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Fourteen probes were selected and used in dot-hybridizations
and Southern hybridization analyses for the differentiation of
SPWB-MLO from various MLOs.Two probes SPWB16,SPWB27 hybridized
with DNAs from SPWB-MLO affected plants but not with DNAs from
healthy plants and plants infected with other MLOs. Twelve
other probes (SPWB5;SPWB8;SPWB12;SPWB15;SPWB25;SPWB28;SPWB36;
SPWB54; SPWB59;SPWB62;SPWB73;SPWB99) hybridized with DNA from
plants affected with SPWB, PNWB but not with DNA from healthy
plant and other MLOs. The specific probes detected the DNA from
periwinkle infected with SPWB-MLO to 0.05-0.1ng and the DNA
from sweetpotato infected with SPWB-MLO to 0.3-0.7ng
effectively. In the Southern hybridization analyses,nine of the
probes though crossreacted to PNWB-MLO in dot-hybridization can
differentiate the SPWB-MLO from PNWB-MLO. A polymerase chain
reaction(PCR)method has been applied in the detection of SPWB-
MLO. Primers were selected from SPWB54. Amplification of SPWB-
MLO DNA with 1.1 kb in length had been achieved with DNA from
SPWB,PWB-MLO affected plants but not with DNA from healthy
plants and plants infected with other MLOs after 25 cycles of
reactions. To evaluate the minimal amount of DNA required for
the amplification of MLO-specific DNA ,an MLO-DNA fragment was
obtained after amplification of 10pg of total DNA from diseased
plants after 35 cycles of reactions, respectively.
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