Abstract
Prosopis alba seedlings, that grew at the 45 dS m−1 salinity level in a previous study of growth and survival of Argentine and Peruvian Prosopis, were propagated by rooting cuttings and established in a seed orchard/long term evaluation trial on soils with low salinity (EC 5.1–7.5 dS m−1) but high pH (8.9 to 10.2). A pH gradient occurred in the field with values ranging from pH 9.4 in block 1 to pH 10.3 in block 5. After five years growth, almost all of the clones had a mean height greater than 4 m and one clone was more than 5 m. Ten of the 21 tested clones had significantly greater biomass growth than the three seed propagated check varieties. The broad-sense (i.e., clone mean) heritability was estimated to be 0.45 for biomass, 0.53 for diameter and 0.59 for height indicating that strong genetic gains should be possible by selecting and vegetatively propagating the best genotypes. In the block with the highest pH values, two clones that appear to be P. alba × P. ruscifolia hybrids (i.e., P. vinallilo) had the greatest biomass. Correlations between growth during the last two months in the high salinity hydroponic greenhouse selection system and growth in the field were significant (R2 = 0.262) and positive, although the relationship was negative for putative P. vinallilo clones (R2 = 0.938). The several fold increase in biomass of some of the clones over the three check varieties, suggests that the greenhouse screen was successful in identifying superior salt tolerant clones. Apparently whether the greenhouse seedlings had lesser (~1 cm) to greater (~3 cm) height growth was not as important as just having a healthy live apical meristem. The observed salt tolerance of the putative P. vinalillo clones may prove useful as rootstocks for recently described high pod producing P. alba clones.
Highlights
According to FAO, approximately 400 million ha are affected by sodic or saline soils [1]
The Peruvian P. pallida species are not adaptable to Argentina due to lack of cold hardiness and P. alba is more amenable to lumber production than the P. flexuosa and P. ruscifolia evaluated in the hydroponic system
The soil pH and salinity of this trial are shown in Table 1 where it can be seen that the salinity was far less than the 45 dS m−1 level that was used to select the initial seedlings
Summary
According to FAO, approximately 400 million ha are affected by sodic or saline soils [1]. Among the recommendations for applied research by an FAO expert committee were development of salt-tolerant crop varieties and the use of Salicornia, Atriplex, Salvadora and Prosopis as a good alternative in salt-affected areas [2]. Nitrogen fixing trees of the genus Prosopis show promise for the rehabilitation of saline soils in subtropical regions because of their high salt tolerance and because they have economically useful products that can provide the economic incentive to drive the restoration of saline lands. Several of the largest P. alba lumber, flooring, and furniture companies have ceased operations due to the severity of this degradation [5]
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