Impact of Altitude on Morphological Traits-based Phenotypic Variability in Bidens pilosa L. from Three Natural Regions of Burundi

Aims: To examine the possible influence of varying altitudes on the morphological traits-based phenotypic variability in Bidens pilosa L.

Study Design: Randomly selected plants from each natural region.

Place and Duration of Study: Three natural regions of Burundi, i.e. IMBO (842 m), KIRIMIRO (1645 m), and MUGAMBA (2075 m), between November 2015 and May 2016.

Methodology: We randomly selected 36 plants (12 plants from each of the three sites of seed sowing and plant development) for which we measured plant life cycle stages such as the period of germination, the period of leaf formation, flowering period, fruit formation period and complete maturity period. Plant height, internode length, leaf length, leaf width, inflorescence length, achene length, inflorescence number, node number, achene number per inflorescence and achene number per plant, after plant complete maturity were also recorded. Obtained data were statistically analyzed.

Results: Bidens pilosa from IMBO (842 m) showed the lowest periods of germination, leaf formation, flowering, fruit formation and complete maturity, while longest periods were observed in MUGAMBA (2075 m) region. In addition, one-way analysis of variance showed that phenotypic variation in Bidens pilosa was highly significant within and across populations (P = 0.000) for the studied quantitative morphological traits except the achene number/inflorescence (P = .887). Some traits increased with increase in altitude while others decreased with increase in altitude. Moreover, internode length, leaf length, inflorescence number and achene number per plant significantly differentiated the three populations from the three regions (P < 0.01). Cluster analysis revealed also that IMBO (842 m) population was different from KIRIMIRO (1645 m) and MUGAMBA (2075 m) which are tending to be closer.

Conclusion: Altitudes significantly influenced phenotypic variability of Bidens pilosa. However, further studies on a wide range of morphological traits and altitudes are needed as well as biochemical and molecular analyses.