Variation in thorn character within and among Prosopis species and vegetative multiplication of selected genotypes.
Seven species of Prosopis (one indigenous and the rest exotic) were screened with respect to their inter- and intra-specific variation in thorn character. P. pubescens showed a high frequency (55%) of thornless plants, followed by P. alba (26-30%). No plants of P. cineraria (the indigenous species) and P. tamarugo were thornless. The other 3 species (P. glandulosa, P. juliflora, P. velutina) had only 2.7-6.5% thornless plants. The most promising thornless trees from a 3-yr-old field performance trial were selected (excluding P. tamarugo, but apparently including P. cineraria) and tested for their ability to propagate vegetatively by cuttings and air layering. They were classified as easy to root, moderate and difficult to root. P. pubescens performed best, with 80% of cuttings and 96% of air layers rooting. Overall, air layering gave better results than shoot cuttings, and treatment of cuttings with IAA improved root induction. The study suggests possibilities for mass multiplication of desirable individuals long before seeds are produced.