In vitro propagation of miracle berry (Synsepalum dulcificuDaniel) through embryo and nodal cultures

Miracle berry is an evergreen tropical shrub which modifies sour food to produce a sweet taste. Its propagation is, however, hindered by seed recalcitrance and difficulty of stem to root. Thus in vitro propagation was investigated through embryo and nodal explants using different levels and combinations of auxins and cytokinins in MS medium. Embryo was regenerated in MS medium supplemented with 0.1 mg/l NAA + 0.2 mg/l BAP. Lateral buds proliferation was induced on thegerminated embryo with 0.6 - 3.0 mg/l BAP + 0.1 - 0.2 mg/l NAA in which 3.0 mg/l BAP + 0.1 mg/l NAA produced highest number of buds. Rooting of the embryo regenerated plantlets was achieved with 1.0 -2.0 mg/l IBA + 0.1 mg/l BAP. Very low (5 - 10%) axillary and terminal buds formation was achieved from nodal cultures. Few of the nodal explants formed buds with 0.1 - 0.8 mg/l NAA + 0.2 - 1.0 mg/l BAP +0.02 mg/l GA3 with 0.8 mg/l NAA + 0.2 mg/l BAP producing the best result. However, all efforts to induce rooting on the buds formed from nodal explants proved abortive

Effects of single and mixed infections of blackeye cowpea mosaic virus and cowpea aphid-borne mosaic virus on cowpea

The response of cowpea (Vigna unguiculata) inoculated with Blackeye cowpea mosaic virus (BlCMV), Cowpea aphid-borne mosaic virus (CABMV), and BlCMV+CABMV was investigated under screenhouse conditions, using completely randomised design with six replications. Seedlings of the cowpea line TVU 76 were mechanically inoculated at 10 days after sowing. Uninoculated cowpea plants served as controls. Disease incidence, severity and yield parameters were recorded. Virus concentration in leaf samples was determined using Antigen Coated Plate-Enzyme Linked Immunosorbent Assay (ACP-ELISA). One hundred percent infection was obtained at two weeks post inoculation regardless of the virus combination. CABMV and BlCMV+CABMV elicited the highest symptom score of 4 while the lowest score of 2.8 was observed in BlCMV-inoculated plants. Mixed infections enhanced the highest virus concentration (1.7). The virus titre value in plants infected with CABMV (0.8) was relatively higher than in the BlCMV-inoculated plants (0.5). The seeds from uninoculated plants gave the highest (2.1 g) weight. Mixed infections with BlCMV+CABMV resulted in the lowest seed weight per plant (0.4 g), followed by single infection with CABMV (0.7 g), whereas the value was 0.8 g in the BlCMV-infected plants. Adoption of cowpea cultivars with genetic resistance against multiple virus infections is recommended in order to guard against complete crop failure.Keywords: Disease incidence and severity; seed weight; Vigna unguiculata; virus concentratio