Genetic diversity of almond ( Prunus amygdalus Batsch) in Tunisia: a morphological traits analysis.

摘要

In Tunisia, the almond tree (Prunus amygdalus Batsch) dates back to ancient times and has been known since the Carthaginian era. About 90% of the almond production is in the semi-arid central and southern part of the country. In the north, Bizerte presents a very specific ecosystem, with cultivars practically resistant to strong wind and high humidity. Due to recent severe drought, more than three million trees were lost. This has resulted in a strong decline of the local almond gene pool and a real risk of losing useful genetic resources for breeding programs and other uses. To safeguard the remaining almond germplasm, collecting of traditional almond cultivation areas has taken place in the past few years. More than 70 ecotypes have been identified and characterized. For this study, 50 almond cultivars and ecotypes were screened using 27 morphological and pomological traits. Principal Component Analysis shows that the first three principal components retained explain more than 41% of the total variance. The main fruit weight and size variables such as nut weight, nut length, nut thickness, nut size, kernel length, kernel weight, and kernel thickness were strongly associated with the first principal component. Percentages of double kernel and aborted kernel were positively associated with the second principal component. As the shelling percentage was negatively associated with the third principal component, this last was considered a component of commercial value. Cluster analysis classifies the studied almond cultivars into six groups.