Morphological diversity in purple nutsedge from four agro-ecological zones in Ghana.

Purple nutsedge (Cyperus rotundus L.) exhibits plasticity and are morphologically different under different conditions. Due to these differences, the weed might respond differently to weed management. Here, we examined the morphological characteristics of purple nutsedge from southern Ghana relative to those reported from other countries and further assessed differences in ecotypes from four agro-ecological zones in Ghana. A total of 46 purple nutsedge samples: 40 samples from 40 communities across the study area and three each from two research stations were used for the study. The plants were multiplied, planted into pots and laid out in Completely Randomized Design with three replications. Qualitative and quantitative assessments were carried out on both underground and aboveground morphological traits of the weed samples. The qualitative traits of the samples generally conformed to those reported in other countries and did not vary significantly between the agro-ecological zones (P > 0.05). The quantitative (growth) parameters showed significant differences among agro-ecological zones (P < 0.05) and were generally smaller than those reported in other countries, suggesting morphological adaptation of the weed in Ghana. Samples from the transitional zone were significantly smaller and this could facilitate easier management of the weed in that area. The principal component analysis gave four latent factors, which mainly pointed to photosynthetic structures and growth characteristics as the major components determining variations in the collection. Cluster analysis gave four clusters (at 0.7 similarity index), which were related neither to their geographic origin nor to the agro-ecological zones.