Canopy Structure and Photosynthetic Performance of Irrigated Cassava Genotypes Growing in Different Seasons in a Tropical Savanna Climate

Supranee Santanoo,Piyada Theerakulpisut,Sanun Jogloy,Kochaphan Vongcharoen,Poramate Banterng,Nimitr Vorasoot,Sittiruk Roytrakul

doi:10.3390/agronomy10122018

Abstract

Growth and photosynthesis performance of cassava during early vegetative growth are important determinants of final biomass. The objective of this work was to investigate canopy structure and photosynthesis performance of four cassava genotypes (Rayong 9, Rayong 11, Kasetsart 50, and CMR38-125-77) growing under irrigation at 3 and 6 months after planting (3MAP and 6MAP). Data for the 3MAP plants were collected from cassava planted on 30 June (Rainy PD), 10 November (Cool PD1), and 15 December (Cool PD2) 2015; and for the 6MAP from those planted on 20 April 2015 (Hot PD), Rainy PD, and Cool PD1. The plants growing in the rainy season had significantly higher leaf area index (LAI) than those growing in the cool and hot seasons. Consequently, they had lower percentage light penetration at the bottom of canopy, and therefore more light interception through the canopy, and hence a higher mean net photosynthesis rate (Pn) across the six canopy levels. At the 3MAP, which is the stage of maximum rate of leaf and stem growth, the Rainy PD and Cool PD2 plants of CMR38-125-77 showed the highest LAI and highest mean Pn. Similarly, the Cool PD1 plants of Kasetsart 50 showed the highest LAI and highest mean Pn. In contrast, at 6MAP during the stage of active starch accumulation in storage roots, the genotypes with the highest mean Pn were the ones having an intermediate (CMR38-125-77 for the Hot PD) or low LAI (Rayong 9 for the Rainy PD, and CMR38-125-77 for the Cool PD1). Data on variations in canopy structure and photosynthesis potentials of different cassava genotypes in response to seasonal variations may be useful for crop growth modeling and may be employed as a criterion for the selection of suitable genotypes for each growing season.

Highlights

Cassava (Manihot esculenta Crantz) has great potential for enhancing food security and utilization in the future under global climate change because of its ability to tolerate dry conditions and recover from biotic and abiotic stress [1,2]
The environmental conditions in the rainy season were more favorable for early development of cassava (30 June to 30 September 2015; the Rainy planting dates (PD)) than those in the cool season
Causing the rainy-season plants at 3MAP to have significantly higher leaf area index (LAI), leading to lowest light penetration through the bottom of canopy, and more light being absorbed by upper canopy layers resulting in higher mean photosynthesis rate (Pn) across six canopy levels, and higher photosynthetic capacity

Summary

Introduction

Cassava (Manihot esculenta Crantz) has great potential for enhancing food security and utilization in the future under global climate change because of its ability to tolerate dry conditions and recover from biotic and abiotic stress [1,2]. The storage roots of cassava can be harvested from 8 to 18 months after planting (MAP), depending on cultivars and growing conditions [4]. Cassava is flexible as to the time of harvest and can be stored naturally for long periods by keeping the plants in the field with the roots in the soil [5]. Tuberous roots of cassava have high starch content of. Primary products of cassava in the forms of chips and pellets can be further processed into high value-added starch derivative products, such as paper, textile, plywood, glue, beverages, and ethanol [9]

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