant 14 jours au maximum. La combinaison d\u2018 \ue9laguer et de cirer convient au stockage \ue0 long terme jusqu\u2019\ue0 28 jours dans les conditions ougandaises