A method for adventitious shoot regeneration from leaves of micropropagated peach shoots has been developed. Apices were excised from in vitro shoot cultures of a seed-derived (juvenile) genotype (P16Cl5) and mature genotypes (Babygold 6, 842 Standard, San Giorgio and Yumyeong). Apices were cultured 21 days in the dark on a medium supplemented with 6-benzyladenine and α-naphthaleneacetic acid and then transferred to an auxin-free medium and incubated in the light for 21 days. The first four apical leaves were excised from these apices and cultured in the same way. During the dark incubation period, leaves developed a callus at the petiolar base. Adventitious shoots appeared on this callus after transfer to auxin-free medium and culture under light conditions. The morphogenic ability of the callus was maintained for several months.

During the production and assessment of transgenic plants resistant to quarantine viruses, the need to contain genetically modified plants (GMPs) and pathogens severely limits working options. Moreover, in the case of fruit trees, acclimatisation and viral inoculation are very time‐consuming, thus a quick and safe method to assess the resistance to quarantine viruses, such as Plum pox virus (PPV), is desirable. This article focuses on the production of transgenic plums together with a contained and rapid evaluation in vitro for PPV resistance. The plum ‘Stanley’ was transformed by Rhizobium radiobacter (syn. Agrobacterium tumefaciens) using a PPV‐M derived hairpin construct (h‐UTR/P1) that had previously been shown to confer high and broad‐spectrum PPV resistance in model plant. Two transgenic clones, St24 and St28, were obtained. To assess their ability to resist PPV infection, micropropagated shoots of the transgenic clones were micrografted in vitro onto PPV‐D infected ‘GF305’ rootstock. Following successful grafting, the transgenic scions were analysed by immunocapture‐reverse transcription‐polymerase chain reaction (IC‐RT‐PCR) for PPV detection. A total of 97% (47/48) of St24 and 73% (17/23) of St28 tested plants were resistant to the heterologous strain of PPV. In line with an RNA silencing mediated resistance mechanism, the St24 clone was shown to accumulate higher concentration of PPV UTR/P1‐specific small interfering RNAs (siRNAs) than St28 one. The results are of practical interest not only developing plum clones that are highly resistant to PPV, but also for setting up quick and contained inoculation test procedure.

No abstract

No abstract

No abstract