Field pea (Pisum sativum L.) is highly susceptible to ascochyta blight, primarily caused by the pathogen Mycosphaerella pinodes (Berk. & Blox.) Vestergr. Grasspea (Lathyrus sativus L.) has been reported to possess a moderate level of resistance to ascochyta blight caused by M. pinodes. The work reported in this thesis aimed to develop the various techniques that would be required to transfer ascochyta blight resistance from grasspea into field pea via somatic hybridisation. This thesis also assesses the feasibility of achieving this goal. Field pea shoot cultures were established on hormone-free MS medium, and a protoplast isolation protocol developed for both species. Grasspea shoot cultures were established on both RL and SSB8 medium. Friable grasspea callus was achieved on media supplemented with 2,4-D in the range 4.523 µM, whereas kinetin tested at any concentration did not appear to influence callus growth. A suspension culture of grasspea was developed for the first time, in B5 medium supplemented with 4.5 µM 2,4-D and 0.5 µM kinetin. Grasspea protoplasts were isolated from both in vitro seedlings and suspension cultures. Protocols for hybrid shoot culture on KM8p medium were developed via organogenesis and somatic embryogenesis.

Field pea (Pisum sativum L.) is highly susceptible to ascochyta blight, primarily caused by the pathogen Mycosphaerella pinodes (Berk. & Blox.) Vestergr. Grasspea (Lathyrus sativus L.) has been reported to possess a moderate level of resistance to ascochyta blight caused by M. pinodes. The work reported in this thesis aimed to develop the various techniques that would be required to transfer ascochyta blight resistance from grasspea into field pea via somatic hybridisation. This thesis also assesses the feasibility of achieving this goal. Field pea shoot cultures were established on hormone-free MS medium, and a protoplast isolation protocol developed for both species. Grasspea shoot cultures were established on both RL and SSB8 medium. Friable grasspea callus was achieved on media supplemented with 2,4-D in the range 4.523 µM, whereas kinetin tested at any concentration did not appear to influence callus growth. A suspension culture of grasspea was developed for the first time, in B5 medium supplemented with 4.5 µM 2,4-D and 0.5 µM kinetin. Grasspea protoplasts were isolated from both in vitro seedlings and suspension cultures. Protocols for hybrid shoot culture on KM8p medium were developed via organogenesis and somatic embryogenesis.

Experiments were conducted to determine the outcrossing rate, the inheritance of markers and establish a basic linkage map in grasspea, <i> Lathyrus sativus </i>L. The outcrossing rate in a white-flowered line of grasspea ranged from 1.7 to 2.7% among eight combinations of gene frequency and location. The outcrossing rate in this study (2.2 ± 0.7%) suggests that individual lines of grasspea should be maintained in isolation to maintain their genetic integrity. Inheritance and linkage were determined for one morphological, 11 isozyme and 72 RAPD markers in five F₂ populations (all RAPD markers were in one F₂ population). The inheritance of flower colour was monogenic with colour dominant over white. The isozymes, ACO-1, ACO-2, AAT-1, AAT-2, EST-6, FDH, LAP-1, PGD-2, SKDH and TPI-1, were codominantly expressed with monogenic inheritance. The isozymes LAP-1 and PGD-2 segregated in a non-Mendelian ratios in the crosses PI 426891.1.3 x PI 283564c.3.2 and PI 426891.1 x PI 172930.4, respectively. The isozymeEST-3 was monogenically inherited and dominantly expressed. Most RAPD markers segregated in a 3:1 ratio. Marker UBC368_425/655 segregated in a co-dominant fashion. The RAPD markers UBC304₈₃₁, UBC304₉₆₄, UBC308₉₉₀, UBC322₁₄₃₂, UBC328₈₃₁, UBC332₁₁₁₈, UBC3321₁₅₈₁, UBC333₆₁₇, UBC349<sub>752<?sub>, UBC365₁₀₁₃ and UBC388₄₅₉ showed distorted segregation. In two F₂ populations, PI 283564c.3 x PI 426885.2 and PI 358601.5 x PI 173714.5, a linkage between AAT-2 and SKDH was reconfirmed. In the cross PI 426891.1.3 x PI 283564c.3.2, one morphological, three isozyme and 71 RAPD markers were mapped resulting in the delineation of 14 linkage groups including 69 markers (1 morphological, 3 isozyme and 65 RAPD markers). The total genome length covered by these 75 markers (69 linked and six unlinked) was about 864 cM. Considering cost, simplicity and abundance, RAPD analysis was more efficient than isozyme analysis in developing linkage map.