Relationship between environmental temperature and rainfall on beta carotene content and yield in selected sweet potato (Ipomoea batatas (L.) Lam.) varieties
Date
2016
Authors
Singogo, Brian
Journal Title
Journal ISSN
Volume Title
Publisher
University of Zambia
Abstract
Sweetpotato (Ipomea batatas (L.) Lam) is becoming one of the most important tuber crops in Zambia
and ranks second in importance from cassava. Orange fleshed varieties are being introduced to reduce
vitamin A deficiency. However, the expression of β-carotene content, dry matter content and tuber
yield among these varieties under different environmental conditions is not known. This study was
conducted to establish the relationship between environmental temperature and rainfall on β-carotene
content and yield of four orange fleshed sweetpotato varieties namely; Orange Chingovwa, Olympia,
Kokota and Zambezi. The study was conducted in the Eastern province of Zambia at three sites with
different climatic conditions. Sites were categorised into high temperature site (HTS) (38.5 oC),
moderate temperature site 1 (MTS1) (32.2 oC) and moderate temperature site 2 (MTS2) (31.2 oC).
Average rainfall for the 3 sites was 341 mm, 647 mm and 520 mm, respectively during the 2013/2014
growing season. Results showed that environment significantly influenced β-carotene content. HTS
showed lower β-carotene contents than the 2 MTS. HTS showed 7.23mg/100g whereas MTS recorded
MTS1 (15.56mg/100g) and MTS2 (15.46mg/100g). Among varieties, Zambezi and Orange
Chingovwa were best performers for β-carotene content across all sites at 21.21mg/100g followed and
(18.85mg/100g), respectively. Kokota was least performing genotype (3.28mg/100g) followed by
Olympia (7.65mg/100g). β-carotene differed within genotypes and across production environments.
Results indicated that β-carotene increased with warm temperatures and declined with hot
temperatures. HTS showed lower yields (0.97 t/ha) than the two moderate temperature sites. The two
moderate temperature sites had similar root yield results of 11.96 and 9.41 t/ha. Genotype Olympia
consistently produced highest root yield across sites 12.2 t/ha followed by Kokota (7.6 t/ha) while
Zambezi and Orange Chingovwa had 3.6 and 6.4 t/ha. Vine Yield (VY) was highly significantly
different for sites at p < 0.001. HTS showed highest VY (23.6 t/ha) while the two MTS had lowest VY
of (8.7 and 12.9 t/ha). Leaf area (LA) was significantly different for sites, varieties and their
interactions. Significant interactions were recorded under different environments for Orange
Chingovwa and Olympia. Genotype Kokota and Zambezi had consistently high mean LA across all
sites. HTS exhibited high leaf development, high LA, high VY with low tuber development, low β-
carotene, and low root yield as compared to the other two MTS. However further research to further
quantify these relations particularly under controlled temperature regimes are necessary and
sweetpotato breeders should be breeding genotypes ideal for specific environments for enhanced yield
and β-carotene content in sweetpotato roots.
Description
Master of Science in Agronomy
Keywords
Sweet potatoes--Research. , Food crops--Breeding