Cassava brown streak disease effects on leaf metabolites and pigment accumulation

E Nuwamanya,C.A Omongo,P Abidrabo,E Atwijukire,T Alicai,S Acheng,Y Baguma

doi:10.4314/acsj.v25i1.3

E Nuwamanya, C.A Omongo + Show 5 more

Open Access

https://doi.org/10.4314/acsj.v25i1.3

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Abstract

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.Keywords: Carotenoid, leaf metabolites, photosynthesis, protein

Highlights

Cassava (Manihot esculenta Crantz) is a main food crop in Sub-Saharan Africa (SSA), Asia and Latin America, for more than 280 million inhabitants
The disease (CBSD) has a significant effect on leaf morphology, with observable browning of leaves (Mbanzibwa et al, 2009)
No significant variety differences were observed for dry matter, a higher value was observed for NASE 14 throughout the disease period

Summary

Introduction

Cassava (Manihot esculenta Crantz) is a main food crop in Sub-Saharan Africa (SSA), Asia and Latin America, for more than 280 million inhabitants. Cassava brown streak disease (CBSD) is one of the most devastating diseases (Pennisi, 2010), difficult to identify and manage; resulting in almost 100% yield losses (Ogwok et al, 2012). The disease (CBSD) has a significant effect on leaf morphology, with observable browning of leaves (Mbanzibwa et al, 2009). The symptoms depend on the age of the plant and the weather; making it difficult to differentiate the resultant effects. The symptoms show a general yellowing, pointing to loss of green pigmentation in the leaves; and it is postulated that there is a general effect of the disease on photosynthesis (Alicai et al, 2007; Mbazibwa et al, 2009; Ogwok et al, 2012). The loss in yield is evident, much as the loss in root dry matter content is not obvious (Nuwamanya et al, 2015)

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