Propagation of New Chestnut Rootstocks with Improved Resistance to Phytophthora cinnamomi – New Cast Rootstocks

Abstract

Nowadays there is a great demand for chestnut rootstocks with improved resistance to Phytophthora cinnamomi, the causing agent of ink disease/root rot. The majority of genotypes that are being commercialized and used in the new plantations, were selected from the breeding programs of the XX century. The climate scenarios have been changing throughout the years, therefore the selection of new genotypes, better adapted to the current conditions of soil and climate, together with an effective and expedite production system, are essential to fulfill the needs of the market on better propagation materials. The INIAV’s chestnut breeding program, established in 2006, aims the improvement of resistance of chestnut to biotic stresses. By taking advantage of micropropagation, this program developed a pipeline to produce new hybrid varieties with improved resistance to P. cinnamomi. Micropropagation helps to overcome the recalcitrance that chestnut tissues present to traditional clonal propagation techniques. This work describes the pipeline of production of these hybrids and characterizes the plants from in vitro to ex vitro conditions. The pipeline allows the development of healthy plants capable of robust and continuous growth in ex vitro conditions. Nowadays these hybrids are being multiplied in a large scale production system, to be released to the market in the near future.

An In Vitro Protocol for Propagating Castanea sativa Italian Cultivars

“…For ‘Garrone Rosso’ ( Figure 5 ), both for DKW (2.31 ± 0.3) and for MS3B (2.0 ± 0.2), the multiplication rate was significant higher compared to that for the GD medium (0.5 ± 0.15). Our results are consistent with the multiplication rates (approximately 2.5 to 3.0 of new shoots/explant) observed by Fernandes et al [ 20 ] Ballester et al [ 44 ] and Miranda and Fernandez [ 45 ]. Our results suggest a higher multiplication rate in DKW, which makes it a good multiplication medium for both ‘Marrone di Castel del Rio’ and ‘Garrone’ cultivars.…”

“…Following Fernandes et al [ 20 ], WPM [ 47 ] medium supplemented with zeatin was successfully used for shoot elongation of ‘Marrone di Castel del Rio’ and ‘Garrone Rosso’. For ‘Garrone Rosso’, the number of leaves and the shoot length were 7.4 ± 0.7 mm and 29.3 ± 1.96 mm, respectively, while, for ‘Marrone di Castel del Rio’, they were 10.23 ± 1.12 mm and 35 ± 2.2 mm, respectively.…”

“…Although in vitro culture protocols have already been developed for the genus Castanea [ 1 , 4 , 5 , 17 , 18 , 19 , 20 , 21 ], large-scale propagation of C. sativa is currently not yet possible since it is a genotype-dependent technique and requires specific protocols for each species and cultivar, making it impossible to adopt a universal protocol. For this reason, since in vitro culture protocols for Italian varieties are not available, this research was focused on developing a protocol to micropropagate C. sativa cv.…”

European and American chestnuts: An overview of the main threats and control efforts

“…Later, in the 1990s, Professor Lopes Gomes started a breeding program at the University Trás-os-Montes e Alto Douro developing 53 genotypes resistant to ink disease (Table 2; Gomes Laranjo et al, 2007;Martins et al, 2009). More recently, in 2006, a breeding program was initiated (Costa et al, 2011) from which four F1 hybrids were selected for large-scale propagation due to their ability to multiply and root in vitro, field development and PC resistance levels (Table 2; Santos et al, 2015a;Fernandes et al, 2020aFernandes et al, , 2021a.…”

Effect of Sucrose on Growth and Stress Status of Castanea sativa x C. crenata Shoots Cultured in Liquid Medium

“…As chestnut is highly recalcitrant to conventional vegetative propagation, agar-based micropropagation protocols have been developed [ 19 , 20 ]. Despite recent progress [ 21 , 22 , 23 ], the commercial vegetative propagation of chestnut species is still a bottleneck for the forest industry, mainly due to problems in rooting and acclimation (reviewed in Vielba et al [ 1 ]). Actions aiming to increase root quality and acclimation efficiency should be directed to improve both shoot and root performance.…”