Morphological investigation of genetic diversity of pistachio (Pistacia vera) germplasm in arid land of Tunisia

Background and aims - Pistachio (Pistacia vera L.) is an interesting crop for arid areas, well adapted to marginal lands and to drought conditions. Traditional production areas of Tunisia harbour an interesting diversity of pistachio gerrnplasm. In order to identify and describe this diversity, a field study was conducted in the traditional pistachio production areas of El-Guetar and Sfax in 2004 and 2005. Material and Methods - A total of 256 female and male pistachio specimens were prospected and compared to the main commercial cultivar 'Mateur'. Flowering, tree habit, nut and seed characteristics were determined for 64 pistachio female land races from the El-Guetar oasis and 25 female land races from Sfax. Key results - Differences were observed among all the land races. Flowering and ripening time were particularly variable. Significant variation of nut weight from 0.48 to 1.03g was also observed. Some land races presented nut weight as much as 10% higher than 'Mateur' i.e. Fourati1 and Fourati10 from the region of Sfax and MTSG10, AMHA5 and EPE3 from the El-Guetar oasis. Blank production and split nuts ratio ranged respectively from 2 to 60% and from 14 to 95%. Furthermore, 20 land races had a blank production below 10% while 14 local land races had the split nuts ratio superior to 81% recorded for 'Mateur'. The phenotypic data were evaluated using cluster analysis. Parameters related to leaf and nut size and fruit quality had high discriminating values. Different groups of land races were identified with similar flowering periods, nut and seed characters for each cluster. Conclusion - The evaluation of gerrnplasm in Tunisia revealed promising land races. Additional biochemical and molecular studies will provide the necessary complementary information that could result in potentially valuable land race selection.