H. Gouta¹, E. Ksia², M.M. Ayachi¹ and P. Martínez-Gómez^3
1 Olive Tree Institute, Sfax, Tunisia
² Laboratoire de Biologie des Plantes et Biotechnologies, Faculté des Sciences, Campus Universitaire, El Manar, Tunis, Tunisia
³ Department of Plant Breeding, CEBAS-CSIC, Espinardo, Murcia, Spain

SUMMARY Almonds have been cultivated in Tunisia since ancient times. Due to increasingly severe dry condi­tions, the local almond gene pool has significantly decreased since the 1980’s. In order to rescue the remaining almond germplasm and to investigate the existing agronomical variation in Tunisia, a survey was undertaken several years ago to identify and pre­serve the traditional almond cultivars. In this study, 52 local almond cultivars and ecotypes were evaluat­ed for three consecutive years, and 18 different tree, kernel and nut traits were observed. Results show a great diversity of almond ecotypes and cultivars in Tunisia. Kernel weight and size and adaptation to dry conditions are the most interesting qualities of this local germplasm. However, self-incompatibility, early flowering and the presence of double kernels are the most common obstacles for using this germplasm in breeding. Furthermore, principal component analy­sis was used to identify morphological variation pat­terns and to classify the genotypes. In this analysis, the first three retained principal components were found to explain more than 56% of the total variance. The main nut traits, such as length, thickness and size, were strongly associated with the first principal component. However, shell retention, shelling per­centage and kernel weight had the highest loadings for the second principal component. Finally, cluster analysis revealed four groups for the almond culti­vars studied, but no discrimination among genotypes according to their origin was observed. Results show the great pomological variation of local Tunisian al­mond cultivars and their breeding value for increas­ing Tunisian almond production and as source of drought resistance. Keywords Prunus, almond local ecotypes, breeding, germplasm, drought resistance, agronomical diversity

Significance of this study What is already known on this subject? The rich Tunisian almond germplasm evaluated through molecular markers. What are the new findings? The agronomical evaluation of the rich Tunisian almond germplasm under local drought conditions. What is the expected impact on horticulture? The breeding possibilities of this rich Tunisian almond germplasm and the prospects for new productive with higher quality almond releases adapted to drought conditions.

E-mail: pmartinez@cebas.csic.es  

References

• Ak, B.E., Kuzdere, H., and Kaska, N. (2005). An investigation on phenological and pomological traits of some almond cultivars grown at Ceylanpinar State farm in Turkey. Options Méditerr. 63, 43–48.

• Artega, N., and Socias i Company, R. (2001). Heritability of fruit and kernel traits in almond. Acta Hortic. 591, 269–274.

• Badenes, M.L., Martínez-Calvo, J., and Lacer, G. (1998). Analysis of apricot germplasm from the European ecogeographical group. Euphytica 102, 93–99. https://doi.org/10.1023/A:1018332312570.

• Chalak, L., Chehade, A., and Kadri, A. (2007). Morphological characterization of cultivated almonds in Lebanon. Fruits 62, 177– 186. https://doi.org/10.1051/fruits:2007013.

• Colic, S., Rakonjac, V., Zec, G., Nocolic, D., and Fotiric Aksic, M. (2012). Morphological and biochemical evaluation of selected almond [Prunus dulcis (Mill.) D.A. Webb] genotypes in northern Serbia. Turk. J. Agri. For. 36, 429–438.

• De Giorgio, D., Leo, G., Zacheo, G., and Lamascese, N. (2007). Evaluation of 52 almond cultivars from the Apulia region in Southern Italy. J. Hortic. Sci. Biotechnol. 82, 541–546. https://doi.org/10.1080/14620316.2007.11512271.

• Dicenta, F., García, J.E., and Carbonell, E.A. (1993). Heritability of flowering, productivity and maturity in almond. J. Hortic. Sci. 68, 113–120. https://doi.org/10.1080/00221589.1993.11516334.

• Egea, J., and Burgos, L. (1995). Double kernelled fruits in almond (Prunus dulcis Mill.) as related to pre-blossom temperature. Ann. Appl. Biol. 126, 163–168. https://doi.org/10.1111/j.1744-7348.1995.tb05012.x.

• Egea, G., Nortes, P.A., González-Real, M.M., Baille, A., and Domingo, A. (2010). Agronomic response and water productivity of almond trees under contrasted deficit irrigation regimes. Agric. Water Manag. 97, 171–181. https://doi.org/10.1016/j.agwat.2009.09.006.

• Fathi, A., Ghareyazi, B., Haghnazari, A., Ghaffari, M.R., Pirseyedi, S.M., Kadkhodaei, S., Naghavi, M.R., and Mardi, M. (2008). Assessment of the genetic diversity of almond (Prunus dulcis) using microsatellite markers and morphological traits. Iran J. Biotechnol. 6, 98–106.

• García, M.C., González-García, E., Vásquez-Villanueva, R., and Marina, M.L. (2016). Apricot and other seeds stones: amygnalin content and the potential to obtain antioxidant, angiotensin I converting enzyme inhibitor and hypocholesterolemic peptides. Food Funct. 7, 4693. https://doi.org/10.1039/C6FO01132B.

• Gouta, H., Ksia, E., Zoghlami, N., Zarrouk, M., and Mliki, A. (2008). Genetic diversity and phylogenetic relationships among Tunisian almond cultivars revealed by RAPD markers. J. Hort. Sci. Biotechnol. 83, 707–712. https://doi.org/10.1080/14620316.2008.11512448.

• Gouta, H., Guenichi, H., Rezgui, R., Mars, M., Zarrouk, M., and Mliki, A. (2010). Systèmes de production et ressources génétique de l’amandier (Prunus dulcis L.) dans le Centre-West Tunisien. Revue des Régions Arides 24, 106–111.

• Gouta, H., Mares, M., Gouiaa, M., Ghrab, M., Zarrouk, M., and Mliki, A. (2011). Genetic diversity of almond (Prunus amygdalus Batsch.) in Tunisia: A morphological traits analysis. Acta Hortic. 912, 351–358. https://doi.org/10.17660/ActaHortic.2011.912.51.

• Gouta, H., Ksia, E., Buhner-Zaharieva, T., Mliki, A., and Gogorcena, Y. (2012). Development of an SSR-based identification key for Tunisian local almonds. Sci. Agric. 69, 108–113. https://doi.org/10.1590/S0103-90162012000200004.

• Gradziel, T.M., and Kester, D.E. (1998). Breeding for self-fertility in California almond cultivars. Acta Hortic. 470, 109–117. https://doi.org/10.17660/ActaHortic.1998.470.15.

• Gradziel, T.M., and Martínez-Gómez, P. (2002). Shell seal breakdown in almond is associated with the site of secondary ovule abortion. J. Am. Soc. Hortic. Sci. 127, 69–74. https://doi.org/10.21273/JASHS.127.1.69.

• Gradziel, T.M., and Martínez-Gómez, P. (2013). Almond breeding. Plant Breed. Rev. 37, 207–259. https://doi.org/10.1002/9781118497869.ch4.

• Gradziel, T.M., Martínez-Gómez, P., Dicenta, F., and Kester, D.E. (2001). The utilization of Prunus species for almond variety improvement. J. Am. Pomol. Soc. 55, 100–108.

• Gradziel, T.M., Kester, D.E., and Martínez-Gómez, P. (2002). A development based classification for branch architecture in almond. J. Am. Pomol. Soc. 56, 106–112.

• Grasselly, Ch., and Crossa-Raynaud, P. (1980). L’amandier (Paris, France: Eds. Maisonneuve et Larose).

• Hjalmarsson, I., and Ortiz, R. (2000). In situ and ex situ assessment of morphological and fruit variation in Scandinavian sweet cherry. Sci. Hortic. 85, 37–49. https://doi.org/10.1016/S0304-4238(99)00123-5.

• Kester, D.E., Micke, W.C., Rough, D., Morrison, D., and Curtis, R. (1980). Almond variety evaluation. California Agric. 34, 4–7.

• Krahl, K.H., Lansari, A., and Iezzoni, A.F. (1991). Morphological variation within a sour cherry collection. Euphytica 52, 47–55.

• Lansari, A., Iezzoni, A.F., and Kester, D.E. (1994). Morphological variations within collections of Moroccan almond clones and Mediterranean and North American cultivars. Euphytica 78, 27–41.

• Ledbetter, C.A., and Shannard, C.B. (1992). Evaluation of selected almond (Prunus dulcis (Miller) D.A. Webb) germplasm for several shell and kernel characteristics. Fruit Var. J. 46, 79–82.

• Miarnau, X., Montserrat, R., Battle, I., and Vargas, F.J. (2013). High density planting in almond orchards. VI Int. Symp. on Almonds and Pistachios, Murcia (Spain), May 2013.

• Musa-Velasco, K., Paulionis, L., Poon, T., and Lee, H.Y. (2016). The effect of almond consumption on fasting blood lipid levels: a systematic review and meta-analysis of randomised controlled trials. J. Nutr. Sci. 5, e34. https://doi.org/10.1017/jns.2016.19.

• Nikolic, D., Rakonjac, V., Milatovic, D., and Fotiric, M. (2010). Multivariate analysis of vineyard peach [Prunus persica (L.) Batsch.] germplasm collection. Euphytica 171, 227–234. https://doi.org/10.1007/s10681-009-0032-3.

• Poonam, V., Raunak, G., Kumar, C.S., Reddy, L., Jain, R., Sharma, S.K., Prasad, A.K., and Parmar, V.S. (2011). Chemical constituents of the genus Prunus and their medical properties. Curr. Med. Chem. 18, 3758–3824. https://doi.org/10.2174/092986711803414386.

• Rius, X., Bordas, M., and Torrents, J. (2013). Super high density almond orchards. VI Int. Symp. on Almonds and Pistachios, Murcia (Spain), 27–31 May.

• Rohlf, J.F. (2004). NTSYS-pc: 2.11 Numerical Taxonomy and Multivariate Analysis System (New York, USA: Exeter Software).

• Sánchez Pérez, R., Ortega, E., Dual, H., Martínez-Gómez, P., and Dicenta, F. (2007). Inheritance and relationships of important agronomic traits in almond. Euphytica 155, 381–391. https://doi.org/10.1007/s10681-006-9339-5.

• Sorkheh, K., Shiran, B., Gradziel, T.M., Epperson, B.K., Martínez-Gómez, P., and Asadi, E. (2007). Amplified fragment length polymorphism as a tool for molecular characterization of almond germplasm: genetic diversity among cultivated genotypes and related wild species of almond, and its relationships with agronomic traits. Euphytica 156, 327–344. https://doi.org/10.1007/s10681-007-9382-x.

• Sorkheh, K., Shiran, B., Rouhi, V., Asadi, E., Jahanbazi, H., Moradi, H., Gradziel, T.M., and Martínez-Gómez, P. (2009). Phenotypic diversity within native Iranian almond (Prunus spp.) species and their breeding potential. Genet. Res. Crop Evol. 56, 947–961. https://doi.org/10.1007/s10722-009-9413-7.

• Sorkheh, K., Shiran, B., Khodambashi, M., Moradi, H., Gradziel, T.M., and Martínez-Gómez, P. (2010). Correlations between quantitative tree and fruit almond traits and their implications for breeding. Sci. Hortic. 125, 323–331. https://doi.org/10.1016/j.scienta.2010.04.014.

• Talhouk, S.N., Lubani, R.T., Baalbaki, R., Zurayk, R., Al-Khatib, A., and Parmaksizian, L. (2000). Phenotypic diversity and morphological characterization of Amygdalus L. species in almond. Genet. Res. Crop Evol. 47, 93–104. https://doi.org/10.1023/A:1008763021129.

Received: 28 March 2017 | Accepted: 30 May 2017 | Published: 24 April 2019 | Available online: 24 April 2019