405 PRELIMINARY RESULTS ON THE EFFECTS OF DIFFERENT PISTACIA SPECIES POLLEN ON FRUIT CHARACTERISTICS OF TWO COMMERCIAL CULTIVARS ‘MATEUR’ AND ‘EL GUETTAR’ H. Gouta, A.Chelli Chaabouni, M. Ghrab I. Ben Aïssa, M. Ben Mimoun, R. Hellali Olive Tree Institute National Agronomic Institute of Tunisia Route de l’Aéroport Km 1.5 42, Avenue Charles Nicole BP. 1087. 3016 Sfax 1082 Cite Mahrajène Tunisia Tunisia Keywords: pistachio, pollen, P. vera, P. atlantica, P. terebinthus. Abstract The effects of the pollen parent (xenia) on seed and fruit characters are known to occur in several nut crops. For pistachio this phenomenon is under discussion. In this experiment, effects of Pistacia vera, P. atlantica and P. terebinthus pollen on fruit size and weight of two commercially grown cultivars (P. vera cvs. 'Mateur' and 'El Guettar') were tested and compared to an open-pollinated control. For the two cultivars it was concluded that fruits obtained by pollination with P. atlantica pollen, were better than those resulting from pollination by other Pistacia species and a significant difference was noted for some parameters measured. In contrast, no effects of the different pollinators were observed for kernel weight. For 'Mateur' the percentage of blank fruits was lower (6.76%) under open pollination, while for 'El Guettar' the use of P. terebinthus pollen gave the lowest percentage (19.46%). 1. Introduction The main species of the genus Pistacia in Tunisia are P. atlantica Desf., P. lentiscus L., P. terebinthus and P. vera L. Among these species only P. vera has edible nuts and commercial importance. While it is a dioecious tree, pollination is very important to obtain a high yield. The effects of the pollen parent (xenia) on seed and fruit characters are known to occur in several nut crops: almond (Crane and Lawrence, 1956; Kumar and Das, 1996), chestnut (McKay and Crane, 1939), and pecan (Romberg and Smith, 1946; Marquard, 1988). For pistachio a good deal of research has been done on the effect of the pollen parent on fruit quality traits (Peebles and Hope, 1937; Whitehouse et al., 1964; Crane and Iwaki, 1980; Riazi et al., 1996). Whitehouse et al. (1964) reported that kernel weight of nuts pollinated with P. atlantica was not significantly lower than those with P. vera for the 'Trabonella' and 'Bronte' cultivars. Crane and Iwakiri (1980) concluded that none of the various pollen sources altered overall fruit size and percent blanks. Length and dry weight of kernels were affected by cross-pollination with P. atlantica pollen. Ak (1998) reported that the fruits pollinated with P. vera pollen were better than those resulting from pollination by other Pistacia species. The works cited concerned different commercial cultivars but until now no studies have been conducted on the Tunisian cultivars. This work studies the effect of different pollen parents on fruit dimensions and weight of 'Mateur' and 'El Guettar', which are the leading cultivars commercially grown in Tunisia. 2. Materials and methods This work was carried out during the year 2000 in the pistachio collection of the Proc. 3 rd IS on Pistachios and Almonds Eds. I. Battle, I. Hormaza & M.T. Espiau Acta Hort. 591, ISHS 2002