Influence of Scion and Rootstock on Incidence of Peach Tree Short Life

Previous work has suggested that peach scion cultivar exerts a significant influence on incidence of peach tree short life (PTSL) in trees budded onto Nemaguard and Flordaguard seedling peach rootstocks. If this influence is consistent across a range of rootstocks then the influence of scion cultivar might offer a new tool for the management of PTSL. Growers could minimize losses on those sites most prone to PTSL by using the least susceptible scion/rootstock combinations. In this trial trees of ‘Agua 6-4,’ ‘Springcrest,’ ‘Redglobe,’ ‘Redhaven’ and ‘Cresthaven’ budded onto Guardian (BY520-9), Lovell, Nemaguard and Siberian C peach seedling rootstocks were planted on a site with a known history of PTSL. After 6 years, 31 % of test trees had succumbed to PTSL and 18% to other causes. Both scion and rootstock exerted a profound influence on incidence of PTSL (P<0.0001). Mean effects of scion cultivar ranged from 10 to 49% PTSL mortality. Mean effects of rootstock treatment ranged from 10 to 85% PTSL mortality. However, a significant scion x rootstock interaction was also present (P<0.05). This appeared to be largely the result of anomalously low or high PTSL incidence observed in 2 scion/rootstock combinations. These results suggest that some caution should be used in extrapolating the rootstock treatment effects determined in a typical PTSL trial budded with a single scion cultivar to their influence beneath other untested scion cultivars. INTRODUCTION Peach [Prunus persica (L.) Batsch] trees appear to be predisposed to peach tree short life (PTSL) by the ring nematode [Mesocriconema xenoplax (Raski) Loof & deGrisse] (Nyczepir et al., 1983). However, the actual cause of death is suspected to be either cold injury or bacterial canker (Pseudomonas syringae pv syringae van Hall) of the scion (Ritchie et al., 1981). Rootstocks have been identified which either enhance or reduce incidence of PTSL (Okie et al., 1994; Yadava et al., 1989; Dozier et al., 1984). Very little is known about the effect of the scion cultivar on susceptibility of a scion/rootstock combination to PTSL.Most PTSL trials reported to date have tested a range of rootstocks budded with only a single scion cultivar and only occasionally with more (Reighard et al., 1997; Yadava et al., 1989; and Dozier et al., 1984). One recent report (Beckman et al., 1994) utilizing a wide range of scion cultivars budded to Nemaguard seedling rootstock demonstrated a significant scion influence on incidence of PTSL.Another report (Sherman et al., 1994) showed high PTSL variability in peach scion genotypes budded on Flordaguard seedling rootstock.These reports suggest that scion cultivar exerted an influence equal to, if not greater, than that typically attributed to rootstock on incidence of PTSL. If this effect proved to be uniform across a range of rootstocks, then it would offer growers a new tool for managing PTSL, i.e. the use of the most resistant scion cultivars in conjunction with the most resistant rootstocks on severe PTSL sites. The purpose of this trial was to determine the influence of scion and rootstock genotype on susceptibility to PTSL.