Response of potato genotypes to production sites and water deficit imposed at different growth stages.
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Date
2020
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Abstract
In South Africa, potato is an important food security crop widely cultivated by smallholder
farmers due to its extensive adaptation characteristics. However, drought adaptive responses
of potato genotypes vary under different environmental conditions. Potato is generally
categorized as the most sensitive crop to water deficit than other root and tuber crops.
However, there is insufficient evidence regarding adaptive responses of potato genotypes to
water deficit imposed at different growth stages. Therefore, this study sought to identify
growth stage-specific drought adaptation of selected potato genotypes for recommendation
and cultivation in targeted production sites in South Africa. The specific objectives of this
study were: (1) to determine morpho-physiological traits related to water use efficiency
among selected potato genotypes subjected to water deficit at the different growth stages; (2)
to determine the effect of water deficit imposed at different growth stages on yield
performance and tuber quality of selected potato genotypes; and (3) to investigate the effect
of different production sites/regions on growth, physiological and yield responses of potato
genotypes.
For objective 1, a glasshouse study was conducted using a 8×4×2 factorial experiment
involving the following factors: potato genotypes - 8 levels (Bikini, Challenger, Electra,
Mondial, Panamera, Sababa, Sifra, and Tyson); growth stages - 4 level (vegetative stage,
tuber initiation, tuber bulking and maturity) and watering regimes - 2 levels (Well-watered
[Ww] and Water deficit [Wd] conditions). The treatments were replicated three times to give
a total of 192 experimental units. Water deficit was imposed by withholding irrigation at the
beginning to the end of each growth stage. A highly significant (p < 0.001) interaction among
genotypes, water condition and growth stages was observed for morphological traits and
physiological responses including number of leaves and total above-ground biomass, and
photosynthetic rate (A), instantaneous water use efficiency (IWUE), transpiration rate (Tr),
chlorophyll content index (CCI), and relative water content (RWC). Potato genotypes Bikini,
Challenger and Mondial with growth-stage specific drought adaptation were identified and
recommended for water-limited environments.
The second study (objective 2) determined the effect of water deficit imposed at different
growth stages on yield performance and tuber quality of selected potato genotypes. The study
was conducted as 8×4×2 factorial experiment (See objective 1) replicated three times and
data was collected on tuber yield (TY), number of tubers (NT), tuber size distribution (TSD)
and dry matter content (DMC). Results revealed a highly significant (p < 0.001) genotype x
water condition x growth stages interaction for tuber yield and dry matter content. Imposing
water deficit at the tuber initiation and tuber bulking stages resulted in significantly lower
yields, whereas drought stress at maturity stage resulted in high number of small tubers.
‘Bikini’, ‘Challenger’, ‘Mondial’ and ‘Tyson’ were identified as tolerance genotypes to water
deficit at vegetative stage, tuber initiation and maturity stage due to high yield potential and
DMC. This finding suggests that these genotypes could be suitable for processing industry
(chipping) and baking.
For objective 3, eight potato genotypes were grown across two environments namely:
Ukulinga research farm (URF) in Pietermaritzburg which characterised with semi-arid
environment and eChibini area (CB) in Bamshela with seasonal rainfall and high humidity.
The experiments were laid out using a randomised complete block design (RCBD) replicated
three times. Data was collected on morphological and physiological traits. Significant (p <
0.05) genotype x environment interaction effect was observed for studied traits at URF and
CB. Potato genotypes planted at CB had a significant (p < 0.05) lower gs and Tr resulting to
low A, than at URF. The CCI at CB compared to URF was significant (p < 0.05) higher at the
beginning and gradually decreased towards maturity while at URF was constant. Moderately
to poorly drained soils at eChibini resulted in low yields and low dry matter content. Various
genotypes with better yield and high quality were obtained at URF. This suggested that
genotypes were suitable for production in cool temperate regions with humid climate areas
like URF. The study showed that different production regions can significantly affect the
potato yield performance, suggesting URF sites as suitable environment.
Overall, the study identified potato genotypes with growth stage-specific drought tolerance
and environment specific adaptation for high yield and good quality.
Description
Masters Degree. University of KwaZulu-Natal, Pietermaritzburg.