3 research outputs found
Susceptibility to ergot in Zimbabwe of sorghums tbat remained uninfected in their native climates in Ethiopia and Rwanda
Forty-four local Ethiopian and Rwandan sorghums (Sorghum bicolor) were observed to remain free of
ergot, or had only low incidence, in their natural equatorial latitudes and were potentially of interest, in
the design of male-sterile lines for F| hybrid breeding, if they possessed a physiologically based resistance
mechanism. These sorghums were therefore also investigated under natural and artificial disease
pressures in Zimbabwe where unadapted development and inappropriate long daylengtb prevented
flowering in 18 accessions. Of the remaining 16 Ethiopian and 10 Rwandan accessions which flowered,
only one from each country remained free of ergot. The susceptibility expressed was ascribed to observed
asynchrony of stigma exsertion with anthesis. In the Rwandan accession that persistently remained free
of ergot in Zimbabwe, histology of ovules showed pollination before floret gaping, so that a general
principle of disease escape due to efficient pollination is proposed for the Ethiopian and Rwandan
sorghums in their native climates. The findings emphasize that cleistogamy is a desirable character for
avoiding ergot infection in self-fertile sorghums and suggest that the Ethiopian and Rwandan sorghutns
may not generally be useful for breeding ergot-resistant male-sterile female lines. However, a few
accessions deserve more detailed study as a potential genetic resource, before a firm conclusion that all
apparent resistance is disease escape owing to efficient pollination