Somatic embryogenesis, molecular characterization and genetic transformability of the Kenyan Jatropha (Jatropha curcas L.)

Abstract

Jatropha (Jatropha curcas L.) is considered a potential biofuel crop as it contains high amounts of oil in its seeds and has potential for other applications in agriculture and health. The major factors affecting Jatropha production include poor germplasm that is prone to pests and diseases, lack of knowledge on appropriate production methods and low genetic diversity, lack of quality planting material and lack of supporting government policies. The objectives of this research were to collect, document cultural and agronomic practices, characterize, regenerate Kenyan germplasm and carry out basic genetic transformation geared towards improvement for oil production. A total of 96 accessions were collected whereby 43.75 % were from Eastern, 16.67 % Rift Valley, 7.29 % Nairobi, 14.58 % Central, 10.42 % Western and 7.29 % from Coast. Production constraints recorded included pests and diseases, lack of market, unreliable rains, lack of quality planting material and limited management practices. In vitro regeneration showed that combination of 1.5 mg/l BAP, 0.6 mg/l Kinetin, 0.5 mg/l IAA and 0.1 mg/l Thiadiazuron gave best callus formation, shoot regeneration in the 4 accessions tested while 3.0 mg/l IBA and 3.5 mg/l NAA gave the best root formation. Accessions from Rift Valley showed the widest morphological diversity while those from Eastern and Coastal showed the least diversity. The phylogenetic and PCA analyses clustered the 69 accessions into three main clusters, Central, Coast and xx Western, Eastern, Rift valley and Nairobi accessions. GUS assay confirmed that the transformation efficiency was 44.43%. Jatropha production in Kenya suffers a wide range of production challenges which have attributed to its poor performance. Somatic embryogenesis of Jatropha was successfully established. The morphological and genetic differences among the accessions revealed by clustering into distinct groups suggest the presence of different sources of variations among the Jatropha accessions. This could be attributed to their diversity, geographical locations and also due to exchange of plant genetic resources among farmers within and between the regions. The moderate morphological diversity observed within the accessions points to ample possibilities of obtaining desirable trait combinations in Kenyan Jatropha. Available diversity and agronomic practices documentation can be used in future improvement of Kenyan Jatropha germplasm. This wide diversity can also be utilized in the selection of promising parents and inbred line development. Proper conservation of accessions studied could serve as raw material for the genetic improvement of different characters of the crop through recurrent selection after hybridisation. In vitro protocol regenerated developed could be used in production of elite accessions identified in mass for farmers. Transformation for specific traits should be done using the established transformation protocol to improve Jatropha production.