|dc.description.abstract||Two semi-selective media, MT and MSP, were compared for their ability to recover cells
of the bacteria Xanthomonas axonopodis pv. phaseoli (Xap) and Pseudomonas syringae
pv. phaseolicola (Psp), the causal organisms of bean common and halo blights
respectively. Isolates Sx70 and Sp75 (for Xap and Psp respectively) were plated on the
media by dilution plating. Greater number of Xap colonies on MT than on MSP was
obtained, but the number of Psp colonies was not significantly different on the two
media. Four media, XCP1, MT, MT(new), and TSM were also compared for the number of
contaminants and Xap colonies grown on them, using data obtained from ISTA/ISHI
Comparative test for Xap (2002), which was conducted at the Agricultural Research
Council (ARC) in Roodeplaat, north of Pretoria. In most cases, the number of colonies
was similar in XCPI, MT, MT(new), but bigger in TSM. The number of contaminants was
smaller in MT than in MT(new).
Bean plants (Phaseolus vulgaris), variety PAN 146, were grown and inoculated with the
bacteria Xap and Psp, and two virus isolates of bean common mosaic virus (BCMV).
Uninoculated controls were also grown. Germination and vigour tests were conducted on
the seeds harvested from these plants. Germination was significantly lower for seeds
harvested from Psp inoculated plants, while seed vigour was reduced both for seeds
harvested from Psp and Xap inoculated plants. Neither germination nor vigour was
affected for seeds from BCMV inoculated plants. Late and early matured seeds from the
BCMV inoculated plants were compared for the virus transmission and emergence. There
was greater virus transmission and reduced emergence in the late matured seeds than in
the early matured ones.
Seeds harvested from Psp and BCMV inoculated plants and uninoculated controls were
unexpectedly found to be infested with the bean weevil (Acanthoscelides obtectus (Say)).
The BCMV infected batch of seeds appeared to repel weevil attack, whereas 25% of the
uninfected batch of seeds were attacked.||en