BOLETIM DA FACULDADE DE CIÊNCIAS AGRÁRIAS DO PARÁ, n.9, dez.1977

Abstract

1) Seeds of peas were treated with different concentration levels of colchicine and different exposition times to obtain poliploid plants. Stomata analysis revealed that four plants proceeding periods were likely to be poliploid plants.

2) Eight different species of the Hevea genus were subjected to tapping on a comparative basis during three consecutive years. A half-spiral tapping system was used on alternate days with 55% intensity. The number of plants of each species waried between 10 and 15. The species studied were: H. brasiliensis, H. benthamiana, H. guyanensis, H. viridis, H. pauciflora, H. rigidifolia, H. microphylla and H. spruceana. The following conclusions were draw: 1) H. brasiliensis yielded the highest amount of dry rubber per tree per tapping roughly 50% more than H. benthamiana and H. guyanensis; 2) In spite of the relatively small number of trees, a great variation in yeld was observed among individual plants in ali species. The highest producing tree was one of the H. benthamiana species with an average yeald 60,24g of dry rubber per tapping. Among the trees of the H. pauciflora species, one was outstanding with an average yeald of 18,5 g of dry rubber per tapping: 3) It is kwon that the H. benthamiana species, generaly speaking, is more tolerant to the Microcyclus ulei (leaf blight disease) than H. brasiliensis. H. pauciflora is immune to that pathogen. So there is a good possibility of obtaining high-yealding specimens through selection of native plants and there seems to be a good chance of using pure trees of these two species for industrial plantings. The rubber from the two species, H.benthamiana and H. pauciflora, is comparable to that of H. brasiliensis.

3) Rubber tree (Kevea spp) showing látex overflowing and borers perforation were cut for counting of insects found superficially on the bark. Daily counts of adult insects appearing from the trunk and branches were made in laboratoy conditions with the purpose of observing the level of diferent borers infestation, taxonomic identification and also for a future study on the mecanism of parasitism and the complexe Insect/Fungus/Host to evaluate the "causa mortis' of those trees in the State of Para (Brazil).