Initial evaluation of Prosopis alba Griseb clones selected for growth at seawater salinities

In a previous article, growth and survival of Argentine and Peruvian Prosopis were measured in a greenhouse hydroponic system in which the salinities were increased from 10 to 45 dSm(-1). Twenty-one of the Prosopis alba seedlings that grew at the 45 dSm(-1) salinity were propagated by rooting cuttings and a seed orchard/long-term evaluation trial established. To develop predictors and/or correlations between seedling and performance in mature field trials, this study characterized the seedlings for growth, leaf, and thorn morphology and ease in asexual propagation by rooting of cuttings. The percentage rooting of all clones varied from 40 to 100%, the roots per cutting from 0.60 to 67, and the length of the longest root from 1.63 to 6.70 cm. The parent trees were selected from P. alba specimens in a highly saline area of Argentina where P. ruscifolia Griseb (which has larger leaves and 15 cm long spines) was the dominant species. Some progeny were intermediate in spine and morphological characters between P. alba and P. ruscifolia and were locally known as vinalillo (P. vinalillo Stuck). The thorn length varied from 7.7 mm to 53.3 mm for the vinalillo species'' and from 0 thorns to 28 mm for P. alba. There was no correlation between leaf/thorn characters and salinity tolerance. The overwhelmingly greater abundance of spiny P. ruscifolia over P. alba may be due to livestock palatability rather than salinity tolerance. The increasing demand for the high-quality Prosopis lumber for furniture may make recuperation of moderately saline soils (< 30 dSm(-1)) economically attractive.