Pomological Characterization of Main Almond Cultivars from the North Eastern Morocco

ABSTRACT

This study concerns pomological characterization of four almond cultivars (Ferragnes, Ferraduel, Marcona and Fournat) introduced in eastern Morocco. The aim is to determine recommended cultivars for this region. Several nut and kernel pomological traits were determined, nut weight ranged between 2.65 g for Ferragnes and 4.41 g for Fournat, and kernel weight ranged between 0.73 g for Marcona and 1.38 g for Fournat. Volume of nuts and kernels ranged, respectively, between 4000.98 mm³ for Ferragnes to 846.09 mm³ for Marcona and 9667.20 mm³–1553.01 mm³ for Fournat. Finally, Ferragnes, Ferraduel and Fournat have kernel yields, reaching 33%, against 20–23% for Marcona which is the most sensitive to drought

KEYWORDS:

• Almond cultivars
• nuts
• kernels
• pomological traits

Introduction

Almond tree (Prunus amygdalus L.) belongs to the Rosaceae family and it is an important nut crops worldwide (Chin et al., 2014). The almond tree can grow in different distinctive pedoclimatic conditions, with remarkably drought resistance (Laghezali, 1985). This culture is widely spread in the world, but the productivity is restricted by some ecological factors as late spring frost (Polat et al., 2001) which causes significant damage to the flowers and therefore a decrease in fruit production (Kodad et al., 2011). In Morocco, almonds are the most important nut crops with an area of 151 000 ha and an average production of 99.000 tons. In eastern Morocco, the plantations of almond trees cover 10% and produce 15% of Morocco almond kernels (MAPM, 2015). Recently, almond culture in this region is supported by a Belgium program for agriculture and rural development (PROFAO 2011–2017:The almond value chain in eastern Morocco, Pillar II of the Moroccan Green Plan, supported by Belgian development agency (BTC 2011–2017)). Indeed, low almonds production in the traditional culture is due to drought; moreover, native genotypes, growing in marginal land and under unfavorable rain fed conditions, are usually early blooming and consequently their flowers and early-developing fruits are damaged by late spring frost. Thus, to improve quantitative and qualitative production of almonds in this region, PROFAO allowed the introduction of new varieties for planting 6.000 ha of new orchards and the set up of new crushing plants for almonds in shell. The target of PROFAO is to increase almonds production and to make this culture enough profitable for rural people in eastern Morocco.

Four European almond cultivars (Ferragnes, Ferraduel, Marcona and Fournat) were used for the plantation of new orchards in this region. Ferragnes/Ferraduel (F/F) is the main couple among them, known for the late flowering in March permitting to escape the spring frost damages (Melhaoui et al., 2017). This pair of cross-pollinated cultivars is usually growing together in the same orchard. Marcona and Fournat are the two other introduced cultivars in this region characterized also by a late flowering period begins at the end of February (Bernad and Socias i Company, 1995; Melhaoui et al., 2017).

No studies have been undertaken on the domestication and behavior of these introduced almond cultivars in eastern Morocco. Moreover, nut and kernel physical traits have been considered so far in almond quality evaluation (Socias i Company et al., 2010 For these reasons, this study aims to determine some pomological characters of the main introduced cultivars (Ferragnes, Ferraduel, Marcona and Fournat), in five zones of this region. Thus, this work focuses on pomological characteristics of nut and kernel of each almond cultivar, kernel percentage and the double kernels as well. The results occurred would be useful to determine the most adapted cultivars to the climate of this region with the aim to improve the almond production and rural producers’ incomes

Materials and Methods

This study concerns five different areas of eastern Morocco As indicated in Figure 1. Thanks to PROFAO, these five areas have benefited from a large program of new almond plantations, which reached 4000 ha in 2015 and will continue until 2018 (MAPM, 2017). The studied plantation areas and their geographic coordinates are in Table 1, they are characterized by, annual temperatures ranging between −2°C and 43°C, a frost period from December to February and an average annual precipitation between 100 mm and 300 mm. The cultivation of almond trees is essentially rain-fed, but for good growth, yield, quality of crops and longevity of the orchard, extra irrigations are provided to almond trees to meet their minimum water needs.

Table 1. Geographical coordinates of almond growing areas covered by this study.

Zone no.	Municipalities	City	Geographical coordinates
1	TANCHERFI	Taourirt	34°21ʹ09.1ʹ’ N, 002°37ʹ31.2ʹ’ W
2	MECHRAA HAMMADI	Taourirt	34°43ʹ01.6ʹ’ N, 002°27ʹ59.0ʹ’ W
3	SIDI BOUHRIA	Berkane	34°44ʹ13.6ʹ’ N, 002°20ʹ15.0ʹ’ W
4	RISLANE	Berkane	34°44ʹ39,3ʹ’ N, 002°27ʹ00.2ʹ’ W
5	BSARA	OUJDA	34°42ʹ23.1ʹ’ N, 002°13ʹ38.7ʹ’ W

Figure 1. Geographic localization of almond plantation in eastern Morocco and the zones studied.

Total area of each orchards studied is between 3 and 5 ha. We selected teen orchards (two orchards by studied zone), which are undergoing the same agricultural practices. Six almond trees were chosen in each orchard and 40 fruits were harvested from each cultivar. Thus, this pomological study is carried out with a sample of 800 almond fruits. Quantitative traits were investigated on the basis of the almond descriptors developed by the International Plant Genetic Resources Institute “IPGRI” (Gülcan, 1985). As indicated in Figure 2, the main recorded traits for each cultivar were fruit and kernel weight (g), fruit and kernel width (mm), fruit and kernel length (mm), fruit and kernel thickness and kernel percentage. A digital caliper with accuracy of +0.01 mm was used for width measurements. Nut and kernel mass was measured with an electronic balance of 0.0001 g sensitivity.

Figure 2. The measurement of fruit and kernel dimensions.

The sphericity (φ) of nuts and kernel, the geometric mean diameter (Dg), and the volume (V) of the nuts and kernels are determined as follows (see Perez et al. 2007; Mirzabe et al. 2013):

(1) $\phi =\sqrt[3]{\mathrm{L}\mathrm{W}\mathrm{T}}+\frac{100}{\mathrm{L}}$(1)

(2) $\mathrm{D}\mathrm{g}=\sqrt[3]{\mathrm{L}\mathrm{W}\mathrm{T}}$(2)

(3) $\mathrm{V}=\frac{\pi \ast D{g}^3}{6}$(3)

where L is the length, W is the width and T is the thickness. Statistical analyses were performed with the SPSS software for Windows (SPSS.21, USA). Values of different parameters are expressed as the mean value. The normal distribution was verified according to Shapiro–Wilk test. Duncan’s method was used for mean comparison. Only variables with a confidence level superior to 95% (P < 0.05) were considered as significant.

Results and discussion

This work focuses on intra-varietal and inter-varietal comparison of pomological characters of nuts and kernels of the studied almond cultivars. As can be seen in Tables 2 and 3, the five studied agricultural zones produce different kinds of almond and significant differences are revealed in terms of analyzed parameters. Indeed, physical traits of nuts and kernels of the studied almond cultivars show differences for the analyzed parameters such as length, width, weight, thickness, geometric diameter (Dg) sphericity and volume and these differences are statistically significant for both nuts and kernels (Tables 2 and 3). Furthermore, due to their economic interest, double kernel rate and shelling percentage (kernels yield) were determined for each cultivar in the five studied zones (Table 3). The observed results show clearly inter- and intra-varietal differences. These differences are statistically significant at 5%, between all studied pomological traits of the four almond tree cultivars (Tables 2 and 3). Thus, in “Rislane zone”, almond nuts of Ferragnes show the lowest values for weight (2.65 g) and the width (19.63 mm); however, the highest values (4.41 g) and (27.65 mm) were registered for Fournat in “Tancherfi Zone”. In this zone, for Ferragnes/Ferraduel, nuts’ weights are 3.52 g and 4.22 g, respectively, and they are similar to results observed by Ak et al. (2005). Concerning almond nuts length and thickness, Marcona had the lowest nut length (26.15 mm) in “Labsara zone” but Fournat showed the highest nuts length (41.15 mm) in “Tancherfi zone”; however, Ferraduel had the lowest nut thickness (13.65 mm) in “Mechraa Hammadi zone” while Marcona shows the highest thickness (16.86 mm) in “Rislane zone.

Table 2. Nut traits of four almond cultivars, Ferragnes, Ferraduel, Marcona and Fournat cultivated in five different zones [(1) Tancherfi; (2) Mechraa Hammadi; (3) Sidi Bouhria; (4) Rislane; (5) Bsara] of North Eastern Morocco.

Parameters	Zone	Marcona	Fournat	Ferragnes	Ferraduel
Weight (g)	1	4.26^a β	4.41^a β	3.51^ab α	4.22^a β
	2	3.14^b ɤ	3.55^ab ɤ	3.68^a α	2.69^b β
	3	3.18^b ɤ	3.62^a α	3.47^b α	3.88^c β
	4	3.88^c ɤ	3.34^b δ	2.65^c α	3.11^d β
	5	3.46^d α	3.30^b α	3.33^b α	3.33^d β
Width
(mm)	1	25.07^a ɤ	27.65^a δ	21.84^a α	24.39^a β
	2	22.58^b α	24.25^b β	22.00^a α	22.40^b α
	3	22.73^b α	25.42^c β	22.68^b α	25.17^c β
	4	24.86^a ɤ	24.33^b δ	19.63^c α	20.84^d β
	5	23.50^c β	24.86^cb ɤ	21.74^a α	23.06^b α
Length
(mm)	1	28.88^a ɤ	41.15^a δ	33.74^a α	35.04^a β
	2	26.48^b ɤ	34.57^b δ	33.36^a α	31.41^b β
	3	26.55^b ɤ	36.54^c β	32.74^a α	35.47^a β
	4	27.94^c α	34.85^b β	28.02^b α	27.61^c α
	5	26.15^b ɤ	35.23^b δ	32.67^a α	32.12^b β
Thickness
(mm)	1	16.07^a β	16.16^a β	14.19^ab α	14.26^ab α
	2	14.47^b ɤ	14.07^b δ	15.04^c α	13.65^a β
	3	14.54^b α	15.37^c α	15.41^c α	15.53^c α
	4	16.86^c ɤ	14.96^d β	13.83^a α	14.98^bc β
	5	15.57^d ɤ	14.93^d α	14.94^bc α	14.19^ab β
Geometric diameter
(mm)	1	22.66^a β	26.38^a ɤ	21.86^a α	23.00^a β
	2	20.52^b ɤ	22.74^b α	22.26^ab α	21.25^b β
	3	20.62^b ɤ	24.25^c β	22.39^b α	24.00^c β
	4	22.70^a ɤ	23.31^d δ	19.66^c α	20.44^d β
	5	21.22^c β	23.55^d ɤ	21.97^ab α	21.88^b β
Sphericity %	1	78.48^a β	64.15^a α	64.85^a α	65.72^a β
	2	77.53^a ɤ	65.91^b α	66.74^ab α β	67.74^ac β
	3	77.71^a β	66.38^b α	69.49^bc α	67.69^ac α
	4	81.30^b ɤ	66.94^b δ	70.24^c α	74.43^b β
	5	81.21^b ɤ	66.88^b β	67.29^abc α β	68.28^c α
Volume
(mm^3)	1	6110.91^a β	9667.20^a ɤ	5489.13^a α	6399.57^a β
	2	4552.59^b ɤ	6202.62^b δ	5795.85^ab α	5050.75^cd β
	3	4613.82^b ɤ	7489.45^c β	5920.93^b α	7326.99^b β
	4	6143.98^a ɤ	6673.16^d δ	4000.98^c α	4519.05^c β
	5	5034.34^c ɤ	6864.32^d β	5583.01^a α	5584.35^d β

Significant differences are shown by different letters (a–d) and (α–δ) (p < 0.05).

a,b,c,d are used for intra-varietal significant differences. α, β ɤ δ for inter-varietal significant differences.

Table 3. Kernel traits of four almond cultivars, Ferragnes, Ferraduel, Marcona and Fournat cultivated in five different zones [(1) Tancherfi; (2) Mechraa Hammadi; (3) Sidi Bouhria; (4) Rislane; (5) Bsara] of North Eastern Morocco. Intra and inter-varietal, significant differences are, respectively, shown by letters (a–d) and (α–δ) (p < 0.05).

Parameters	Zone	Marcona	Fournat	Ferragnes	Ferraduel
Weight
(g)	1	0.86^a ɤ	1.38^a δ	1,05^ab α	0.95^a β
	2	0.73^b ɤ	1.01^b δ	1,19^c α	0.83^b β
	3	0.74^b ɤ	1.16^c δ	1,02^a α	0.94^a β
	4	0.90^a β	1.06^b ɤ	0,88^d α β	0.82^b α
	5	0.76^b β	1.02^b α	1,09^b α	0.85^b β
Width
(mm)	1	14.81^a β	16.06^a ɤ	13,63^a α	14.83^a β
	2	13.20^b β	14.66^b ɤ	13,82^ab α	13.48^b α β
	3	13.38^b ɤ	15.33^c β	14,42^b α	14.57^a α β
	4	14.78^a β	14.84^b β	12,39^c α	12.41^c α
	5	13.25^b β	14.60^b ɤ	13,82a^b α	13.52^b α β
Length
(mm)	1	19.37^a ɤ	28.80^a δ	25,12^a α	24.21^a β
	2	17.92^b ɤ	25.71^bc δ	25,06^a α	22.01^b β
	3	18.43^c β	26.22^b ɤ	23,55^b α	23.33^c α
	4	19.00^a β	25.29^c ɤ	21,36^c α	21.12^d α
	5	17.79^b ɤ	25.64^bc δ	24,20^d α	21.58^b β
Thickness
(mm)	1	6.94^a ɤ	6.35^a β	7,19^a α	6.56^ac β
	2	6.79^a ɤ	6.10^bc δ	8,17^b α	6.51^ac β
	3	7.23^b ɤ	6.53^ab β	7,60^c α	6.65^a β
	4	7.29^b β	6.23^bc ɤ	7,83^c α	7.01^b β
	5	7.30^b α	6.06^c β	7,56^c α	6.33^c β
Geometric diameter
(mm)	1	12.57^a β	14.31^a ɤ	13,5^a α	13.29^a α
	2	11.71^b ɤ	13.19^b δ	14,13^b α	12.44^b β
	3	12.11^c ɤ	13.79^c α	13,67^a α	13.11^a β
	4	12.68^a α	13.26^c ɤ	12,7^c α	12.23^b β
	5	11.97^c β	13.13^c ɤ	13,61^a α	12.48^b β
Sphericity
(%)	1	64.95^a ɤ	49.72^a δ	53,77^a α	54.96^a β
	2	65.35^a β	51.34^b ɤ	56,42^b α	56.62^b α
	3	65.79^ab ɤ	52.61^c δ	58,1^c α	56.25^b β
	4	66.81^bc ɤ	52.45^c δ	59,53^d α	57.97^c β
	5	67.35^c β	51.26^b ɤ	56,27^b α	56.78^b α
Volume
(mm^3)	1	1044.45^a β	1553.01^a ɤ	1293,03^a α	1237.74^a α
	2	0846.09^b ɤ	1209.82^b δ	1484,64^b α	1014.30^b β
	3	0935.16^c ɤ	1378.01^c α	1354,51^a α	1185.18^a β
	4	1071.46^a α	1234.25^b ɤ	1084,97^c α	0962.35^b β
	5	0904.96^bc β	1191.10^b ɤ	1329,27^a α	0963.78^b β
Shelling
(%)	1	20.27^a ɤ	30.64^a α	29,8^a α	22.52^a β
	2	23.58^b ɤ	33.19^c β	32,34^b α β	30.83^b α
	3	23.54^b ɤ	32.88^bc δ	30,21^a α	25.62^c β
	4	23.42^b ɤ	32.35^ab α	33,54^c α	25.45^b β
	5	22.03^c α	30.97^ab β	32,75^bc α	30.04^b β
Double kernels rate (%)	1	0	0	0	0
	2	0	0	0	0
	3	0	7	12	15
	4	0	0	0	15
	5	0	0	0	0

The mean values of calculated parameters from mathematical equations such as nuts sphericity (φ) and volume (V) showed that Fournat cultivar had the lowest sphericity (64.15%) but the highest volume (9667.20 mm³) in Tancherfi, while in Rislane, Marcona had the highest sphericity (81.30%) and Ferragnes showed the lowest volume (4000.98 mm³). Concerning the geometric diameter (Dg), Ferragnes’ nuts had a lowest value (19.66 mm) in Rislane whereas Fournat’s nuts had the highest Dg (26.38 mm) in Tancherfi. According to these results, among the studied almond tree cultivars, Fournat and the couple Ferragnes/Ferraduel show a good almond yield potential (good shelling percentage and no double kernels) in three zones (Tancherfi, Mechraa Hammadi and Bsara). These zones could be considered as suitable areas for almond tree growing.

As reported by Ak et al. (2005; Colic et al., 2012), high variations of nuts traits were observed; however, certain of them seem to be cultivar dependent, that is, the case of nuts sphericity for Marcona, which presents the highest values for almond nuts sphericity in the five studied zones. In contrast, Fournat cultivar is characterized by low nuts sphericity and has the highest mean values for volume and length of nuts in the five zones of this study. Almond shells for the fourth cultivars are generally characterized by a cracking resistance, which plays an important role for kernel protection during manipulation and processing (Kodad et al., 2015) and also protects kernel from bird and rodent attacks as well as it presents low kernel sensibility to navel orange worm (NOW) and carcinogenic aflatoxins-producing fungi.

The kernel is the edible part of the nut with a high nutritional value. Kernel large size is commercially important (Socias I Compagny et al., 2010). The dimensions of almond kernels were determined for the four almond cultivars. All of them produce small-to-medium kernels. Kernel size depends on kernel weight. According to “Almonds descriptors” (Gülcan, 1985), kernel’s weights of the studied cultivars vary between small size kernels of 0.73 g for Marcona in Machraa Hammadi to medium size kernels of 1.38 g for Fournat in Tancherfi. These regions are known by an arid climate and long drought seasons which can explain the small fruit size for the four studied almond cultivars. In Rislane zone, Ferragnes shows the lowest width (12.39 mm) but Fournat presents the highest one (16.06 mm) in Tancherfi. In Bsara zone, Marcona cultivar produces the smallest kernels with the lowest length value of 17.79 mm, whereas Fournat in Tancherfi produces the largest kernels (length value of 28.80 mm).

Kernel thickness for these introduced cultivars scaled between 6.06 mm recorded for Fournat in Bsara, and 8.17 mm for Ferragnes in Mechraa Hammadi. According to the almond descriptors (Gülcan, 1985), we conclude that fruits of the fourth almond cultivars had thin-to-thick kernels. The nut sizes for the couple F/F are quite similar for length and lower for weight and thickness than those reported by Naska et al. (2005).

Statistical analysis of pomological traits on kernels of the four almond cultivars shows that Fournat is characterized by the highest values of kernel’s width and length in the five zones of this study and generally by a high kernels weight in all these zones. The highest value for kernels weight (1.38 g) has been recorded in zone 1 “Tancherfi” (Table 3). Ferragnes almond kernels are characterized by high values for kernel’s thickness in the five zones; the highest value (8.17 mm) have been observed in zone 2 “Mechraa Hammadi”. In addition, kernel’s geometrical diameter (Dg) ranges from 11.71 mm, for Marcona in zone 2, up to 14.31 mm, for Fournat in zone 1. Sphericity scaled from 49.72%, for Fournat in Tancherfi up to 67.35% for Marcona in zone 5 “Bsara”. The highest kernel’s volume 1553.01 mm³ was recorded for Fournat in zone1 “Tancherfi”, followed by Ferragnes (1484.64 mm³) in zone 2 “Mechraa Hammadi”, but the lowest kernel’s volume (846.09 mm³) was registered for Marcona in “Mechraa Hammadi”.

Shelling percentage and double kernels rate, which are two important commercial parameters, were also estimated. Ferragnes showed the best shelling percentage (33.54%) in zone 4 “Rislane” while low shelling percentage values have been observed for Marcona in all the studied zones with the lowest value (20.27%) in zone 1 “Tancherfi”. The rate of double kernel, which is considered as negative commercial parameter for international standardized trade, was observed in zone 3 “Sidi Bouhria” and zone 4 “Rislane” with rates of 7% to 15%, respectively. Its concerns the couple F/F and Fournat cultivars and probably related to the type of rootstock. In other pomological studies, carried out on F/F cultivars, data showed a double kernel rate less than 1% (Monastra et al., 1984); however; Ak et al. (2005) found for Ferraduel cultivar a double kernel rate of 20%. The origin of this percentage in both zones could be related to the bitter almond rootstock used in place of Marcona rootstock. This hypothesis was confirmed by tasting tests which showed the presence of bitter almond in some samples collected in these zones. The bitter almond characterizes more often the local germplasm which is distinguished by a high rate of double kernel (Kodad et al., 2015).

Comparing the two cultivars Ferragnes and Ferraduel, we observed that Ferragnes is characterized by high value of weight, length, thickness, volume and shelling percentage in the all studied sites (Table 3). Our results are comparable to those reported by Hanine et al. (2014) in a similar study of almond pomology in other zones of Morocco, but different in weights kernels and slightly lower than the results reported for these cultivars in their original site, as described by Monastra et al. (1984).

Pomological traits on nut or kernel statistical analyses allow us to distinguish between the studied almonds cultivars. Thus, Marcona is characterized by its high sphericity, and Fournat is characterized by the high weight, the width and the length of its nuts. Ferragnes is characterized by high thickness of kernels and a high shelling percentage compared to Ferraduel.

Conclusion

The present study concerns the assessment of nuts and kernels physical traits of four almond cultivars recently introduced in eastern Morocco. The aim is to identify the best cultivars, which best adapted to the climatic conditions of different sites favorable for the cultivation of almonds in this region. Our result shows a large variability of pomological characters among studied almond cultivars and their performances are different. Thus, each cultivar is distinguished by one or more morphological parameters (e.g., Marcona by sphericity, Fournat by length…). Moreover, all examined cultivars are pretty well adapted to the environmental conditions of this region and produce almonds in the five geographical localizations studied with some profitable areas as “Tancherfi site” for kernel weight or “Rislane” for shelling percentage. The target is to grow late flowering productive cultivar, suitable for the dry climate conditions and to the markets demands. Thus, it can be assumed that at least Ferragnes Ferraduel and Fournat cultivars could be recommended for this region. However, Marcona cultivar, which seems to be less resistant to drought or to reduce water conditions, presents weak nut and kernel trait values.