Nontimber Forest Product Yield and Income fromThaumatococcus danielliiunder a Mixed Tree Plantation System in Ghana

Abstract

Thaumatococcus daniellii is a wild sourced tropical understorey herb that is harvested for its foliage and fruits from which thaumatin-a proteinous sweetener-is extracted. With increased demand for natural sweeteners, uncontrolled harvesting of T. daniellii from the wild is suggested to be neither sustainable nor match industrial demands. This study determined the implication of controlled foliage harvesting of T. daniellii under a mixed indigenous tree plantation stand. T. daniellii plants within plots of dimension 3 m × 4 m were thinned to uniform foliage population of about 12 leaves/m 2 and subsequently harvested at 16 weeks interval for 64 weeks at four different foliage harvesting intensities: (i) no harvesting (control), (ii) 25% harvest, (iii) 50% harvest, and (iv) 75% harvest. Data on agronomic characters and total income from the sale of fruit and harvested foliage were collected and analysed. We found that foliage harvest intensity affected (P < 0.001) number of flowers in the order: 18 (control) > 6 (25%) ≥ 1 (50%) and 0 (75%). Foliage harvest intensity also significantly (P = 0.036) influenced fruit number and ranged from 11458/ha for the control to 4583/ha for the 75% harvest. Total income from fruit and foliage sales was greatest for the 50% harvest (US $ 17,191.32), followed by 75% harvest (US $ 12, 310.24) and lowest for the no harvest treatment (US $ 107.44). Thus, proper management of T. daniellii through controlled harvesting of the foliage under mixed tree plantation system could promote sustainable yield and income to farmers.

Thaumatococcus daniellii phenology and growing degree day requirements under different irradiance and fertiliser levels

“…Also, four stages were assigned to reproductive growth, which included inflorescence/synflorescence emergence (stage 5), flowering (stage 6), fruit development (stage 7) and fruit maturity (stage 8) (Table ). The harvestable vegetative part (stage 4) and senescence (stage 9) were not applicable to this species because under normal practice for achieving high yield, vegetative parts were not harvested (Boadi et al, ) while fruits were harvested during the fruit maturity stage similarly to other fruit crops (Hernández Delgado et al, ; Wei et al, ).…”

“…This soft textured light green leaf will unfold into a fully expanded hard textured green leaf. New tillers develop leaves and petioles that are larger and taller than the ones produced earlier (Waliszewski et al, ), and competes for irradiance in order to achieve maximum photosynthesis (Boadi, Baah‐Acheamfour, Ulzen‐Appiah, & Jamro, ). This is accomplished by specialised pulvinus that enables leaf lamina to track irradiance (Andersson, ).…”

“…It has been utilised as flavour modifier and food additive (E957) in food and drink products and considered safe for use by the European Union (Mortensen, ). Due to the high price tag on thaumatin (Boadi et al, ; Leong‐Škorničková, ), several transgenic plants with thaumatin genes were developed in crops (Akter, Huq, Jung, Cho, & Kang, ) such as cucumber (Szwacka, Krzymowska, Osuch, Kowalczyk, & Malepszy, ), strawberry (Schestibratov & Dolgov, ) and tomato (Bartoszewski, Niedziela, Szwacka, & Niemirowicz‐Szczytt, ) in order to meet the increasing demand.…”

“…Additionally, leaves and petioles are also used for food wrapping, roof thatching, mat weaving and pulp production (Arowosoge & Popoola, ; Sotannde & Oluwadare, ; Ogunsanwo, Adedeji, & Ajibabi, ). It was estimated that at the cottage industry level, the income from one‐hectare cultivation may reach up to USD 12,310 through various products of leaves, petioles and fruits (Boadi et al, ).…”

“…daniellii has aroused the interest of researchers and scientists in getting more information on various related aspects such as diversity (Waliszewski, Sinclair, & Steele, ), agronomic practices (Most et al, ; Waliszewski et al, ), biochemistry of thaumatin (Mackenzie, Pridham, & Saunders, ; Van Der Wel & Loeve, ) and economic importance of T . daniellii (Boadi et al, ; Oluwatayo & Ojo, ). However, a detailed phenological development that demonstrates the beginning and ending of various phenophases vis‐à‐vis thermal time has never been proposed for this species.…”