Distribution of commercial Mobydick (Gomphocarpus spp) grown in Kenya as revealed by morphological characterization
The genus Asclepias of Gomphocarpus subspecies commonly known as mobydick is currently grown commercially as a cutflower in Kenya. Asclepias refers to milkweed species grown in America and other Western worlds while Gomphocarpus refers to Asclepias species in Africa and Arabia continents. The varieties are distinguished mainly by boll characteristics which include size, shape, and plant height. In the farmers’ fields, Gomphocarpus physocarpus and Gomphocarpus fruticosus integrate to form a continuum and are difficult to distinguish. However, there is no precise data on the available commercial varieties of Gomphocarpus species grown and exported from Kenya. The species has recently been domesticated in Kenya but characterization has not been done. The objective of the study was to determine the distribution of major Gomphocarpus varieties in Kenya. A preliminary survey was done using the morphological characteristic of height to determine the prevalent type among farmers. The survey was conducted between April and June, 2011. The sampled areas were Machakos, Murang`a, Nandi, Nyeri, Bomet, Embu, Laikipia, Kisumu, Meru, Kajiado, Migori and Makueni districts. In order to get accurate information on the data collection sites, each farm was mapped by Global Positioning System (GPS) receiver; this instrument gave the altitudes (elevations), latitudes and longitudes of the sampled areas. A line level was used to establish the slope of the various sampled sites. Using boards graduated in the metric system, a distance of 10 metres between the boards was used. The board was moved up and down the slope until the spirit level showed that the string was horizontal. In this case, a difference in height of 10 cm would mean a slope of 1 %, whereas a height difference of 5 cm meant a gradient of 0.5% and 2.5 cm difference in height represented 0.25% gradient. A total of 145 farmers were selected at random and interviewed using a questionnaire. Soil samples were collected from sampled farms and analyzed in JKUAT laboratory using the hydrometer method. Materials used for soil structural analysis were water, sieves, hydrometer, sodium hexametaphosphate solution, amyl alcohol, soil dispersing stirrer, reciprocating shaker and soil textural triangle. The results showed that of the 145 farmers, 84.8% grew tall mobydick variety while 15.6 % grew the short variety. The results also indicate that 30.9% of all farmers growing the tall variety are in Machakos, Muranga (6.5 %), Nandi (11.4 %), Nyeri (14.6 %), Bomet( 7.3%), Embu (4.9 %), Laikipia ( 6.5%) , Kisumu (4.1%) , Meru (11.4 %) and the least were in Kajiado, Migori and Makueni each recording 0.8 %. As regards altitude, 84.8 % of all mobydick farmers grow the tall variety between 887-1388 m above sea level. Data collected on agro-ecological zones indicate that mobydick grows across UM4, LU4, UM2, LM4, SU3, LM3, LM1 and LM5 with 84.8 % of all farmers growing the tall variety. In conclusion, the tall variety is the most dominant of the commercial mobydick varieties among the Kenya farmers. The variety also dominates all agro-ecological zones at the current status.
Key words: Asclepias, characterization, cutflower, distribution, Mobydick