Morphological Traits as Indicators of Bitterness in Traditional Vegetables: The Case of Spider Plant (Gynandropsis gynandra) in Kenya

Abstract

Aims: The study set out to find the existence of variation in leaf bitterness of spider plant (Gynandropsis gynandra) in six (6) agro-ecological zones in Kenya and whether levels of leaf bitterness correlated with morphological characters; colour of main stem including colour of leaf blade, stem pubescence and leaf waxiness.

Study Design: Morphological characterization was done using purposive sampling method while organoleptic characterization was done using a ‘within participants’ method.

Place and Duration of Study: Coast, Eastern, Central, Rift Valley and Nyanza regions of Kenya representing agro-ecological zones; upper highlands, lower highlands, upper midlands, lower midlands, inland lowlands and coastal lowlands, sampled between 2016-2017.

Methodology: Morphological characterization for Gynandropsis gynandra was done using IPGRI descriptors in 18 sites selected on the basis of agro-ecological zones. Mature healthy seeds of spider plant were collected from the accessions characterized and grown at Nairobi Botanic Garden using a randomized block design. Organoleptic testing was done on 40 spider plant accessions which grew to maturity. Qualitative analysis performed on four (4) qualitative traits; colour of main stem, stem pubescence, leaf waxiness and colour of leaf blade was correlated to levels of bitterness using Pearson correlational analysis. Leaf bitterness and colour of leaf blade showed significant variation in six agro-ecological zones. Leaf bitterness levels were high in coastal lowlands and lower midlands and low in highlands. Colour of leaf blade strongly associated with leaf bitterness while others correlated weakly. Gynandropsis gynandra specimens were grouped into two (2) main clusters which were further divided into eight (8) clusters in the dendogram based on level of leaf bitterness.

Changes in agro-ecology had a significant effect on the level of bitterness while the colour of the leaf blade was a strong indicator of the level of leaf bitterness of spider plant. The colour of leaf blade was recommended for distinguishing non-bitter types from bitter types of spider plant.