Abstract
The prevalence of vitamin A deficiency in sub-Saharan Africa necessitates effective approaches to improve provitamin A content of major staple crops. Cassava holds much promise for food security in sub-Saharan Africa, but a negative correlation between β-carotene, a provitamin A carotenoid, and dry matter content has been reported, which poses a challenge to cassava biofortification by conventional breeding. To identify suitable material for genetic transformation in tissue culture with the overall aim to increase β-carotene and maintain starch content as well as better understand carotenoid composition, root and leaf tissues from thirteen field-grown cassava landraces were analyzed for agronomic traits, carotenoid, chlorophyll, and starch content. The expression of five genes related to carotenoid biosynthesis were determined in selected landraces. Analysis revealed a weak negative correlation between starch and β-carotene content, whereas there was a strong positive correlation between root yield and many carotenoids including β-carotene. Carotenoid synthesis genes were expressed in both white and yellow cassava roots, but phytoene synthase 2 (PSY2), lycopene-ε-cyclase (LCYε), and β-carotenoid hydroxylase (CHYβ) expression were generally higher in yellow roots. This study identified lines with reasonably high content of starch and β-carotene that could be candidates for biofortification by further breeding or plant biotechnological means.
Highlights
Cassava (Manihot esculenta Crantz) is an important starchy root crop in the tropics
This proves that some yellow root cultivars can be an adequate source of both starch and provitamin A carotenoids, and partly contradicts the generally reported negative correlation between Dry Matter Content (DMC) and total carotenoid content in cassava storage roots [13]
Several studies observed a negative correlation between carotenoid content and dry matter content in African cassava germplasm
Summary
Cassava (Manihot esculenta Crantz) is an important starchy root crop in the tropics. It is a common staple food in Africa, Asia, and Latin America [1], and of high importance in sub-SaharanAfrican countries. Cassava (Manihot esculenta Crantz) is an important starchy root crop in the tropics. It is a common staple food in Africa, Asia, and Latin America [1], and of high importance in sub-Saharan. Cassava is cultivated for its tolerance to stress and ability to grow under drought conditions [2]. Cassava serves as an important component for food security for low income farmers who rely on it as a major source of dietary energy. While cassava is rich in starch and serves as a good energy source, it is extremely low in protein and important micronutrients, such as Agronomy 2020, 10, 424; doi:10.3390/agronomy10030424 www.mdpi.com/journal/agronomy. A diet reliant on cassava predisposes one to malnutrition, especially provitamin A deficiency
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