Rootstock Varieties Research Articles

Effect of the Substrates on the Production of Engrafted Vine Cuttings in Heated Greenhouses

This article highlights the results of a long-term research project on the production of grape stalks engrafted by the desk method. The integrated impact of rootstock varieties, modes of stratification, and different substrates on vegetating vine cuttings, raised in heated greenhouses, and the capacity of their acclimatization after planting was studied. The results of the research show that rootstock variety and modes of stratification influence the output of engrafted vegetating cuttings of vines grown in pots using various substrates. In particular, the engrafted cuttings of variety Rkatsiteli produced on two rootstocks, 5 BB and 101-14, passed stratification (a) in sawdust with local electroheating, (b) on the water with its periodic change, and (c) in the layer of perlite. After preplanting preparations they were planted in pots with six different substrates: (1) soil (control); (2) perlite; (3) sawdust; (4) rice husk + soil + sand (1:1:1); (5) peat + soil + sand (1:1:1); and (6) mold + soil + sand (1:1:1). The cuttings were grown with a covered root system in a heated greenhouse for 35–40 days. Forty-day-old vegetating cuttings, after hardening, were planted into the open ground. Specialties were established during the root and shoot formation on vegetating nursery plant grafts during the rooting period. Optimal substrates for growing engrafted cuttings with a covered root system in heated greenhouses for each rootstock and stratification mode were determined.

Phosphorus Uptake by Young Citrus Trees in Low-P Soil Depends on Rootstock Varieties and Nutrient Management

Because low-phosphorus (P) availability limits citrus growth, rootstocks with a relatively high capacity for P uptake are desirable. An experiment was conducted with trees on Cleopatra mandarin (CM) and Rangpur lime (RL). Treatments consisted of P rates (20, 40, and 80 mg kg−1 of soil) applied in soil layers of 0–0.30 m and/or 0.31–0.60 m, besides an unfertilized control. The P fertilization increased root and shoot growth, and P nutrition was improved as indicated by greater leaf P concentration, P uptake, and P root uptake efficiency (PUE). The P applied in both soil layers improved shoot growth, P uptake, and PUE. Trees on RL took up 23–126% more P and had root systems with greater growth and PUE compared to those on CM. Thus, P uptake by citrus trees in low-P soils can be improved by augmenting the depth of fertilizer application and the use of more adapted rootstocks.

Development of a Nested Quantitative Real-Time PCR for DetectingPhytophthora cinnamomiinPersea americanaRootstocks

Phytophthora cinnamomi causes Phytophthora root rot (PRR) in avocado (Persea americana), an important disease that causes severe economic losses to the avocado industry globally. To date, no PRR-resistant avocado rootstock variety has been discovered, although certain rootstock varieties have been shown to be more tolerant than others. In this study, we developed an accurate, low cost assay for in planta quantification of P. cinnamomi to evaluate disease tolerance. A nested real-time polymerase chain reaction assay was developed to sensitively detect pathogen DNA in plant tissues. Root samples from a highly tolerant (Dusa) and less tolerant (R0.12) rootstock were collected at 0, 3, 7, 14, and 21 days after inoculation with P. cinnamomi and used for pathogen quantification. Nested primers developed in this study were specific and sensitive and could detect P. cinnamomi in root tissues. The amount of P. cinnamomi quantified in roots was significantly higher in the less-tolerant R0.12 plants when compared with the highly tolerant Dusa plants at all time points. This study has confirmed the known status of disease tolerance of Dusa and R0.12 avocado rootstocks in a quantitative manner and provides a reliable molecular tool to assist with industry breeding programs for the selection of PRR-resistant avocado rootstock varieties.

Susceptiblity of common rootstock and scion varieties of grapevines to Botryosphaeriaceae species

This study investigated the susceptibility of the most common rootstock and scion varieties used in New Zealand grapevine nurseries and vineyards to Botryosphaeriaceae species. A total of six rootstocks and six scion varieties were inoculated with mycelium of three isolates each of the most common Botryosphaeriaceae species (Neofusicoccum luteum, N. parvum and N. australe) recovered from New Zealand grapevine nurseries. Overall results showed that all isolates produced necrotic lesions on all varieties but susceptibility varied significantly (P < 0.001) with 5C and SO4 being the most susceptible of the rootstock varieties, and Merlot and Pinot noir being the most susceptible of the scions. Pathogenicity also varied significantly (P < 0.001) between species with N. parvum being the most virulent among three species tested. This study has further shown that different isolates of the three species have different levels of virulence providing evidence that these pathogens are genetically diverse. These results have significant implications for the New Zealand grapevine industry as the use of resistant varieties is not a possible option at present since none of the common varieties are resistant to these pathogens.

Identification of citrus varieties using laser-induced fluorescence spectroscopy (LIFS)

The production of sweet orange faces a problem with regard to visually identifying citrus seedling varieties. Despite using analytical techniques such as molecular markers, this kind of classification is not possible due to very subtle genetic variations. This is an important fact given that the cultivation of a variety that differs from the one planned can cause numerous serious problems, such as the treatments applied to the orchards as well as the quality and characteristics of the fruits after harvest. Within this context, we assess the laser-induced fluorescent emission technique (LIFS) as a tool to identify citrus varieties. The results showed that LIFS combined with statistical methods is able to discriminate the different citrus varieties chosen. The rate of success for this classification depends on the combination of canopy and rootstock varieties, and our best result was of around 100%. These results can be used in the development of a new method that is economically viable for seedling certification.

The impact of various grape stock cultivars on the As, Cu, Co and Zn content of the grape berry (must, seed)

Scientific research from the last decades showed that the inappropriate industrial and agricultural production caused an abnormal increase of the potentially toxic elements in the soil. Unfortunately the acidification of the soil is an increasing problem in Hungary. According to Várallyay et al. (2008) 13% of the Hungarian soils are highly acid. Accumulation of toxic elements differs in the genetically diverse plant species. The root of the plant constitutes a filter so that the rootstock is also kind of a filter system, which may prevent that the scion part (such as berry) accumulate high levels of various potentially toxic elements from the soil. The aim of research was to determine how different grape rootstocks influence the As, Co, Cu and Zn content of the musts and seeds. Thus, specifying which of the grape rootstocks takes up the lowest level of these 4 elements (As, Co, Cu and Zn), and accumulates in berries, so could reduce the potentially toxic element load of the grape berries. The grape rootstock collection of the University of Debrecen was set up in 2003 in 3x1 m spacing on immune sandy soil. Grafting of ‘Cserszegi fűszeres’ was started in 2010. We could evaluate yields harvested from 12 rootstock varieties of the experiment in October 2011. We obtained valuable differences in the arsenic, copper, cobalt and zinc concentrations of musts and seeds of ‘Cserszegi fűszeres’ grafted into different rootstocks. The results obtained from the 2011 harvest support the statement that the choice of rootstock might be an important factor to increase food safety. The differences in concentration of the four elements observed in case of the rootstock may have been caused on one hand by the rootstock effect, and on the other hand, the vintage effect has a very significant impact on the vines element uptake. Several years of experimental results will be needed to answer these questions.

THE EFFECT OF ROOTSTOCK AND SPACING ON THE GROWTH AND YIELD OF 'KÁNTORJÁNOSI 3' SOUR CHERRY VARIETY IN INTENSIVE ORCHARD

In our trial eight different varieties of sweet and sour cherry rootstocks were examined in three different spacing, what was carried out in Experimental and Research Farm of Corvinus University of Budapest. The aim was to find rootstocks with drought tolerance in different vigorous for the ‘Kantorjanosi 3’, which a wide-spread sour cherry variety at Hungary. The rootstocks were tested (P. mahaleb: ‘CEMA’ and ‘Korponay’ seedlings, ‘SL 64’, ‘Bogdany’ and ‘Magyar’; P. fruticosa: ‘Prob’; Prunus hybrids: ‘Colt’ and ‘Pi-Ku 2’ vegetative propagated) in variant spacing (4x2,5; 4x2; 4x1,5 m). Trees were formed to slender spindle, what is suitable for modern fruit growing. Our results show that this type of crown can be applied at medium and strong vigorous rootstocks in different spacing. In extensive condition, large spacing (4x2-2.5 m) with strong vigorous rootstocks (Prunus mahaleb varieties) are recommended. ‘Magyar’ is also suitable under these conditions, and the spacing can be reduced to 4x1.75 m. The vigour of ‘Prob’ is not enough to the applied spacing. Under these conditions, it is difficult to keep the slender spindle form. Trees on these rootstocks with Zahn-spindle form in higher density could be efficient with modern irrigation, fertilization and training system. The ‘Prob’ rootstock resulted one of the best fruit size. Based on our results we do not recommend for ‘Kantorjanosi 3’ ‘Colt’ and ‘Pi-Ku 2’. The branches died and leaves turned yellow on ‘Pi-Ku 2’. ‘CEMA’ and ‘Korponay’ with strong vigorous gave better yield. Medium vigorous ‘Magyar’ was also suitable in higher tree density. Compared the data we can see that using larger spacing increases the yield significantly. On the other hand the specific yield index does not show significantly difference at the different spacing. Summarizing our results we can state that increasing the density in the orchard, the yield does not decrease significantly. We can reduce spacing as long as the vigorous of rootstocks-scion combination can allow it.

Monitoring the viability of citrus rootstocks seeds stored under refrigeration

The citrus nursery tree is produced through the bud grafting process, in which rootstock is usually grown from seed germination. The objective of this research was to evaluate, in two dissimilar environmental conditions, the viability and polyembryony expression of five citrus rootstocks seeds stored in different periods under refrigeration. The rootstock varieties evaluated were: Rangpur lime (Citrus limonia Osb. cv. Limeira), Trifoliate orange (Poncirus trifoliata Raf. cv. Limeira), Citrumelo (P. trifoliata x C. paradisi Macf. cv. Swingle), Sunki mandarin (C. sunki Hort. ex Tanaka) and Volkamer lemon (C. volkameriana Ten. &amp; Pasq. cv. Catania 2). The experimental design was the randomized blocks in a 11 x 5 x 2 factorial scheme, evaluating from time zero to the tenth month of storage, the five varieties of rootstock in two environments: germination and growth B.O.D type chamber (Biological Oxygen Demand - Eletrolab Brand Model FC 122) at 25 °C; and greenhouse seedbed with partial temperature control (22 °C to 36 °C) and humidity control (75-85%). The plot had 24 seeds in four replicates, using trays with substrate in greenhouse and Petri dishes with filter paper in B.O.D. chamber. The seed germination rate and polyembryony expression were evaluated monthly. It was concluded that Trifoliate and Citrumelo Swingle seeds can be stored for up to seven months, while Volkamer lemon, Rangpur lime and Sunki seeds can be stored for up to ten months. The polyembryony expression rate was slightly higher when measured in greenhouse than in B.O.D. chamber and remained stable in both environments until the seventh month, from which dropped sharply. Citrumelo Swingle seeds expressed the highest polyembryony rate (18.8%), followed by Rangpur lime and Volkamer lemon (average value of 13.7%), Sunki (9.4%) and Trifoliate (3.2%). Despite some differences among varieties, the viability of rootstock stored seeds can be monitored either in the greenhouse or in B.O.D. germination chamber, the latter being the faster and more suitable method.

Susceptibility of four grapevine rootstocks to Cylindrocladiella parva

The susceptibility of four common grapevine rootstocks (10114 Schwarzmann 5C and Riparia Gloire) to Cylindrocladiella parva (black foot disease) infection was assessed in a pot experiment The roots of 4monthold callused rooted cuttings were wounded in situ and inoculated with 50 ml C parva conidial suspension (106/ml) or sterile water (controls) After 6 months of growth shoot dry weight was significantly higher for control plants (242 g) than for those inoculated with C parva (165 g) but did not differ between rootstock varieties Root dry weight was not significantly affected by C parva inoculation but root dry weight of 10114 was significantly higher than other rootstocks Incidence and severity of trunk infection were significantly affected by rootstock variety being lowest in rootstock 10114 plants than other rootstocks None of the rootstocks tested was resistant to this pathogen

两种苹果砧木根系水力结构及其PV曲线水分参数对干旱胁迫的响应

研究干旱胁迫对平邑甜茶(<em>Malus hupehensis</em>)和楸子(<em>Malus prunifolia</em>)根系水力结构及其PV曲线水分参数的影响。设定正常与干旱2种水分处理,对2种苹果砧木进行氯化汞-巯基乙醇处理和压力室-容积(PV)曲线测定试验,并利用高压流速仪(HPFM),测定平邑甜茶和楸子根系水力结构。结果表明:随着水分胁迫的加重,平邑甜茶和楸子的根系导水率、根系叶比导水率、根系茎比导水率出现减少趋势。在适宜水分和重度干旱条件下,平邑甜茶根系叶比导水率分别为楸子根系叶比导水率的95%和92%,平邑甜茶根系茎比导水率分别为楸子根系茎比导水率的52%和62%,楸子与平邑甜茶相比在根系茎比导水率和根系叶比导水率上出现增加趋势。干旱胁迫可能会导致水通道蛋白的活性受到抑制,致使其根系导水率出现降低,继而导致了地上部分气体交换受到影响。严重干旱时,楸子与平邑甜茶相比可能具有更大的水孔蛋白表达量来抵御干旱胁迫。在2种水分条件下,楸子的初始质壁分离时的渗透势(<em>ψs</em>^tlp)、饱和含水时的渗透势(<em>ψs</em>^sat)、初始质壁分离时的相对水含量(RWC^tlp)、初始质壁分离时的相对渗透水含量(ROWC^tlp)、组织细胞总体弹性模量(ε')值与平邑甜茶相比较均处于较低水平,束缚水含量(<em>Va</em>)值处在较高水平。对PV曲线水分参数进行隶属函数综合评价得出的<em>Δ</em>值为楸子大于平邑甜茶,平邑甜茶和楸子之间<em>b</em>值差异不明显。在适宜水分和重度干旱条件下楸子所体现出的输水策略优于平邑甜茶。PV曲线水分参数同苹果砧木根系的水力结构一样能够随着植物所处的环境做出相应的调整。对于PV曲线水分参数研究发现,楸子在膨压保持方面与平邑甜茶相比,其抗旱性优于平邑甜茶。;Water deficit is a growing problem affecting the production of high quality apple fruit in many different parts of the world, including the northwestern region of the Loess Plateau of China. The use of genetically drought-resistant rootstocks is a promising water-saving practice in these apple-producing regions. To understand the mechanisms of water absorption and to better evaluate drought-resistant apple rootstocks, research on the relationship between hydraulic conductance, aquaporins, and osmosis adjustment in apple rootstocks during water stress is critical. In this study, we measured the effects of water deficit on hydraulic architecture and pressure-volume curve parameters of <em>Malus hupehensis</em> ‘Pingyitiancha' and <em>M. prunifolia</em> ‘Qiuzi'. Experiments were carried out on both rootstocks using two different treatment regimes; a suitable soil moisture treatment with soil water at 70%-75% of field capacity, and a drought stress treatment with soil water at 40%-45% of field capacity. Root hydraulic conductance was determined from mercuric chloride-mercaptoethanol immersion treatments, which trigger reversible inhibition of aquaporins, using a high-pressure flow meter (HPFM). Gas exchange was measured with a CIRAS-2 portable photosynthesis system. A pressure-volume curve was constructed from parameters obtained using a Model-1000 PMS pressure chamber. Hydraulic conductance, leaf area specific conductance, and sapwood area specific conductance in roots of <em>M. hupehensis</em> and <em>M. prunifolia</em> decreased when subjected to drought stress. Under conditions of suitable soil moisture, leaf area specific conductance and root sapwood area specific conductance for <em>M. hupehensis </em>were 95% and 52%, respectively, of those obtained for <em>M. prunifolia</em>; under severe drought conditions, these values were 92% and 62% of <em>M. prunifolia </em>measurements. <em>Malus prunifolia</em> had higher leaf area specific conductance and root sapwood area specific conductance than <em>M. hupehensis</em>. Drought stress can reduce aquaporin activity, thus decreasing root hydraulic conductance and subsequently affecting net photosynthetic rate, transpiration, stomatal conductance, and intercellular CO₂ concentration of aerial parts. Therefore, to resist water stress under severe drought, <em>M. prunifolia</em> may be able to express higher levels of aquaporins than <em>M. hupehensis</em>. Under both treatment conditions, osmotic potential at turgor loss point (<em>ψs</em>^tlp), osmotic potential at saturated point (<em>ψs</em>^sat), relative water content at turgor loss point (RWC^tlp), relative osmotic water content at turgor loss point (ROWC^tlp) and maximum bulk elastic modulus (ε') were higher in <em>M. hupehensis</em> than in <em>M. prunifolia</em>, whereas bound water content (<em>Va</em>) was higher in <em>M. prunifolia</em>. Comprehensive evaluation of pressure-volume curve parameters using subordinate function analysis revealed that the average value of the subordinate function (<em>Δ</em>) of <em>M. prunifolia</em> was larger than that of <em>M. hupehensis</em>; however, the slope (<em>b</em>) of the linear regression line between turgor pressure and leaf water content did not significantly differ between <em>M. prunifolia </em>and <em>M. hupehensis</em>. These results show that under both conditions, <em>M. prunifolia</em> employed a better water-use strategy than <em>M. hupehensis. </em>Both rootstock varieties were able to respond to changing environmental conditions by adjusting pressure-volume curve parameters and hydraulic architecture. Investigation of pressure-volume curve parameters revealed that <em>M. prunifolia </em>had a greater ability to maintain turgor and was more drought resistant than <em>M. hupehensis</em>.

Tolerance of trifoliate citrus rootstock hybrids to Candidatus Liberibacter asiaticus

Candidatus Liberibacter asiaticus (Las) is the suspected causal agent of Huanglongbing (HLB) in Florida and other citrus producing countries around the world. Although little resistance to HLB is found within commercial citrus varieties, tolerance has been reported for some varieties that are commonly used as rootstocks. This study assesses the response of eight different rootstock varieties, which include the Citrus×Poncirus trifoliata hybrids Carrizo citrange, US-802, US-812, US-897, and US-942, Benecke trifoliate orange, Volkamer lemon, and Cleopatra mandarin, to Las under controlled conditions in the greenhouse. The percentage of plants detected positive for Las did not exceed 7% in the genotypes Benecke, Carrizo, US-802, US-942, and Volkamer during the first 6 months after graft-inoculation (mai). Pruning resulted in much increased numbers of plants with detectable Las levels and induced disease symptoms in previously asymptomatic plants. At 12 mai, percentages of Las-positive plants were 91–96% for US-802, US-812, Cleopatra, and Volkamer, and 70–78% for US-897 and US-942. Lowest percentages (44–52%) were observed for Benecke and Carrizo. The number of Las genomes per g of leaf tissue in Las-positive plants was considerably lower in Benecke and US-897 seedlings with 4.5×105 and 1.6×106 compared with Cleopatra (1.0×107), while numbers for the other genotypes ranged from 3.1–4.9×106. At 12 mai, foliar disease symptoms, though variable in extent, were prominent in most genotypes, except US-897. Shoot masses were significantly reduced in Cleopatra, Benecke, US-802, and Volkamer seedlings in response to Las at this time. Continued observation until 18 mai found no significant growth reductions in Benecke seedlings. Our results suggest classifying Carrizo, US-897, and US-942 as tolerant, US-802, US-812, and Volkamer lemon as moderately tolerant, and Cleopatra mandarin as susceptible to Las. Despite irregular growth, low rates of infection and low Las numbers indicate some resistance of Benecke to Las. Additional greenhouse experiments and field observations confirmed findings for US-802, US-897, US-942, and Cleopatra, although results for US-802 were more variable.

Investigation of tissue structure and xylem anatomy of eight rootstocks of sweet cherry (Prunus avium L.)

Reduction of crop yield from high water stress is a serious agricultural problem worldwide, which is expected to intensify under future global change scenarios. Efforts are underway worldwide to improve crops resistance to drought. One possible way is the careful choice of rootstock-scion combination. It is well known that water stress symptoms of grafted cherry trees to a large extent depend on the rootstock variety. Scions grafted on dwarf rootstocks show more serious stress symptoms, so it is reasonable to hypothesize that these symptoms and the tissue structure of the rootstock stem are connected. This paper examines this connection for 1-year-old seedlings of eight cherry rootstocks with different degree of vigor. Tissue structure was observed via scanning electron microscope images. Investigations were focused on number, size, and distribution of vessels, because they are principally responsible for water transport. Stem porosity (i.e., the total vessel area relative to the stem area, in cross-sectional view) of the dwarfing rootstocks was found to be significantly smaller than that of the others, supporting the notion that stem anatomical characteristics might contribute to water stress sensitivity.

Screening of rootstock hybrids with Vitis cinerea Arnold for phylloxera resistance

AbstractThe resistance to phylloxera is one of the most important properties of grapevine rootstock. The breeding and selection of rootstock varieties represents a biological method of fight against phylloxera. In this study altogether 59 rootstock hybrids originating from nine different populations were evaluated. Pedigrees of all populations involved Vitis cinerea Arnold introduced through the hybrid Bruci/(Vitis berlandieri Planch. × Vitis rupestris Scheele) × Vitis cinerea Arnold/ and the variety Börner. Pot experiments were performed in a glasshouse while those with excised root pieces in root bioassay took place in a laboratory. This combination showed to be a very good selection tool for rootstock breeding. In seven rootstock hybrids, it was found that the resistance to phylloxera gallicoles and radicicoles was very high. The highest number of resistant hybrids was found in Binova × Börner. The variety Börner showed to be the best gene source of phylloxera resistance and even in case of a simple crossing produced sufficient number of resistant progeny.

Influence of rootstock variety on Huanglongbing disease development in field-grown sweet orange (Citrus sinensis [L.] Osbeck) trees

Huanglongbing (HLB), a bacterial disease of citrus, is causing substantial economic losses to the citrus industry worldwide. Sweet oranges are highly susceptible to the disease, and account for nearly 90% of all varieties grown in Florida. Rootstock is an important component of commercial citrus production, and tolerance to HLB has been reported for some rootstock varieties. Our objective was to investigate if rootstock selection has an effect on HLB disease development under natural conditions in the field. Four field trials with sweet orange scion on 15 different rootstocks were evaluated for incidence of Candidatus Liberibacter asiaticus (Las), the suspected causal agent of HLB, as well as incidence of foliar disease symptoms, canopy damage, and stem growth during the first years after Las began to spread into the trials. Trials ranged from two to nine years in age and included hybrids of trifoliate orange along with other rootstocks standard for citrus production in Florida. Fruit yield and soluble solids content were analyzed for the oldest trial. Our study showed that rootstock did not affect disease incidence and that trees on all rootstocks were considerably damaged by HLB. However, tolerance to HLB was higher in trees grafted on some rootstock selections. In the youngest trial, stem diameters on Volkamer lemon increased 53% while trees on US-852, Benton citrange and Swingle citrumelo grew the least at 21–26% from 2008 to 2010. Depending on trial and time of observation, foliar HLB symptoms on US-897 were less than on many other rootstocks, with ranks of 3.3–4.0 compared with 4.5–4.9 observed for US-812, US-852, Carrizo citrange and Kinkoji. Canopy damage ranks were 1.4–2.6 for trees on US-802 compared with 3.9–4.1 for trees on US-812, U-852, Sour orange, and Swingle in the oldest trial. In the youngest trials, trees on Volkamer showed least canopy damage while trees on US-852 and Benton were more affected. Highest fruit yields of 30–64kg/tree were obtained from trees on US-802 and Carrizo. In 2010, highest juice soluble solids content of 2.8–2.9kg was observed for trees on US-897 and US-812.

The fatty acid and tocopherol constituents of the seed oil extracted from 21 grape varieties (Vitis spp.)

Fatty acids and tocopherols in appropriate quantities are invaluable attributes that are desirable in seeds of agricultural products. Studies have generally focused on the evaluation of the oil and tocopherol components of oil crops. Recently, investigations revealed that the grape seed has robust potential in the production of healthy fatty acids as well as tocopherols. This study was thus conducted to determine the oil and tocopherol components of grape seeds, obtained from various grape cultivars of different species, including two rootstock varieties. The grape seed oil concentration of the studied varieties ranged from 7.3 to 22.4%. The determined fatty acid profiles of the genotypes conformed to the pattern described in the literature for grapes. Linoleic acid is the major component comprising 53.6-69.6% of the total, followed by oleic (16.2-31.2%), palmitic (6.9-12.9%) and stearic (1.44-4.69%). The oils of all the seeds analysed showed a preponderance of α-tocopherol (ranging from 260.5 to 153.1 mg kg⁻¹ oil extract). β-Tocopherol, γ-tocopherol and δ-tocopherol were also detected with the general means of 0.98, 22.2 and 0.92 mg kg⁻¹, respectively. Linoleic acid showed a significantly negative correlation with all the fatty acids analysed. The strongest negative correlation existed between linoleic and oleic acids (r = -0.834, P < 0.01). Present investigations indicated that oil content, fatty acid composition and tocopherol constituents of grape seed show great variation among the genotypes. Markedly higher proportions of linoleic acid with considerable amounts of tocopherols found in the oil samples suggest that grape seed is a good source for culinary, pharmaceutical and cosmetic uses.

Growth of Fig Varieties Resistant to Ceratocystis Canker following Infection with Ceratocystis fimbriata

Ceratocystis canker is caused by Ceratocystis fimbriata and is a serious soil disease affecting fig cultures. ‘Masui Dauphine’ is a major fig variety in Japan and is susceptible to this disease. In the present study, the effect of C. fimbriata infection was tested on the growth of 4 fig varieties, ‘Celeste’, ‘Boldido Negra’, ‘Ischia Black’, and ‘Negronne’. Specifically, the potential of these varieties as a disease-resistant rootstock for ‘Masui Dauphine’ was assessed. Fig cuttings of ‘Celeste’ were grown in 350 mL root boxes with sterilized coarse sand. Inoculation with C. fimbriata immediately inhibited root elongation, reduced the root respiration rate from 2 months after inoculation, and caused lesions in the rootlets. The trees of the 4 varieties tested were grown in 3.5-L pots for 5 months. C. fimbriata inoculation caused slight lesions on the underground part of all 4 varieties. Inoculation did not kill any trees and did not reduce root respiration, except with an unreasonable amount of inoculum. No significant reduction in the weights of leaves, shoots or roots was observed except for ‘Celeste’. ‘Masui Dauphine’ trees on the rootstocks of the 4 varieties tested were grown in 22-L containers for 2 years. C. fimbriata inoculation tended to inhibit scion and root growth, and killed a few trees from the 2nd year, except ‘Negronne’. ‘Masui Dauphine’ trees grafted on the rootstocks of the 4 varieties tested, in addition to 2 susceptible varieties, and own-rooted trees, were grown in the field with ceratocystis canker infection. Trees of the 4 varieties tested showed lower mortality and most survived for 5 years. No year-by-year reduction in scion growth was observed for any rootstock variety. Our results demonstrate that the varieties tested are not truly resistant, but are horizontally resistant to ceratocystis canker. We expect these rootstocks to maintain the scion ‘Masui Dauphine’ despite some continuing damage by disease. Of the varieties tested, ‘Negronne’ is the most resistant.

풋고추 접목시스템에서 Tobamovirus 감염에 의한 접수 고사

풋고추 접목시스템에서 접수 부위의 고사 원인을 구명하기 위하여 본 연구를 시도하였다. 고추 접목묘의 대목부위에서는 Tobamovirus 입자가 검출되었지만 괴사 증상이 나타난 접수 부위에서는 이 바이러스 입자를 검경할 수 없었다. 대목 부위에서 분리한 바이러스는 염기서열분석 및 기주식물의 반응으로 고추약한모틀바이러스(Pepper mild mottle virus, PMMoV)로 동정되었고, 고추 Tobamovirus pathotype P1.2(PMMoV-2)이었다. PMMoV-2는 고추 접목묘에서 대목으로 이용되고 있는 6 시판 대목 품종에 전신감염되었고, 고추 품종 롱그린맛과 대찬고추에서는 단지 접종엽에만 국부병반인 저항성 반응, 마니따에서는 전신감염을 나타냈다. 고추 대목에 롱그린맛 또는 대찬고추를 접목한 다음, PMMoV-2를 대목의 자엽에 접종하면 7일 후부터 접수의 잎에 엽맥괴사 및 시듦 증상이 나타나면서 결국 접수만 고사되었다. 이 접목시스템에서 바이러스 입자는 접수에서는 검경되지 않았으나 대목에서는 검경되었다. 그러나 PMMoV-2에 감수성 품종인 마니따를 접수로 사용한 접목시스템에서는 접수의 잎에 약한 모틀 증상이 발현되었으나 고사는 되지 않았다. Tobamovirus pathotype P1.2.3인 분리주 PMMoV-3는 이들 고추 접목 시스템에서 사용된 모든 대목과 접수에 전신감염이 되었고, 접수에 고사를 일으키지 않았다. 따라서 풋고추 접목묘에서 접수의 고사 원인은 tobamovirus pathotype P1.2에 감수성 고추 대목과 저항성 고추 접수로 조합된 접목 시스템에서 이 바이러스가 대목에 감염되었을 경우이었다. This experiment was attempted to investigate a cause of the scion death in green pepper grafting system. A tobamovirus particle examined in the rootstock of the sample but not in the scion showing necrosis. The virus isolated from the rootstock was identified as Pepper mild mottle virus (PMMoV), pepper tobamovirus pathotype P1.2. (PMMoV-2), by nucleotide sequence analysis and host plant reaction. The virus isolate infected systematically in 6 commercial rootstock varieties using for green pepper grafting seedling production. Green pepper varieties 'Long green mart' and 'Daechan' represented resistance to the virus showing local lesions only on the inoculated leaves and 'Manitda' was systematically infected. In the experiment with grafting 'Long green mart' or 'Daechan' onto the those rootstocks, the upper leaves of the scions first showed vein necrosis and wilt symptoms 7 days after inoculation with PMMoV-2 on the cotyledon of the rootstock, following to the scion stem necrosis and then only the scion death. The virus was detected in the rootstock but not in the scion. However, 'Manitda' of susceptible variety in the grafting system showed mottle symptom on the leaves of the scion but not necrosis on the plant. PMMoV-3 isolate, pepper tobamovirus pathotype P1.2.3, did not cause the scion death in the grafting system. All of the varieties were susceptible to PMMoV-3. These results suggest that the scion death is caused by infecting with pepper tobamovirus pathotype P1.2. in the green pepper grafting system combined with the susceptible rootstock and the resistance scion to the virus pathotype.

Lack of Evidence for Seed Transmission of 'Candidatus Liberibacter africanus' Associated with Greening (Huanglongbing) in Citrus in South Africa.

'Candidatus Liberibacter africanus' is associated with citrus greening (huanglongbing [HLB]) in South Africa. Various unpublished reports have suggested that the related bacterium 'Ca. L. asiaticus' associated with HLB in citrus might be seed transmissible based on real-time PCR results. Seed transmission poses a risk of long distance disease spread, especially with the dissemination of rootstock seed. Therefore, it was essential to determine whether 'Ca. L. africanus' is seed transmitted in citrus. Fruit from 26 'Ca. L. africanus'-infected branches of six citrus cultivars showing greening symptoms were collected and the seed was harvested. Cultivars included were Minneola tangelo (Citrus reticulata × C. paradisi); sweet oranges (C. sinensis) Premier midseason, Clanor midseason, and Olinda Valencia; Eureka lemon (C. limon) and Troyer citrange (Poncirus trifoliata × C. sinensis) rootstock variety. Branches bearing each fruit were collected and confirmed to contain 'Ca. L. africanus' by real-time PCR testing using Taqman probe HLBp and HLBaf and HLBr primers as described by Li et al. (3). The seed of each sample was sorted into five categories ranging from healthy looking to totally aborted based on their appearance before planting. Germination was done in seed trays under vector-free conditions at 24 to 28°C. Thereafter the seedlings were planted in small, plastic bags and monitored for greening-like symptoms or other abnormalities for up to 2 years. A slow-release, balanced fertilizer was applied and supplemented with micro-nutrient sprays for plant maintenance. Plants showing abnormal symptoms were potted into larger pots and closely monitored. These samples and a number of other seedlings showing growth abnormalities were tested for 'Ca. L. africanus' by real-time PCR as described above. In total, 1,570 seedlings were obtained. Some abnormal symptoms such as small chlorotic leaves, interveinal chlorosis, yellow veins, and stunting were seen in some seedlings. Most symptoms resembled deficiencies, and no blotchy mottle typical of 'Ca. L. africanus' infection was noted on any of the seedlings. Abnormal seedlings arose from normal and abortive seed. One hundred and eighteen of these seedlings (8 Minneola tangelo; 24 Premier midseason, 42 Clanor midseason, 33 Olinda Valencia, and 11 Troyer citrange seedlings) were individually tested using real-time PCR for 'Ca. L. africanus' detection. These seedlings had germinated from essentially healthy-looking seed (category 1) to seeds with severe abnormalities (category 5) and 33, 24, 23, 30, and 8 seedlings, respectively, were tested from each of the five seed categories. No samples tested positive with real-time PCR based on a positive/negative threshold Cq value of 35. Buds of some seedlings that yielded the lowest Cq values above 35 were grafted onto healthy 'Madam vinous' sweet orange (C. sinensis) seedlings and monitored for symptom development for 3 months. No symptoms developed and all these indicators also tested negative for 'Ca. L. africanus', indicating the absence of a transmissible agent. Just as other researchers (1,2) have recently indicated a lack of evidence for seed transmission of 'Ca. L. asiaticus', no seed transmission of 'Ca. L. africanus' could be demonstrated in this experiment either.

Colonization of Citrus and Citrus-related Germplasm by Diaphorina citri (Hemiptera: Psyllidae)

Huanglongbing (HLB) is a serious and devastating disease of citrus caused by Candidatus Liberibacter spp. and vectored by the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae). The disease has the potential to greatly limit the production of citrus in Florida and other citrus-growing regions worldwide. Current control of D. citri and HLB is inadequate, but the identification and incorporation of D. citri resistance traits from uncultivated Citrus spp. and Citrus relatives is seen as a potential disease management strategy. In this study, seedlings of 87 Rutaceae seed-source genotypes, primarily in the orange subfamily Aurantioideae, were assessed in the field for their propensity in a free-choice situation for infestations of natural south Florida populations of D. citri. The majority of test populations surveyed hosted all three life stages of D. citri; however, there were significant differences among the test populations in the mean ranks for D. citri eggs (F = 3.13, df = 86, P &lt; 0.0001), nymphs (F = 9.01, df = 86, P &lt; 0.0001), and adults (F = 4.21, df = 86, P &lt; 0.0001). The only sampled test population that was completely avoided by all life stages of D. citri was seedlings of Casimiroa edulis Llave et Lex, commonly known as white sapote, which was one of the few plants included in the study belonging to the Rutaceae subfamily Toddalioideae. Although not completely avoided, very low levels of D. citri were found on two surveyed test populations of Poncirus trifoliata (L.) Raf, seedlings of ‘Simmon's trifoliate’ and ‘Little-Leaf’. Poncirus trifoliata, the trifoliate orange, readily forms hybrids with Citrus spp., is commonly incorporated into rootstock varieties, and has been used in breeding-advanced scion material. The identification of partial resistance in P. trifoliata to D. citri could prove useful in future citrus breeding efforts aimed at reducing the incidence and spread of HLB. Determining if there is true resistance to D. citri in this and other germplasm sources with a low propensity for infestations in free-choice situations will require no-choice experiments.

Studies Regarding the Quality of the Viticultural Breeding Material in the Vine Center Blaj

Obtaining efficient yields in the wine center Blaj, as well as quality vine grafts is conditioned by a complex of technological and climatic factors. The quality of the initial material (graft and rootstock) is determined by the agro technical methods that were used. But the climatic factors from the active vegetation period and the resting period also have an important role (Ţâra et al., 1992, 1994). Knowing the maturation degree of the wood contained in the graft and rootstock cords (the content in carbohydrates: soluble sugars and starch) can be considered an important indicator that shows the deployment of the physiological processes taking place during the vegetation period (Iliescu et al., 2010). The study conducted at SCDVV Blaj followed the maturation degree of the graft and rootstock strings, during the period 2008 – 2010 in correlation with the annual climatic factors and the vine yields obtained. During the study period the carbohydrates contained in the graft and rootstock varieties from the Tarnave vineyards was dosed and it was correlated with the suitability of the meteorological factors.