Propagação vegetativa de seleções de porta-enxertos potencialmente tolerantes à morte-precoce do pessegueiro

Abstract

A morte-precoce do pessegueiro é uma síndrome cuja causa envolve diversos agentes bióticos e abióticos e, para reduzir os prejuízos, a principal linha de pesquisa tem sido a busca por porta-enxertos tolerantes. Dentre as características desejáveis em um bom porta-enxerto, a facilidade de propagação vegetativa é fundamental para preservação da identidade genética e facilitar a difusão de tecnologias. O objetivo, com o presente trabalho, foi avaliar a viabilidade técnica da propagação vegetativa por estacas herbáceas de 18 seleções clonais de porta-enxertos [Prunus persica (L.) Batsch.] potencialmente tolerantes à morte-precoce, sob câmara de nebulização intermitente. Como cultivares de referência, foram utilizadas 'Capdeboscq', 'Okinawa' (P. persica) e 'Sharpe' ['Chickasaw' (Prunus angustifolia Marsh.) x Prunus spp.]. Com as avaliações realizadas após 65 dias da estaquia, foi possível concluir que a propagação das seleções de porta-enxertos por estacas herbáceas é tecnicamente viável, com porcentagens de enraizamento que variaram de 21,67% a 91,67%, de tal forma que nenhum desses genótipos deve ser descartado do processo de seleção. A qualidade das raízes adventícias formadas foi satisfatória na maioria dos genótipos estudados, com elevadas porcentagens de estacas aptas ao transplantio, satisfatório número e comprimento de raízes. Entretanto, a seleção WFM-ESM-07-04 e as cultivares Capdeboscq e Sharpe se destacaram positivamente nesse aspecto. Dentre os três portaenxertos de referência utilizados, 'Okinawa' e 'Capdeboscq' apresentaram capacidade propagativa (rendimento) por estacas herbáceas bastante similar entre si, porém ambos são melhores do que 'Sharpe'.

Production of self-rooted peach seedlings

“…In a study conducted on the rooting of 'Okinawa' peach tree herbaceous mini-cuttings collected from young plants, the best results were obtained with the use of fine or average granulometry vermiculite (87,6% e 80,6%, respectively), attributed to the best water/ air balance presented by the vermiculite (Nachtigal and Pereira 2000). These rooting percentages agree with those reported by Mayer et al (2009), who obtained from some peach tree genotypes up to 87% of rooted cuttings ready to be transplanted.…”

Adventitious rooting of cultivars and clonal selections of Prunus spp. rootstock under intermittent mist system

“…Softwood cuttings without their original leaves do not perform photosynthesis and do not produce cofactors essential to rooting and, with the high summer air temperatures and without having started the rhizogenesis, they die early (Machida et al, 1977;Hartmann et al, 2002;Thomas & Schiefelbein, 2004;Santoro et al, 2010;Tombesi et al 2015;Sanchez et al, 2020). Leaves are essential for softwood cuttings of peach and several other species (Hartmann et al, 2002;Thomas & Schiefelbein, 2004;Santoro et al, 2010;Mayer et al, 2014b;Mayer et al, 2015a;Tombesi et al 2015;Mayer et al, 2018). There are several factors that can contribute to the early original leaf fall on cuttings under intermittent mist system, such as the deficient nutrition of mother tree, inappropriate shoots for cutting preparation (date, type, age, size, diameter, health, etc...), endogenous hormonal balance favorable to leaf senescence, genetics, leaf and petiole morphology, water stress (from the air and/or substrate), inadequate regulation of mist system, thermal stress (especially air temperature differences between day and night), fungal diseases, and inappropriate containers and/ or substrates (Hartmann et al, 2002;Osterc et al, 2009;Osterc & Štampar, 2011;Neèas & Krška, 2013;Ruter, 2015;Fragoso et al, 2015;Mayer et al, 2015a;Mayer et al, 2020).…”

“…The cutting base was immersed in a hydroalcoholic solution at 50% (hydrated ethyl alcohol 96° GL + distilled water) of 4, 3 -indolylbutyric acid -IBA (C 12 H 13 NO 2 , purity >98%, Vetec ® ) at 3,000mg.L -1 by fast immersion of 5 seconds (Figure 1d.) (Hartmann et al, 2002;Mayer et al, 2018;Mayer et al, 2020). Trial 2 was set up on 13 th and 14 th , January/ 2019, with same methodology adopted in trial 1.…”

“…Intermittent mist system was programmed by a timer to be activated for 10 seconds each 5 minutes, in the first 20 days of each trial, which allowed maintenance of constant moist on leaf surface (Ruter, 2015;Mayer et al, 2018;Mayer et al, 2020). In the following days, off-period was gradually increased at night until 45 th and, after that, completely turned-off at night.…”

“…The percentages of live rooted cuttings in both trials (Tables 2 and 4) were considered satisfactory. The percentage of live rooted cuttings is the key in cutting propagation trials (Hartmann et al, 2002;Mayer et al, 2018;Mayer et al, 2020). The highest values observed in 10 selections (trial 2, Table 4) and statistical equality of three selections (trial 1, Table 2), in relation to the reference cultivars, reveals that selected clones also present satisfactory rooting ability, besides potentially tolerant to the PTSL syndrome.…”