> The white pine blister rust pathogen is a typical heteroecious, macrocyclic rust that produces five distinct spore stages on two different hosts to complete its life cycle. The pycnial stage consists of pycniospores, or spermatia, which are haploid spores that fertilize compatible receptive hyphae. The two sexes are not distinguishable and are simply designated plus and minus. This is the stage where genetic recombination can occur that may lead to development of races of the rust. However, the nuclear cycle (i.e., dikaryogamy, diploidization, meiosis) of the blister rust fungus has not been fully determined, but is assumed to be the same as for other better known rust fungi such as Puccinia graminis. The aecial stage develops in host tissue occupied by pycnia the previous season (Figure 6). The fungus is perennial in the pine host and aeciospores are produced annually as long as the host tissues remain alive. Aeciospores are disseminated by wind over long distances, and Ribes spp. as far as 480 km (300 miles) from the nearest known white pines have been infected.
> The white pine blister rust pathogen is a typical heteroecious, macrocyclic rust that produces five distinct spore stages on two different hosts to complete its life cycle. The pycnial stage consists of pycniospores, or spermatia, which are haploid spores that fertilize compatible receptive hyphae. The two sexes are not distinguishable and are simply designated plus and minus. This is the stage where genetic recombination can occur that may lead to development of races of the rust. However, the nuclear cycle (i.e., dikaryogamy, diploidization, meiosis) of the blister rust fungus has not been fully determined, but is assumed to be the same as for other better known rust fungi such as Puccinia graminis. The aecial stage develops in host tissue occupied by pycnia the previous season (Figure 6). The fungus is perennial in the pine host and aeciospores are produced annually as long as the host tissues remain alive. Aeciospores are disseminated by wind over long distances, and Ribes spp. as far as 480 km (300 miles) from the nearest known white pines have been infected.