STONE PINE ORCHARDS for NUT PRODUCTION: Which, Where, How?
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Stone PINE ORCHARDS FOR Since the early nineties, several grafted NUT production: WHICH, clonal trials have been established in Spain within the framework of regional WHERE, HOW? and national research programmes for the characterization of the crop and the tested genotypes, elucidating the rele- The Mediterranean stone pine Pinus pinea vance of genetic and environment factors produces the genuine pine nuts or “pignoli” for seed-yield quantity and quality (Mutke used in Mediterranean and Arabian cui- 2005). In several analysed trials, the de- sine. Due to their supreme quality, they gree of genetic determination for average achieve higher prices than lower-quality annual cone yield (kg/tree) was estimated surrogates like seeds from the Chinese in 15-38%, resulting in an expected ge- Pinus koraiensis. On the Iberian Penin- netic gain of 12-39% selecting the top sula alone, stone pine covers more than 10% of the tested genotypes from each re- 550,000 ha, and Spain and Portugal are gional selection (with 90 candidate clones the main pine-nut producing countries. Al- each, whose ortets are plus trees selected though stone pine, a native or at least pro- in the pine forests for their outstanding tohistoric archaeophyte in most Mediterra- cone yield). The genetic correlations be- nean countries, is said to have been ‘cul- tween genetic values for cone yield and tivated’ since the Neolithic, actually hardly cone or seed size were always positive any effort seems to have been made for (r=0.17-0.47), hence no trade-off between its proper domestication as nut crop (or at crop quantity and quality is observed least to have achieved it): there are no de- (Mutke et al., 2005a; Mutke et al., 2007). fined cultivars, but nearly the whole current The approval of the best clones for the stone pine nut production is still harvested Spanish National Register of Basic Materi- from forest stands where no cultivation als is still pending, but it will allow the mar- techniques are applied except seeding or keting of their scions or grafts in the cat- planting of new stands, thinnings for stand egories ‘qualified’ or ‘tested’ as defined by density regulation and some pruning in the the Council Directive 1999/105/EC, of 22 lower or inner crown to ease manual har- December 1999, on the marke ting of forest One year old shoot of P. pinea tip-cleft (needle graft) grafted onto P. pinea. vesting or, historically, for fuel wood (Mutke reproductive material (OJEC of 15 January et al., 2000a). Even the small pine groves 2000, L 11/17-40), whose Annex I includes or isolated border trees so typical of Medi- Pinus pinea. on the vertical co-dominant shoots of the terranean rural landscapes are usually crown surface. This positive association seed-grown without known pedigree. This evaluation has allowed a selective at shoot scale between vegetative vigour rogueing of the clone banks and the esta- and reproductive investment contrasts with But the interesting market prices for pine blishment of the most promising clones in the classical model in fructiculture of a di- nuts and the crisis of traditional rainfed a new multi-site trial that will offer informa- chotomy between vigorous, vertical woody tion about their growth and fruiting habits crops in Mediterranean countries has shoots and weaker, bended fruiting shoots at different geographic locations. The im- drawn in the last years the attentions to so typical in most Angiosperm fruit spe- portance of this topic is evidenced by the Stone pine as an alternative woody crop cies, putatively due to a different phytohor- observed strong phenotypic plasticity of on farmland. In farmland afforestations monal regulation of apical differentiation stone pine growth and cone yield in de- after the CAP reform in 1992, stone pine than in stone pine. has been widely used for combining pu- pendence on soil properties and agrocli- blic subsidies with the expectation of fu- mate, as well as major clone-by-environ- The stone pine crown architecture pre- ture cone production (Mutke et al., 2000b; ment interactions at regional scale (Mutke, sents also a strong phenotypic plasticity ANSUB, 2006). Private initiatives have 2005). Currently, there is a gap of neat depending on light environment. In open- promoted intensively managed stone pine knowledge about site requirement and po- grown stone pines, the lateral branches plantations for pine nut production not only tential of this crop, though whilst genuine in full sun-light grow as much as or even in the Mediterranean area (especially in stone pine forests grow mainly on sandy or more than the leader shoot, sustaining Portugal), but even in several overseas rocky soils without agronomic value (that is also similar branching ratios and secon- countries like Australia or even Guatema- the ultimate reason that these woodlands dary growth that stiffen them in an ascen- la. In the last decade, cone gathering is in- escaped the ploughing up since Middle dant, co-dominant position, producing the creasingly made by harvesting machines, Ages), grafted plantations on farmland are typical polyarchic crown that is “wider than overcoming the shortage of skilled labour expected to render higher yields. for the dangerous pine climbing for cone deep”, spherical in youth and characteristi- dropping. Cultural Treatments cally umbrella-shaped in older trees, bear- Variety selection is not reasonable with- ing cones on the whole upper crown sur- CultiVAR SELECTION FOR GRAFTED out the development of specific cultural face. On the other hand, shaded branches plantations techniques adapted to this conifer as crop. in the inner crown or in the closed canopy In Italy, Portugal and Spain, research on Mutke et al. (2000a) stressed already some of denser stands show steep trends to grafting techniques and on clonal selec- difficulties in comparison with traditional reduce their successive yearly terminal tions has been undertaken aiming the im- woody crops due to the biology and char- shoot length as well as lateral bud number provement and standardizing of pine nut acter of the species (no rooting or woody per whorl, the supported needle mass and production in specific plantations or un- grafting, no adventitious sprouting abil- diameter increment, and to withdraw also der agroforestry systems (Baudín, 1967; ity that would allow crown renovation after female flowering, tending to masculinity. In Magini & Giannini, 1971; Catalán, 1990; pruning, etc.), of which the main one is the consequence, dense-grown stone pines Prada et al., 1997; Mutke et al., 2000a; location of female flowering exclusively on develop a vertical, monopodial crown ar- Castaño et al., 2004). the most vigorous annual shoot tips, i.e. chitecture similar to other pine species, 22 FAO-CIHEAM - Nucis-Newsletter, Number 14 December 2007 by a bud scion of the selected clone, using and only such altitudes or latitudes as with now preferentially container-raised root- risk of heavy snowfall advise against this stocks in greenhouse. crop, threatening to break down the open candelabra structure of the stone pine As in stone pine woody grafting is not fea- crown. Annual rainfall should be above at sible, scions are obtained from long shoot least 400 mm (best more than 600 mm) if terminal buds (still green soft tissue), well-grown cones (about 250-350 g) are best at the moment of starting the spring aimed, resisting the species strict summer flush. In order to allow a fast callus onset droughts by photosynthetic close-down and early sap supply between tissues, the (Mutke et al., 2006). stock might be slightly more advanced, af- ter bud burst though before complete shoot The response of pinecone yield to different elongation. Phenology thus constricts the spacing might be highlighted by the results most adequate time window to about two of two thinning experiences. The first one weeks each spring, in March in the warmer is an afforestation that had been grafted in southern coast area of Andalusia and not the field in 1987, five years after plantation before May in the Spanish inner highlands. (850 trees/ha; mass-selected, non-labeled But it can vary in several weeks between scions). After reaching complete closure years, depending on the accumulated day- of the grafted crowns few years later, in degree sum (Mutke et al., 2003). 1999 two-thirds of trees were extracted in a systematic thinning. The remaining trees The grafting point is tied up with a parafilm responded immediately with an increment ribbon and protected during several weeks of strobilus induction and since then, the both from water and from outdrying air by trees of the six thinned plots (8.5 m2/ha ba- a transparent perforated plastic bag. In the sal area, namely the sum of stem sections moment of grafting, stock branches are above the grafting point in 2006) render all cut back for avoiding competition with the years four- to ten-fold the mean yield of the scion; they are lopped completely in au- trees in the three unthinned control plots tumn once established the graftling’s own (BA 17 m2/ha), without significant yield dif- Two year old shoot of P. pinea g r a f t e d o n t o needle biomass. ferences between plots before thinning. P. pinea showing flowers. That is, the thinning nearly doubled the For rootstocks, no defined material is used, annual mean cone yield/ha from 180 kg to with tiers of small, dominated branches. but any well-formed seedling of Stone or 350 kg in the last six years. Only vigorously growing stone pine trees Aleppo pine serves (the latter for calcare- with ‘expanding’ crowns will hence render ous soils in thermo-Mediterranean climatic In another clonal orchard, planted in 1992 high cone yields (Mutke et al., 2005b).