DISTRIBUTION OF COMMERCIAL MOBYDICK (GOMPHOCARPUS SPP) GROWN IN KENYA AS REVEALED BY MORPHOLOGICAL CHARACTERIZATION

Abstract

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.