Stability of bacterial leaf spot resistance in peach regenerants under in vitro, greenhouse and field conditions

Abstract

Phenotypic stability of bacterial leaf spot resistance in peach (Prunus persica (L.) Batsch) regenerants, either selected at the cellular level for insensitivity to a toxic culture filtrate of Xanthomonas campestris pv . pruni or screened at the whole plant level for resistance to X. campestris pv. pruni, was investigated. A detached-leaf bioassay was used to evaluate the original regenerants again after three years in the greenhouse and also after a two to three year cycle of tissue culture propagation . Peach trees derived through micropropagation from the original regenerants were also evaluated after one to three years growth in the field . Although leaf spot resistance was retained in some regenerants over time in the greenhouse, following in vitro propagation, and under field conditions, resistance was either lost or not expressed in others . Regenerants # 19-1 and #156-6, derived from embryo callus of bacterial spot susceptible `Sunhigh', were significantly more resistant than `Sunhigh' . High levels of resistance were exhibited in greenhouse plants and field-grown trees of regenerant # 122-1, derived from embryo callus of moderately resistant 'Redhaven' . This research provides additional evidence that selecting or screening for somaclonal variants with disease resistance is a feasible approach to obtaining peach trees with increased levels of bacterial spot resistance .

Disease response of carrot and carrot somaclones to Alternaria dauci

“…The reduction or instability of the somaclonal variation in the seed generation is less of a problem with perennials that rely on vegetative propagation for multiplication. Here the incidence of disease resistance in somaclones has been very encouraging (Ostry & Skilling, 1988;Prakash & Thielges, 1989;Hammerschlag et al, 1994).…”

“…lycopersici was achieved by exposing tomato protoclones in vitro to a nonspecific toxin (Shahin & Spivey, 1986). Somaclones of peach selected in vitro were also found to show increased resistance to bacterial leaf spot (Hammerschlag et al, 1994) and somaclones of celery selected in vitro showed heritable resistance to Fusarium oxysporum f.sp. apii (Heath-Pagliuso et al, 1988).…”

In vitro response of strawberry cultivars and regenerants to Colletotrichum acutatum

“…Hammerschlag (1990) reported that 33-100% of peach regenerants (maintained under greenhouse conditions, but leaves assayed in vitro) were either significantly more resistant or susceptible to Xanthomonas campestris pv. pruni compared with the parent cultivar; however, only one regenerant retained increased levels of disease resistance under field conditions and had heritable resistance (Hammerschlag et al, 1994;Hammerschlag, 2000). In the present study, 15-21 regenerants per cultivar were evaluated, and the percentage of somaclonal variants with significantly higher levels of resistance to C. acutatum ranged from 25% for cultivar Honeoye to 100% for cultivars Chandler and Delmarvel (Table 1).…”

“…These same observations were reported for peach in response to X. campestris pv. pruni (Hammerschlag et al, 1994).…”

“…(Barden et al, 1986), apple (Malus x domestica Borkh.) (Donovan et al, 1994), and peach (Prunus persica L. Batsch) (Hammerschlag, 1990(Hammerschlag, , 1994(Hammerschlag, , 2000. This approach has also generated strawberry somaclones with increased resistance to Fusarium oxysporum f. sp.…”