Ethnobotanical use, threat status and optimalenvironmental germination conditions for conservation of aloe species in Tanzania

Abstract

The genus Aloe is known for its use in healthcare and cosmetics. Many Aloe species are globally threatened due to over-harvesting for trade and habitat destruction. In Tanzania, over-exploitation threats some Aloe species with extinction, and yet little has been documented on the abundance, bio-cultural uses, threats, seed biology and appropriate conservation measures. Semi-structured questionnaires were used to obtain ethnobotanical information and perception of Aloe species' threat factors from 236 respondents in Kilimanjaro, Tanga, and Mara and Katavi-Rukwa regions. Geospatial Conservation Assessment software (GeoCAT) was used to assess the Area of Occupancy and Extent of Occurrence of Aloe species. The temperature, light, scarification, KNO3 and salinity among the Critically Endangered and the Least Concern Aloe species were tested to understand optimal environmental conditions for their optimal growth. For the Critically Endangered A. boscawenii, an ideal concentration for sterilization and rooting hormone were determined to promote tissue cultivations. A total of 23 Aloe species were identified, with A. secundiflora being the most widely used species. Malaria and general stomachache in humans, and Newcastle disease in chickens were frequently treated with Aloe species. Among the 22 Aloe species re-assessed, two were categorized as Critically Endangered, ten as Endangered, five as Vulnerable, one as Nearly Threatened and five as Least Concern. Aloe boscawenii was re discovered after not having been seen for more than six decades. The conservation status of the Aloe species endemic to Tanzania and previously categorized as Critically Endangered were upgradeed. All the tested Aloe species germinated best at moderate temperatures (25°C and 30°C) and low KNO3 levels (0.01 mg/L). The Critically Endangered A. boscawenii was successfully regenerated through tissue culture at 6% of NaOCl and rooted at NAA: IBA (2:1) concentration. The genus Aloe is widely used across Tanzania, as such 77% (N = 22) of Aloe species assessed in this study are threatened, mainly due to human activities. Hence, there is a need to formulate laws and policies to protect Aloe natural habitats. Moreover, the Aloe seeds exhibited species specific responses to various environmental conditions (except for A. pembana). Furthermore, tissue culture is an ideal conservation tool for the threatened species as it outperforms the traditional methods.