A NINE-YEAR STUDY ON THE PERFORMANCE OF TWELVE CHERRY ROOTSTOCKS UNDER NON-IRRIGATED CONDITIONS IN APULIA (SOUTHERN ITALY)

The spread of sweet cherry (Prunus avium L.) orchards in Apulia (southern Italy) mainly depends on the limited height of mature trees. Tree growth is controlled naturally as a consequence of several interrelated factors: poor and shallow soils, non-irrigated (rainfed) conditions, and the use of P. mahaleb Mill. 'St. Lucie' as the sole rootstock. The possibility of a further reduction of tree height by the use of rootstocks more dwarfing than P. mahaleb is intriguing; thus, a trial was conducted from 1996 throughout 2004 to determine the potential for such rootstocks. Self-compatible 'Lapins' was grafted onto the following 12 rootstocks: 'Mazzard', 'Mazzard F 12/1% 'CAB 6P', 'CAB HE', 'Weiroot® 158', 'Damil®' (GM 61/1), 'SL 64', 'Avima®-Argot', 'Delbard® MaxMa 14', 'Delbard® MaxMa 97', 'Colt' and 'Gisela® 5'. After nine years, only 15% of the trees on 'Gisela® 5' were alive, while the survival of trees on 'Avima®-Argot', 'CAB 11E' and 'MaxMa Delbard® 14' was more than 90%. The largest trunk cross-sectional area (TCSA) was recorded for 'Avima®-Argot', 'Colt' and 'SL 64'; the smallest TCSAs were on 'Damil®' and 'Weiroot® 158'. Significant suckering occurred with 'CAB 6P' and 'CAB 11E'. In 2004, the maximum tree height did not exceed 4.5 m on 'MaxMa 14'; only 'Weiroot® 158' produced trees smaller than 2.6 m. The earliest bearing rootstock was 'Weiroot® 158' (3rd leaf) and the latest was 'Mazzard F 12/1' (6th leaf). Cumulative 1998-2004 yields ranged from a minimum of 2.5 kg/tree ('Damil®') to a maximum of 45.5 kg/tree ('SL 64'). In terms of yield efficiency, the best results were on 'Weiroot® 158', 'SL 64' and 'Avima®-Argot'; the worst results were on 'Colt', 'MaxMa Delbard® 97', 'Mazzard', 'Mazzard F 12/1' and 'Damil®', in decreasing order. The overall results confirmed the satisfactory performance of 'SL 64' and the promising performance by dwarfing 'Weiroot® 158' and semi-dwarfing 'MaxMa 14'. 'Damil' and 'Gisela® 5' were totally unsuited to the local environment/growing conditions.