Host relationships of fusiform rust disease: I. Infection and pycnial production on slash pine and nearby tropical relatives
Doudrick, R.L.; Schmidtling, R.C.; Nelson, C.D.
Silvae Genetica 45(2-3): 142-149
ISSN/ISBN: 0037-5349 Accession: 008783490
Seedlings from 8 sources of slash pine (Pinus elliottii var. elliottii and var densa) and from 2 sources each of Caribbean pine (P. caribaea var. caribaea) and West Indian pine (P. occidentalis) were inoculated using inocula obtained from 2 sources of Cronartium quercuum f. sp. fusiforme, the causal agent of fusiform rust disease. The percentage of infection, evident primarily as galls and sporulation of pycnia of C. q. fusiforme, differed significantly within sources of slash pine and among species. The percentage of infection of all inoculated shoots was highest on slash pine (P. e. densa) seedlings from south Florida (92%) and lowest on P. occidentalis (30%). Among slash pine seedlings, the general trend was more pycnia sporulation on seedlings from sources nearest the origins of inocula, with the only exception being on those of P. e. densa from the most southern source, which showed abundant sporulation of pycnia similar to seedlings P. c. caribaea from a nearby source. No sporulation occurred on seedlings of P. occidentalis. Differences among families within sources of slash pine were significant for percentages of infection and sporulation of pycnia on all shoots inoculated using C. q. fusiforme. Because sporulation of pycnia is a prerequisite for fecundity in C. q. fusiforme, the results suggest strong selection on natural inoculum for infection and fertility among and within sources of slash pine. Breeding strategies currently recognize families of slash pine that minimize damage due to fusiform rust disease, but new strategies might consider limiting pathogen reproduction.