Cloning of Elite, Multipurpose Trees of the Prosopis Juliflora/Pallida Complex in Piura, Peru
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Agroforestry Systems 54: 173–182, 2002. 2002 Kluwer Academic Publishers. Printed in the Netherlands. Cloning of elite, multipurpose trees of the Prosopis juliflora/pallida complex in Piura, Peru L. Alban1, M. Matorel1, J. Romero1, N. Grados1, G. Cruz1 and P. Felker2 1 Unidad de Proyectos Ambientales. Universidad de Piura, Piura, Peru; 2 Secretaria de Produccion y Media Ambiente, Santiago del Estero, Argentina Received 25 May 2000; accepted in revised form 10 January 2001 Key words: algarrobo, arid, budding, mesquite, nitrogen fixation Abstract The nitrogen fixing trees of the Prosopis juliflora/P. pallida complex are among the most adaptable and fastest growing trees in the truly tropical arid regions and have become naturalized in semi-arid tropics in Latin America, the Caribbean, Hawaii, Sahelian Africa, the Indian subcontinent and northern Australia. The trees have been regarded both as a serious weed and as a valuable resource for firewood and dune stabilization. Unfortunately the introductions into Sahelian Africa and the Indian subcontinent were from trees that had non-palatable pods. Despite their widespread occurrence, seed from a genetic improve- ment program is not available. Peruvian Prosopis has rapid growth, erect form and high survival of in Haiti, Cape Verde and India. An evaluation of form, diameter at breast height, pod production and pod palatability was conducted in a 10 year old plantation of 1,800 trees in Piura, Peru and seven were selected that had: more than 20 cm DBH; an erect form; 100% of branches with pods; and pods with a very sweet flavor. Scions and budwood were taken from these trees and successively grafted onto greenhouse grown stock plants to be used for clonal multiplication. For the first time we report successful chip budding grafting of Prosopis. This is the first report of Peruvian clones that have been selected for high produc- tion of highly palatable sweet pods. Introduction it. Due to the total lack of leaf drop with onset of winter temperatures and total lack of frost hardi- The nitrogen fixing trees of the genus Prosopis are ness of P. juliflora and P. pallida (as compared to an important component of many agroforestry other species such as P. alba, P. glandulosa), systems worldwide. Perhaps none of the 44 Felker (1990) has proposed that these tropical species of Prosopis (Burkart, 1976) has been as interbreeding species be treated together as a blessed and as maligned as Prosopis juliflora. complex. While P. juliflora has its origins in the true tropics While Prosopis pods were extensively of the Western Hemisphere (Caribbean, Mexico, consumed by indigenous peoples in the native Venezuela and Peru), it has been introduced to ranges of Prosopis in Peru (Diaz, 1994), North practically all the worlds’ arid zones. In India, P. America (Felger, 1977) and Argentina (D’Antoni juliflora was declared the Royal Plant of the State and Solbrig, 1977), the Prosopis pods in both of Jodhpur (Muthana and Arora, 1983) while in sub-Saharan Africa and India have bitter astrin- the Sudan and Australia it is officially classified gent tastes and are occasionally consumed by as a noxious weed with prohibitions to propagate livestock but not humans (Felker, P., unpub obs., 174 Felger, R. S. pers comm., 1996). We have found trees near the city of Piura. The mean annual considerable variability in the sweetness of the temperature, rainfall and class A pan evaporation pods in the native range, some pods being very were 24 C, 66 mm yr–1 and 1825 mm yr–1 respec- sweet and highly palatable while others are tively. astringent, bitter and acidic. Evidently the intro- Despite various taxonomic works on Prosopis ductions into sub-Saharan Africa and India were juliflora and P. pallida (Burkart, 1976; Ferreyra, from seed sources of the non-palatable type. 1987), considerable confusion exists on the The selection of clones of multipurpose trees taxonomy of the trees in northern Peru. While is more complicated than for trees that will only specimens can be identified that fit the description be used for single purposes such as lumber or of P. pallida or P. julifora, the presence of pulp. For lumber trees, a single trunk with minimal interspecific hybrids blurs these distinctions. branching is ideal. In contrast, a tree needs to have Therefore we have chosen to identify these clones a branched canopy with many locations for pod with a unique field location and a description of production. In addition, there is competition for their economically useful characters. photosynthate for trunk and pod production so that In August 1998, 22 plots representative of the trees with high pod production would be expected entire plantation were systematically selected for to have lower production of vegetative biomass a detailed forest inventory. Each of these plots in the form of timber. contained four rows of 10 trees per row (40 trees). The evaluation of selection parameters for The plots were separated by three rows of trees. multipurpose trees is also complicated. While tree A total of 880 trees of the 1,800 trees in the plan- diameter and height can easily be measured in the tation were measured (49%). The following mea- field on hundreds of trees, precise measurements surements were made; trunk height to first branch, of characteristics such as pod production and pod diameter at breast height (DBH), total tree height palatability is much more time consuming and/or and canopy diameter. In addition, the form was complicated. Therefore we have chosen to scored as: 1 = tree with multiple main stems below measure the easily quantifiable characters e.g., 1.2 m in height and branch angles greater than height and diameter by precise traditional methods 30 C; 2 = intermediate; and 3 = only one stem to and to employ visual ranking (based on verifiable minimum of 1.2 m in height and branch angles 30° criteria) to assess pod production and pod palata- or less. bility characters. In January 1999, a second evaluation of the entire plantation of 1800 trees was conducted and 3.7% of the trees were found to have a DBH Materials and methods greater than 20 cm. These trees were further evaluated for pod production and pod quality. Fruit The 9 ha plantation of 1,800 trees was established production was ranked as 0, 1, 2, 3, 4 with 0 being in January 1988 on the grounds of the Universidad without fruit; 1 = 25% of branches with fruit; de Piura, Peru (5°10′11″ S; 80°36′51″ W) with a 2 = 50% of branches with fruit; 3 = 75% of spacing of 10 by 5 m (200 trees ha–1). The soil branches with fruit; and 4 = 100% of branches texture was sand – 95.7%, silt – 2.6% and clay – with fruit. Following pod abscission, the ground 1.6%. The soil was alkaline (pH = 8.4), nonsaline surface under a tree with a rank of 4 was covered (EC = 0.5 mmhos), and low in organic matter with about 1 cm of pods equivalent to about 35 kg –1 –1 (0.12%), nitrogen (0.006%), K2O (102 kg ha ) tree . The fruit flavor was ranked as 0 = very –1 and P2O5 (13 mg L ). Due the low mean annual bitter; 1 = bitter; 2 = sweet; or 3 = very sweet. The rainfall (66 mm excluding Niño years of 2000 mm field was divided into plots, columns and rows to yr–1), the seedlings were drip irrigated for the first aid in the measurement of tree evaluation. four years until the trees reached permanent In August 1999, scions and budwood were groundwater at a depth of 10 m The seedlings taken from the mature trees to graft or bud onto were purchased from the forestry nursery of the unselected genetic stock in the UDEP greenhouse. Ministry of Agriculture in the city of Catacaos and Double English grafts and chip budding were were of unselected genetic stock collected from conducted according to the technique of Hartman 175 et al. (1996). Scions about 4 mm in diameter characteristics (Table 2). It is striking that slightly containing three to four nodes, were used and then less than half of this population (44.8%) had no wrapped with clear plastic tape. pods at all. Similarly, while we have observed that all these Peruvian pods have high sugar content, a very high percentage of these large trees (78%) Results had pods that had a bitter or very bitter taste. Therefore it is not surprising that previous intro- The mean total height, height to the first branch, ductions to Africa and India were from trees that canopy diameter and diameter at breast height in had pods unpalatable to humans. With respect to 1998 of 5.8 m, 1.7 m and 11 cm respectively, were tree form (with potential for fine lumber produc- quite respectable for 10 years growth at this low tion), 79% of the trees did not have an erect rainfall (Table 1). More promising is the fact that growth form. An example of one of the seven the great variability in the population permitted cloned trees (Figure 1) illustrates the narrow the possibility for selection for individual trees branch angle and erect form of this Prosopis. with outstanding performance. For instance, Out of the total of 67 trees with a diameter approximately 5% of the population had a greater than 20 cm, only 15 trees had the highest diameter at breast height twice the population pod production rank (100% of the branches with mean. pods). Only 10 of these 15 trees had good form The 3.7% of the 1800 trees that had diameter that would be suitable for lumber and of these, at breast height greater than 20 cm in 1999 was seven had pods that were sweet or very sweet.