Interspecific graft incompatibility in Prosopis.
Prosopis spp. have been recognized as valuable for reforestation in semiarid regions. Self-incompatibility and the mandatory outcrossing of the species results in a high degree of genetic variability, resulting in a need for asexual propagation of trees wih desirable characteristics. In addition, the use in such regions of weedy, unimproved, naturally-occurring Prosopis spp. as rootstocks for superior grafts may avoid some of the difficulties associated with seedling establishment in semiarid regions (low moisture, high winds, grazing pressure etc.). Five species from section Algarobia (Prosopis articulata, P. chilensis, P. juliflora, P. glandulosa var. torreyana and P. alba) and one species from the section Strombocarpa (P. tamarugo) were reciprocally grafted to each other to determine their graft compatability. All species from section Algarobia were graft compatible with each other. Graft compatibility barriers apparently exist between P. tamarugo from the section Strombocarpa and the species from section Algarobia. A simple and effective method for grafting was identified following a comparison of T-bud (0% successful), side-veneer (47%), cleft (67%), and whip and tongue (67%) graft types. The cleft method was chosen due both to its relative easiness and the uniformity achieved with large numbers of grafts.