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Agriculture, Dairy & Animal Science
Prunus is a genus from the Rosaceae family that encompasses about 230 species that are widely distributed across the world. Three-quarters of the Prunus species are native to Asia, Europe, and North America, and the remaining other species are native to the subtropical and tropical forests of Asia, Africa, South America, and Australia. The most common recent ancestor of Amygdalus was widespread from West Asia to Eastern Asia (China) ~50 million years ago, with a subsequent diversification into almonds in West Asia and peaches in Eastern Asia.
- peach
- fruits
- rootstocks
1. Introduction
There has been remarkable progress in the development of new rootstocks for stone fruits. Interspecific hybrids between different Prunus species confer traits that P. persica lacks, such as growing in nonoptimal and low-chill areas, adaptation or tolerance to heavy soils, waterlogging, alkalinity, drought, reduced vigor for higher planting densities, and soil pathogens, among others [25], with a broad graft compatibility within Prunus [5,24].
Given the wide variability and contrasting differences between the cultivar traits, it is not easy to mention their features as a group of plant materials. However, it can be noticed that, in general, many peach rootstocks are more tolerant to nematodes, peach × almond hybrids are more tolerant to alkalinity and drought, and peach–plum hybrids are more tolerant to waterlogging (Table 1).
Table 1. A detailed comparison of the advantages and disadvantages of rootstocks for commercial peach production in the Southeastern United States.
| Rootstocks | Cultivar | Advantages | Disadvantages | Source |
|---|---|---|---|---|
| Peach (Prunus persica) |
‘Nemaguard’ |
|
|
(Handoo et al. 2004; Nyczepir et al. 1983; Zehr et al. 1976) |
|
Root-lesion nematode (Pratylenchus vulnus) | |||
|
Fungal root rots | |||
| Meloidogyne incognita | Verticillium | |||
| M. javanica | Ring nematode (M. xenoplax) | |||
| M. arenaria |
|
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| Crown gall (relatively) | Iron chlorosis | |||
| Root waterlogging | ||||
|
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| ‘Nemared’ |
|
|
(Reighard & Loreti 2008) | |
|
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| ‘Guardian’TM |
|
|
(Blaauw et al. 2020) | |
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| M. incognita | Oak root rot (Desarmillaria tabescens). | |||
| M. javanica | Root-lesion nematode (P. vulnus) | |||
| M. arenaria | ||||
|
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| Bacterial canker | ||||
| Peach Tree Short Life (PTSL) | ||||
|
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| ‘Lovell’ |
|
|
(Reighard & Loreti 2008) | |
|
|
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|
Oak root rot | |||
|
Root-lesion nematode | |||
| Ring nematodes | Phytophthora spp. | |||
| Bacterial canker |
|
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| PTSL | ||||
| ‘Halford’ |
|
|
(Reighard & Loreti 2008) | |
|
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| ‘Bailey’ |
|
|
(Reighard & Loreti, 2008) | |
|
Root-knot nematodes | |||
|
Fungal root rots | |||
|
PTSL | |||
|
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| ‘Flordaguard’ |
|
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|
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| Peach’ almond rootstocks P. persica´ P. dulcis |
‘GF-677’ |
|
|
(Loreti & Massai 2006) |
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|
Oak root rot | |||
| M. incognita | ||||
| A. tumefaciens | ||||
| Phytophthora cactorum | ||||
| Stereum purpureum | ||||
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| ‘Sirio’ |
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| ‘Castore’ |
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| ‘Polluce’ |
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| ‘Hansen 2168’ ‘Hansen 536’ |
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(Reighard & Loreti 2008) | |
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| M. incognita | ||||
| M. javanica | ||||
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| ‘Adafuel’ |
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|
(Reighard & Loreti 2008) | |
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| Powdery mildew (Sphaerotheca pannosa) | ||||
| Plum rust (Tranzschelia pruni-spinosae) | ||||
| Shot hole (Corineum beijerinckii) | ||||
| Phytophthora spp. | ||||
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| ‘Adarcias’ |
|
(Albás et al. 2004) | ||
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| Colletotrichum beijerinckii Oud. | ||||
| T. pruni-spinosae (Pers.) Diet. | ||||
| ‘Felinem’ ‘Garnem’ ‘Monegro’ |
|
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||
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| Long vegetative period | Root-lesion nematode (P. vulnus) | |||
| Red-colored leaves | Crown gall caused by Agrobacterium tumefaciens | |||
| Low presence of feathers | ||||
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| M. incognita | ||||
| M. javanica | ||||
| Peach ´ plum rootstocks P. persica ´ P. cerasifera |
‘Ishtara’ |
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| ‘Myran’ |
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| M. arenaria | ||||
| M. javanica | ||||
| M. incognita | ||||
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| ‘MP-29’ |
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(Beckman et al. 2012) | |
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| PTSL | ||||
| M. incognita | ||||
| M. floridensis | ||||
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| ‘Controller 5’ |
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| ‘Controller 9’ |
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| ‘Krymsk 86’ |
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| ‘Sharpe’ |
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| Armillaria root rot (Desarmillaria tabescens) | ||||
| PTSL | ||||
| M. floridensis |
2. Peach Rootstocks
Peaches belong to Euamygdalus species cultivars, from Subgenus Amygdalus [91], one of the three traditionally identified rootstocks groups based on their genetic origin. In addition, it is noteworthy that open-pollinated peach seedlings are still the most widely used rootstock for peaches worldwide [20]. Actually, the only recommended rootstock for commercial peach production in Florida is ‘Flordaguard’ [92].
Nevertheless, other species belonging to the Euamygdalus section are peach (P. persica) wild relatives, such as P. davidiana, P. kansuensis, P. mira, and P. ferganensis, which evolved in China. The crosses of these “wild peaches” with P. persica have produced good quality rootstocks [93].
A wide number of different P. persica cultivars are used as rootstocks for peach production worldwide, making it difficult to generalize their features. Thus, the peach rootstocks advantages and disadvantages are going to be mentioned based on the most-used (>95%) P. persica cultivars as rootstocks for peach production in the United States, including ‘Floridaguard’, according to Reighard and Loreti [20]: ‘Lovell’, ‘Halford’, ‘Nemaguard’, ‘Nemared’, ‘Bailey’, and ‘Guardian’TM.
In field-testing, these rootstocks differ in vigor, root-knot nematode resistance, and bacterial canker (i.e., PTSL) tolerance but have similar effects on many other horticultural traits. These peach seedling rootstocks are susceptible to the same soil diseases and conditions, limiting their productivity and longevity in many otherwise good production sites [20].
2.1. ‘Nemaguard’
‘Nemaguard’ rootstock exhibits uniform and vigorous seedlings. It imparts excellent scion vigor and productivity. Additionally, it has good resistance to M. Incognita, M. Javanica, and M. Arenaria [39]. However, it is sensitive to Pratylenchus vulnus, fungal root rots, Verticillium, iron chlorosis, and root waterlogging. It may reduce the winter hardiness of scion cultivars in cold climates. It produces suckers extensively. It is very sensitive to ring nematode (M. Xenoplax), which makes the tree more susceptible to bacterial canker and PTSL. It is fairly tolerant to crown gall [94,95].
2.2. ‘Nemared’
‘Nemared’ rootstock exhibits uniform and vigorous seedlings. The seedlings have few lateral branches, which facilitates budding. It produces a slightly more vigorous tree with equal or better root-knot resistance. However, it is highly susceptible to bacterial cankers [20].
2.3. ‘Guardian’TM
‘Guardian’ rootstock exhibits uniform and vigorous seedlings. It imparts excellent scion vigor and productivity. It has good resistance to M. incognita, M. javanica, and M. arenaria. It has a higher tolerance to ring nematode, bacterial canker, and PTSL. It survives better than other commercial peach rootstocks, including ‘Lovell’, on sandy, replant sites infested with ring nematodes (M. xenoplax) in the southeast [96]. Among its disadvantages, it has lower seed germination and has slightly less root-knot nematode resistance than ‘Nemaguard’ [97,98,99,100]. Additionally, it is susceptible to oak root rot and to P. vulnus (root-lesion nematode) [96].
2.4. ‘Lovell’ and ‘Halford’
‘Lovell’ and ‘Halford’ rootstocks present high seed germination and uniform seedlings. ‘Lovell’ does not produce suckers and has a better tolerance to ring nematodes, bacterial canker, and PTSL than ‘Nemaguard’. However, its scion vigor is slightly less than ‘Nemaguard’. ‘Lovell’ is susceptible to root-knot and root-lesion nematodes, as well as crown gall, P. vulnus, Phytophthora spp., and Armillaria spp. Additionally, ‘Lovell’ is susceptible to waterlogging. ‘Lovell’ rootstock is no longer used as a commercial cultivar [20].
2.5. ‘Bailey’
‘Bailey’ rootstock exhibits uniform seedlings with good vigor. It has good cold hardiness for a peach and is fairly tolerant to root-lesion nematodes. Usually, ‘Bailey’ produces a slightly smaller tree than ‘Lovell’ but is very productive. It is a popular rootstock on sandy soils in more northern climates. However, ‘Bailey’ is susceptible to root-knot nematodes, waterlogging, fungal root rots, and PTSL in the Southern United States [20].
2.6. ‘Flordaguard’
Peach seedlings generally show susceptibility to root-knot nematodes, but ‘Nemaguard’ and ‘Okinawa’ showed tolerance to a nematode attack [101]. These two materials with ‘Nemared’ have been the most used rootstocks in Florida for years. However, they are not tolerant to root-knot M. floridensis found in Florida soils. ‘Flordaguard’ rootstock was released as a solution to this challenge. ‘Flordaguard’ is a low-chill, nematode-resistant peach rootstock developed for Florida soils, where M. floridensis is found. This rootstock has improved root-knot nematode resistance and is red-leaved, which allows for the easy detection and removal of rootstock suckers [102]. Additionally, it is single-seeded and, thus, does not have to be cracked for seed separation before planting [19]. It was released by the University of Florida in 1991 and is currently the predominant rootstock in orchards throughout the state [19]. However, this rootstock is not tolerant to waterlogging, which is a common problem in Florida flatwoods [103]. However, it is susceptibility to iron deficiency chlorosis under alkaline conditions [104], with a. susceptibility to bark gummosis, produced by B. dothidea [105].
3. Peach × Almond Rootstocks
3.1. ‘GF-677’
‘GF-677’ rootstock is 10–15% more vigorous than peach seedlings, with a well-developed root system that ensures good anchorage and lower planting problems. It was adapted to infertile and droughty soils if they are permeable and well-drained. It is highly tolerant to iron chlorosis (good productivity even in soils with 10–12% limestone). It tolerates moderate salinity levels. It has become the most widespread rootstock in the peach-growing areas in Europe, mainly the Mediterranean Basin [106]. However, among its disadvantages, it produces high branching in the nursery and does not perform well in replant conditions [106]. It induces low yields, smaller fruit sizes, and poor fruit color in the first few years because of its excessive scion vigor [20]. It is not recommended for very fertile soils or high planting densities; it is sensitive to root waterlogging, and it is susceptible to A. mellea, M. incognita, A. tumefaciens, Phytophthora cactorum, and Stereum purpureum. Additionally, it is fairly susceptible to V. alboatrum [64].
3.2. ‘Sirio’
‘Sirio’ rootstock can be propagated by cuttings and, even more efficiently, with in vitro micropropagation. It produces a good root system and is adapted to fertile and permeable soils. It is resistant to iron chlorosis. It induces trees about 40% smaller than ‘GF77’, with an earlier yield. The ‘Sirio’ rootstock has a better crop efficiency than ‘GF77’, with larger fruit sizes and improved fruit color. It is suitable for high-density planting systems on fertile and chlorosis-inducing soils [107]. However, it exhibits poor root induction ability and is difficult to propagate by cuttings and layering.
3.3. ‘Castore’
‘Castore’ rootstocks can be micropropagated in vitro. It is semi-dwarfing rootstock, reducing the vegetative growth to about 30% less than ‘GF-677’. It induces a higher SSC, favorable sugar:acid ratio, and intense fruit color. ‘Castore’ is very suitable for fertile soils and high-density planting systems [64]. However, it has a poor root induction ability and is unsuitable for non-tiled heavy and waterlogged soils.
3.4. ‘Polluce’
‘Polluce’ is a semi-dwarfing rootstock that can be micropropagated in vitro. It is adapted to permeable soils with medium to high fertility, making this an alternative to ‘GF-677’ in medium- to high-fertility soils. It induces about 20% less vigor than ‘GF-677’, which allows closer tree spacing in orchards and easier tree maintenance. It produces good yields with a high yield efficiency and improved fruit quality [64]. However, similar to ‘Castore’, it has a poor root induction ability and is not suitable for wet, heavy, and inadequately drained soils.
3.5. ‘Hansen 2168’ and ‘Hansen 536’
These rootstocks are tolerant to drought and saline soils. Additionally, they can be micropropagated in vitro. Both are resistant to root-knot nematodes (M. incognita and M. javanica), and ‘Hansen 2168’ is moderately tolerant of Phytophthora spp. However, among their disadvantages, they are very sensitive to crown gall and Verticillium wilt. Additionally, they are not tolerant to waterlogging or calcareous soils such as ‘GF 677’ [20].
3.6. ‘Adafuel’
‘Adafuel’ rootstock is propagated easily by hardwood cuttings, with a better rooting percentage than ‘GF-677’. It is suitable for calcareous and loam soils, provided they are well-drained. It is resistant to powdery mildew (Sphaerotheca pannosa), plum rust (Tranzschelia pruni-spinosae), and shot hole (Corineum beijerinckii). It is more resistant to chlorosis than ‘GF-677’. It is resistant to Phytophthora spp. and does not seem as sensitive to Agrobacterium spp. such as ‘GF-677’ [106]. However, it is extremely vigorous and very susceptible to Meloidoigyne spp., limiting its commercial utility [20].
3.7. ‘Adarcias’
‘Adarcias’ rootstock propagates readily by hardwood cuttings and can be micropropagated in vitro [108]. It induces a lower vigor than ‘Adafuel’ and ‘GF-677’ but has a greater crop efficiency [109], which reduces the tree growth and management costs. It induces a higher fruit soluble solids content (SSC). It is resistant to C. beijerinckii and T. pruni-spinosae.
3.8. ‘Felinem’, ‘Garnem’, and ‘Monegro’
The nursery operations for these rootstocks are facilitated by their long vegetative period, red-colored leaves, and the low presence of feathers [73]. Additionally, they are as, or more, tolerant to ferric chlorosis than ‘GF-677’. They adapt well to poor soils that are well-drained [73]. They are very resistant to the main root-knot nematode species (M. incognita and M. javanica) [47,110]. They are propagated well by hardwood and softwood cuttings, as well as in vitro. However, among their disadvantages, they are sensitive to waterlogging. Additionally, they are susceptible to the root-lesion nematode P. vulnus [111] and to crown gall caused by A. tumefaciens.
In general, peach × almond hybrids are very promising materials, mainly for areas where iron chlorosis constitutes a serious limiting factor [20]. Peach × almond hybrids have been showing great success in coping with calcareous soils for peach production [61].
4. Peach × Plum Rootstocks
4.1. ‘Ishtara’
‘Ishtara’ is a non-suckering and semi-dwarfing rootstock that reduces the tree size. It induces a high productivity index and increased fruit size. It can be propagated readily by hardwood or semi-hardwood cuttings. It is more tolerant to A. mellea than peaches, and it is resistant to root-knot nematodes [112]. However, it is sensitive to winter waterlogging and induces weak anchorage in such conditions.
4.2. ‘Myran’
This rootstock is more resistant than peaches and peaches × almonds to A. mellea. It is tolerant to M. arenaria, M. javanica, and M. incognita. It is tolerant to alkaline soils (pH~8). It is more tolerant to root anoxia than peaches and peach × almond hybrids [112]. However, this rootstock is lightly more vigorous than peach seedlings and is susceptible to P. vulnus.
4.3. ‘MP-29’
‘MP-29’ rootstock shows red leaves, such as ‘Flordaguard’, which simplifies the identification and removal of rootstock suckers and resistance to PTSL such as ‘Guardian’TM and resistance to root-knot nematodes, including M. incognita and M. floridensis. It induces a similar vigor to that of ‘Sharpe’ rootstock but with higher yields of larger fruits, which increases the yield efficiency. It is readily propagated via softwood or hardwood cuttings and tissue cultures. It induces a significantly lower vigor than trees budded on peach seedling rootstocks ca. 70% the sizes of trees on ‘Guardian’TM. It produces fewer root suckers than ‘Guardian’TM. The yield efficiency is equal to or better than the trees on ‘Guardian’TM. It is significantly more resistant to A. tabescens root rot than ‘Sharpe’ or ‘Guardian’TM [35].
4.4. ‘Controller 5’ and ‘Controller 9’
‘Controller 5’ reduces the vigor 50–60%, and ‘Controller 9’ reduces ~90% of what ‘Nemaguard’ induces, significantly reducing the pruning costs and use of ladders [113]. However, they are less resistant to root-knot nematodes than ‘Nemaguard’.
4.5. ‘Krymsk 86’
‘Krymsk 86’ is a non-suckering rootstock that can be easily propagated by softwood and hardwood cuttings. It is tolerant to calcareous soils and induces more cold tolerance and precocity than peach rootstocks. Additionally, it is more tolerant to waterlogging than peach seedling rootstocks [114].
4.6. ‘Sharpe’
‘Sharpe’ is a plum hybrid rootstock of unknown origin, probably a hybrid of Chickasaw plums (P. angustifolia), discovered in Florida in 1974, named in honor to Dr. Ralph Sharpe. This rootstock cultivar was released by the USDA-ARS and the University of Florida. It exhibits a semi-dwarfing performance and is compatible with peach, nectarine, and plum cultivars. It is resistant to Armillaria root rot (A. tabescens (syn. Clitocybe tabescens)) and Peach Tree Short Life (PTSL). Additionally, ‘Sharpe’ is one of the three commercial rootstocks resistant to M. floridensis, together with ‘Flordaguard’ and ‘MP-29’. However, ‘Sharpe’ rootstock is not recommended for commercial production but for backyard orchards, since it induces smaller fruits [34].
This entry is adapted from the peer-reviewed paper 10.3390/horticulturae8070602
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