Variability of stone pine (Pinus pinea L.) fruit traits impacting pine nut yield

Abstract

& Key message Cone to pine nut yield (PY), an important commercial feature of stone pine cropping, was higher in Chile than in main producer countries. PY is highly variable along years and depends on pine nut number inside cones, followed by pine nut weight. Cone morphometry is not a good indicator of PY, thus selecting cones for size/weight will not improve it. & Context Stone pine nuts are highly appreciated; however, pine nut yield (total pine nut weight as percentage of cone weight), important feature for the species cultivation, is variable and decreasing worldwide. & Aims Evaluating inter-annual and spatial variability of fruit traits impacting pine nut yield. & Methods Across years and plantation variability of fruit features were estimated from a multi-environment study monitored during 6 years in Chile. Variance component restricted maximum likelihood estimates were calculated for 14 fruit traits. Classification and Regression Tree (CART) was used to identify the variable best explaining pine nut yield. & Results Pine nut yield (3.6-5%) was higher than in main producer countries. Cone weight (521 g), length and diameter were correlated to most of seed and pine nut traits, but not to pine nut yield. The most important fruit trait in determining pine nut yield was pine nut number per cone, followed by pine nut weight. Pine nut yield showed high inter-annual and within plantation variability, whereas pine nut weight more spatial than temporal variability. Pine nut yield was superior in cones containing over 78 pine nuts. & Conclusion Pine nut yield has high inter-annual variability, with cone morphometry not being a good indicator, thus selecting cones for size/weight will not improve cone to pine nut yield.

Effects of geoclimatic factors on the variability in Pinus pinea cone, seed, and seedling traits in Turkey native habitats

“…The average SD and SL determined by Loewe-Muñoz et al (2018) were 1 and 2 cm, respectively, while in the present study, they were 0.9 and 1.8 cm, respectively; these latter measurements are similar to those reported by Ganatsas et al (2008) and Carcel et al (2012). Loewe-Muñoz et al (2019) report that the mean 6year measurement of SN in plantations in Chile was 113 which is more than double that found in the present study (50), with the Çanakkale-Kirazlı population having the lowest (25). A positive correlation was found between SN and CW; this finding supports several previous studies that have indicated that heavier cones contain more seeds Boutheina et al 2013;Loewe-Muñoz et al 2019).…”

“…Loewe-Muñoz et al (2019) report that the mean 6year measurement of SN in plantations in Chile was 113 which is more than double that found in the present study (50), with the Çanakkale-Kirazlı population having the lowest (25). A positive correlation was found between SN and CW; this finding supports several previous studies that have indicated that heavier cones contain more seeds Boutheina et al 2013;Loewe-Muñoz et al 2019). In our findings, the average cone to seed yield (SY) ranged between 8.1 and 18.5%, while Loewe-Muñoz et al 2019reported 6-year-mean values ranging from 17.7 to 22.6%.…”

“…Loewe-Muñoz et al (2016) suggested that the selection of sites for fruiting should ensure minimum average spring temperatures above 7°C, annual and autumn thermal oscillations below 12°C, and a high spring rainfall, except during the male flowering period. In the final year, losses in seed yield (with up to 50% of the seeds being empty) have been reported from Portugal, Spain, Italy, and Turkey (Mutke et al 2014), but in Chilean plantations, the percentage of damaged/empty seeds was relatively very low, at around 9% (Loewe-Muñoz et al 2019). We found that the overall sound seed ratio was 54%, ranging from 32 to 80%.…”

“…A limitation of this study was that it depended on 1year results, whereas inter-annual variations in seed production have been documented by several authors (Mutke et al 2005;Calama et al 2008Calama et al , 2011Calama et al , 2016Loewe-Muñoz et al 2019, 2020. Such variations could be the result of climatic factors affecting the 3-year reproductive development cycle of cones in stone pine.…”

“…For abbreviations, please see Table 2 CD, and CL resulted in increased PY. The PY is particularly interesting because of an increase of empty and damaged seeds (Loewe-Muñoz et al 2019), which have been associated with increased drought or phenological shifts due to climatic change (Mutke et al 2014) and infestation with Leptoglossus occidentalis Heidemann (Farinha et al 2018). Many studies have found that the seed size in many species is nonlinearly related to altitude and latitude, being dependent on low temperatures and radiation and a shorter growing season at higher latitudes or altitudes (Moles and Westoby 2003;Murray et al 2004;Moles et al 2007).…”