Rootstock influence on the incidence of rind breakdown in ‘Navelate’ sweet orange

Summary

The influence of three rootstocks, Carrizo citrange (Citrus sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf.), Cleopatra mandarin (Citrus reshni Hort. ex Tanaka) and sour orange (Citrus aurantium L.) on the incidence and severity of rind breakdown in ‘Navelate’ sweet oranges was studied over seven years in four orchards. The proportion of affected fruit was greater in trees on Carrizo citrange (60% on an average) followed by Cleopatra mandarin (38%) and then on sour orange (9%). There were also significant differences in the severity of the disorder among rootstocks; more than 35% and 20% of fruit from trees on Carrizo citrange and Cleopatra mandarin, respectively, were rejected for commercialization, whereas only 4% of fruit on sour orange was rejected. Cryo-scanning electron microscopy (SEM) of fruit peduncles showed that average diameter of xylem vessel elements of peduncles of fruits on Carrizo citrange rootstock were 6% and 17% larger than those on Cleopatra mandarin and sour orange, respectively. Defoliation of fruit-bearing branches reduced water loss from fruit, maintained fruit peel water potential at a higher value than that of fruit on undefoliated branches and reduced the proportion and severity of affected fruit. It is concluded that fruit-tree water relationships are related to rind breakdown in ‘Navelate’ oranges and low fruit water content might be responsible for the disorder.     

Root morphology and the effect of rootstocks on leaf nutrient acquisition of Kinnow mandarin (Citrus nobilis Loureiro × Citrus reticulata Blanco)

The study aimed to understand the root morphological character of 1 year old seedling rootstock of citrus genotypes viz., rough lemon, Karna Khatta, Carrizo citrange, Rangpur lime, Troyer citrange, Jatti Khatti and sour orange as well as to investigate the effect of these rootstocks on the leaf mineral composition of Kinnow. Root morphological traits showed significant genotypic variation. Rough lemon seedlings had a higher root length, projected area, surface area, volume and the number of forks. Sour orange was moderate rootstock of the 7 genotypes for most of the root morphological characters, while citrange rootstocks expressed poor root morphology. The rootstocks also imparted significant influence on the leaf mineral composition. Leaf K, Ca and Mg content was recorded maximum in plants grown on rough lemon seedling, while N, P, Fe, Zn, Mn and Cu concentration was higher on sour orange rootstock. Kinnow trees on Rangpur lime rootstock accumulated more Na in their leaf tissue, where as Troyer citrange restricted the accumulation of Na. Considering the root morphological characters and nutrient accumulation pattern, rough lemon and sour orange for areas free from tristeza virus could be suggested as alternative rootstocks for the studied Kinnow mandarin under similar ecological conditions.     

Production of mandarin + pummelo somatic hybrid citrus rootstocks with potential for improved tolerance/resistance to sting nematode

Sting nematode (Belonolaimus longicaudatus Rau) has become a primary factor limiting citrus production in localized regions of the central Florida sandridge citrus production area, making the development of resistant rootstocks a new breeding objective. In efforts to develop a replacement rootstock for the widely adapted sour orange, our focus has been on somatic hybridization of selected mandarin + pummelo combinations [Grosser, J.W., Gmitter, Jr., F.G., 1990. Protoplast fusion and citrus improvement. Plant Breed. Rev. 8, 339–374; Ananthakrishnan, G., Calovic, M., Serrano, P., Grosser, J.W., 2006. Production of additional allotetraploid somatic hybrids combining mandarins and sweet oranges with pre-selected pummelos as potential candidates to replace sour orange rootstock. In Vitro Cell. Dev.: Plant 42, 367–371], since sour orange is probably an introgression hybrid of mandarin and pummelo as suggested by molecular marker analyses [Nicolosi, E., Deng, Z.N., Gentile, A., La Malfa, S., Tribulato, E., 2000. Citrus phylogeny and genetic origin of important species as investigated by molecular markers. Theor. Appl. Genet. 100, 1155–1166; Gulsen, O., Roose, M.L., 2001. Lemons: diversity and relationships with selected Citrus genotypes as measured with nuclear genome markers. J. Am. Soc. Hort. Sci. 126, 309–317]. Somatic hybrid plants were produced from four new mandarin (C. reticulata Blanco) + pummelo (C. grandis L. Osbeck) parental combinations by fusing embryogenic suspension culture-derived protoplasts isolated from selected mandarins with leaf protoplasts of pummelo seedlings previously selected for tolerance/resistance to the sting nematode (B. longicaudatus Rau) as follows: Amblycarpa mandarin + ‘Liang Ping Yau’ (seedling) pummelo seedling SN7; Amblycarpa mandarin + ‘Hirado Buntan Pink’ (HBP) pummelo seedling SN3; Murcott tangor + pummelo seedling SN3; and Shekwasha mandarin + pummelo seedling SN3. Somatic hybridization was verified by ploidy analysis (via flow cytometry) and RAPD analyses. Mandarin parents were selected for wide soil-adaptation and ability to produce friable embryogenic callus lines. Pummelo seedlings used as leaf parents were identified from a previous screen of large seed populations (200 each) from four pummelos for resistance to sting nematode as follows: ‘Hirado Buntan Pink‘; ‘Red Shaddock‘; ‘Large Pink Pummelo’ and a seedling pummelo of ‘Liang Ping Yau‘. Ten resistant/tolerant pummelo seedlings were selected from the 800 pummelo seeds planted in the screen for further study. The four new somatic hybrids have been propagated to evaluate their horticultural performance and resistance to the sting nematode. These potential somatic hybrid rootstocks should also have potential to control tree size due to polyploidy.     

Agrobacterium tumefaciens-mediated genetic transformation and plant regeneration from a complex tetraploid hybrid citrus rootstock

Agrobacterium-mediated genetic transformation of a tetraploid “tetrazyg” citrus rootstock selection ‘Orange #16’ [Nova mandarin (Citrus reticulata Blanco) + Hirado Buntan pummelo (Citrus grandis L. Osbeck)] × [Cleopatra mandarin (C. reticulata Blanco) + Argentine trifoliate orange (Poncirus trifoliata (L.) Raf.)] was performed. Juvenile epicotyl segments were transformed with a construct containing a bifunctional egfp–nptII fusion gene under the control of an enhanced double CaMV 35S promoter. Our protocol resulted in a reasonable transformation efficiency of 18%. Stable integration of the transgene was confirmed by visual observation of EGFP expression, PCR and Southern blot hybridization. The purpose of this work was to investigate the amenability of novel citrus rootstock germplasm being developed for improved tree size control, soil adaptation, and disease resistance, to existing transformation technologies. Seed trees of such transgenic tetraploids also have potential as trap plants containing potent insecticidal transgenes, due to their inedible fruit and inherent crossing barriers with conventional commercial diploid scion cultivars, and could be planted around producing citrus groves.     

不同柑橘砧木对锦橙果实品质的影响

 2006—2008年连续3年研究11种砧木对铜水72-1锦橙果实品质的影响。结果表明：不同砧木对果实颜色和内在品质均有影响,其中以卡里佐枳橙为砧的果实亮度最好,黄色度值最高,果实最大,果皮最薄;以路比枳为砧的果实红色度值和固酸比（TSS/TA）最高,果皮最厚;以沃尔卡姆为砧的亮度最差,黄色度值、单果质量和可食率最低,中心柱最小;以C35枳橙为砧的中心柱最大且维生素C含量最低;以光皮酸橙为砧的果实红色度最低而可食率最高;以里其16-6枳为砧的果实可溶性固形物（TSS）含量最高;以孙楚沙橘为砧的果实可滴定酸（TA）和维生素C含量最高,而TSS/TA最低;果实TSS和TA最低的砧木为枸头橙。品质综合评价,性状表现较好的为孙楚沙橘、卡里佐枳橙和C35枳橙,而表现较差的为兰普莱檬和沃尔卡姆柠檬。     

Performance of Marsh Seedless Grapefruit on Six Rootstocks in Cyprus

Yield, fruit quality, growth and the levels of 12 elements in the leaves were measured for 12-year-old Marsh Seedless grapefruit trees on six rootstocks. Trees on rough lemon and Cleopatra mandarin were larger than those on sour orange and consistently produced 67 and 23 per cent more fruit respectively than on sour orange. Trees on Palestine sweet lime, Troyer and Morton citranges were the least productive. Three-year means of total soluble solids ranged from 9·4 per cent for fruit from trees on Palestine sweet lime to 11–2 per cent on Cleopatra mandarin. Fruit size was good on all rootstocks but effects of rootstock on levels of Mg, Na, Cl and B in the leaves were statistically significant.     

沙田柚在不同砧木上的早期表现

供试品种为沙田柚,砧木材料２８个,以酸柚砧作对照,研究了不同砧木上沙田柚树体生长发育,产量的早期表现。经过７年的观察分析,初步认为关云大叶枳,江津大叶枳,多花枳,朱砂柑、摩洛哥酸橙对沙田柚有早结,矮化作用。定植后第３年试花,第４年开始结果,结果最多的是关云大叶枳,株产达４个,树体高度比对照矮１１．８％￣２１．０％,产量比对照高２４０％￣６００％,其余砧木都比对照结果迟。     

Evaluation of citrus somatic hybrids for tolerance to Phytophthora nicotianae and citrus tristeza virus

Somatic hybridization is a biotechnology tool that can be used in citrus breeding programs to produce somatic hybrids with the complete genetic combination of both parents. The goal of this work was to test the reaction of citrus somatic hybrids that may be useful as rootstocks to trunk and root infections caused by Phytophthora nicotianae van Breda de Haan (P. parasitica Dastur) and to citrus tristeza virus (CTV). The somatic hybrids evaluated were ‘Caipira’ sweet orange (Citrus sinensis L. Osbeck) + ‘Rangpur’ lime (C. limonia Osbeck), ‘Caipira’ sweet orange + ‘Cleopatra’ mandarin (C. reshni hort. ex Tanaka), ‘Caipira’ sweet orange + ‘Volkamer’ lemon (C. volkameriana V. Ten. & Pasq.), ‘Caipira’ sweet orange + rough lemon (C. jambhiri Lush.), ‘Cleopatra’ mandarin + ‘Volkamer’ lemon, ‘Cleopatra’ mandarin + sour orange (C. aurantium L.), ‘Rangpur’ lime + ‘Sunki’ mandarin (C. sunki (Hayata) hort. ex Tanaka), ‘Ruby Blood’ sweet orange (C. sinensis L. Osbeck) + ‘Volkamer’ lemon, ‘Rohde Red’ sweet orange (C. sinensis L. Osbeck) + ‘Volkamer’ lemon, and ‘Valencia’ sweet orange + Fortunella obovata hort. ex Tanaka. For P. nicotianae trunk and root infection assays, plants of the somatic hybrids, obtained from 9-month semi-hardwood cuttings, were evaluated and compared with diploid citrus rootstock cultivars after mycelia inoculation in the trunk or spore infestation in the substrate, respectively. ‘Cleopatra’ mandarin + sour orange, ‘Rangpur’ lime + ‘Sunki’ mandarin, ‘Cleopatra’ mandarin + ‘Volkamer’ lemon, ‘Ruby Blood’ sweet orange + ‘Volkamer’ lemon, ‘Rohde Red’ sweet orange + ‘Volkamer’ lemon, and ‘Caipira’ sweet orange + ‘Volkamer’ lemon had less trunk rot occurrence, whereas the somatic hybrids ‘Cleopatra’ mandarin + ‘Volkamer’ lemon, ‘Cleopatra’ mandarin + sour orange, ‘Caipira’ sweet orange + ‘Volkamer’ lemon, and ‘Caipira’ sweet orange + ‘Rangpur’ lime were tolerant to root rot. For CTV assays, plants of the somatic hybrids along with tolerant and intolerant rootstocks were budded with a mild strain CTV-infected or healthy ‘Valencia’ sweet orange budwood. Differences in average scion shoot length indicated that the hybrids ‘Cleopatra’ mandarin + sour orange and ‘Valencia’ sweet orange + Fortunella obovata were intolerant to CTV.     

不同砧木对先锋橙矿质营养元素含量的影响

在田间试验条件下,观察了12种砧木的先锋橙矿质营养元素含量。在观察的11种营养元素中,不同砧木间除 N、Zn、Mo元素含量无显著差异外,其它元素均达显著或极显著差异。其中微量元素的变幅大于大量元素。植株营养状况以宜昌橙类(除 K)、枳类(除 Fe)和桔类砧木植株的养分含量较高,果实含酸量高的砧木植株养分含量偏低。耐碱砧木主要表现在Fe、Mn及 K、Cu元素含量的差异。     

梁平柚矮化砧木的筛选

供试柚品种为梁平柚,砧木为枳、香橙、宜昌橙和酒饼簕、以酸柚砧为对照。1983年秋嫁接,1984年秋定植。7年观察结果表明,酒饼簕、宜昌橙、枳对梁平柚有矮化作用,其中以酒饼簕最明显。枳砧梁平柚定植后第2年(1986年),有1/3的植株试花,第3年全部开花,结果最多的一株达8个;香橙、宜昌橙、酸柚砧(对照)梁平柚定植后第3年试花;酒饼簕砧梁平柚第5年试花。枳砧梁平柚树高、树冠体积、枝条电阻值、枝条节间长度等均明显低于对照。初步认为,枳是梁平柚比较理想的矮化砧木。     

世界柑橘品种改良的进展

 柑橘鲜食品种的发展趋势是容易剥皮、无核、有香味和风味浓。过去30年, 通过芽变选种、杂交育种等途径, 全世界培育出了上百个柑橘品种。芽变选种获得的新品种主要来自如温州蜜柑、脐橙和克里曼丁橘, 它们分别形成了品种群, 不同品种采收期可长达4～6个月; 杂交育种途径培育出70多个品种(系) , 主要利用了单胚性品种克里曼丁橘、胞质雄性不育的温州蜜柑以及外观色泽好的红橘等作为杂交亲本; 新的砧木品种(系) 主要来自中国的枳与酸橘等品种的杂交; 加工品种的选育相对落后。生物技术, 特别是胚抢救及细胞融合等技术大大加快了柑橘育种步伐。     

Chloride and sodium excluding capacities of citrus rootstock germplasm introduced to Australia from the People's Republic of China

The responses to root zone salinity (0, 25 and 50 mM NaCl) by 40 citrus rootstock genotypes introduced from the People's Republic of China, measured as shoot chloride (Cl⁻) and sodium (Na⁺) ion accumulation, growth and dry matter accumulation, were investigated under glasshouse conditions. Two experiments, one using aerated nutrient solutions and the other irrigated sand cultures, were conducted with plants grown from rooted cuttings taken from representative trees of different mandarin (Citrus reticulata Blanco and C. erythrosa Hort. ex Tan.), yuzu (C. junos Sieb. ex Tan.), Ichang papeda (C. ichangensis Swing.), sour orange (C. aurantium L.) and trifoliate orange (Poncirus trifoliata (L.) Raf.) genotypes. Two standard genotypes, viz. Rangpur lime (Citrus x limonia Osbeck.) and William's trifoliate orange were included in the experiments as reference controls.     

两种砧木对砂糖橘磷素累积消耗量的影响

采用以酸橘、枳为砧木的成年砂糖橘树作为供试材料,通过对各器官各部位磷素营养水平的分析,研究磷素累积消耗的特点与规律。结果表明：1、砂糖橘不同器官的磷素累积消耗量存在差异,以枝条的累积消耗量最大;除枝条外,不同砧木砂糖橘的相同器官中磷素累积消耗量差异不显著。2、两种砧木砂糖橘地上部的磷素累积消耗量均显著地高于地下部。3、砂糖橘地上部和地下部各器官不同部位的磷素累积消耗量存在一定差异,但不同砧木对地上部和地下部器官各部位的磷素累积消耗量影响不大。4、砂糖橘各级侧枝木质部与韧皮部的磷素累积消耗量存在一定差异,不同砧木砂糖橘之间也不相同。     

Evaluation of rootstocks for the Cyprus local lemon variety ‘Lapithkiotiki’

The effect of various rootstocks on yield, yield efficiency, tree size and fruit quality of the local lemon variety ‘Lapithkiotiki’ (Citrus limon (L.) Burm. F.) was studied under Cyprus conditions. Total cumulative yield over 13 years of production was the highest on rough lemon (C. jambhiri Lush) followed by that on Volkameriana (C. volkameriana Ten. & Pasq.), Yuma Ponderosa lemon (C. limon (L.) Burm. F.), sour orange (C. aurantium L.), Citrus macrophylla Wester, Morton citrange (C. sinensis cv. Washington navel × Poncirus trifoliata (L.) Raf.), Yuma citrange, Rangpur lime (C. limonia Obs.), Palestine sweet lime (C. limettioides Tan.), C-32 citrange and Citremon 1449 (C. limon × P. trifoliata), although no statistically significant differences were found between sour orange, the commercial rootstock used in Cyprus, and the other above mentioned rootstocks. Next in order as regards to total cumulative yield was Cleopatra mandarin (C. reticulata Blanko.) followed by Carrizo citrange, with statistically significant differences compared with sour orange. Trees on Citrumelo CPB-4475 (C. paradisi Macf. × P. trifoliata) and C-35 citrange died 3–4 years after grafting. Canopy volume was the lowest for trees on Cleopatra mandarin and Carrizo citrange. Yield efficiency A, expressed as total cumulative yield per trunk cross-sectional area, was the highest on C. macrophylla and lowest on Carrizo citrange. Rootstock significantly affected fruit size and weight, rind thickness, juice content, brix, total acids and brix:acid ratio. The results of the present study reveal that the most promising rootstocks that may replace sour orange for the local lemon variety ‘Lapithkiotiki’ under Cyprus conditions are Volkameriana, Yuma Ponderosa lemon, C. macrophylla and Citremon 1449.     

Facultative apomixis and chromosome doubling are sources of heterogeneity in citrus rootstock trials: Impact on clementine production and breeding selection

All commercial citrus rootstocks are polyembryonic and propagated by seeds. Although these seeds produce uniform plant material most of the time, zygotic or polyploid citrus seedlings may arise. The aim of this study was to understand how zygotic or tetraploid rootstock could affect a citrus rootstock selection field trial. A trifoliate orange selection field trial, which was planted in 1974 and grafted with clementine, was re-investigated with respect to the presence of rootstocks that were not true-to-type. Among the 288 trees investigated, flow cytometry identified 2.4% of rootstocks as tetraploid and SSR markers indicated that 6.6% were zygotic. Yield data showed that the presence of tetraploid rootstock dramatically decreased (by about 45%) clementine fruit production. However, zygosity did not always affect fruit production and a range of effects were observed, from a slight increase in production to a 24% decrease. Exclusion of non-true-to-type genotypes from the production analysis indicated that the best candidate for rootstock was a clone previously ranked in the middle of the 32 rootstocks under evaluation. However, the presence of zygotic rootstock did not appear to cause any significant differences in fruit quality during the first 5 years of the investigation, which suggests that non-true-to-type plants cannot be identified by fruit quality parameters. This study indicates that tetraploid and zygotic rootstocks have a strong impact on citrus fruit production in orchards, and removal of off-type seedlings is required prior to planting in any agronomic trial.     

3种柑橘实生砧木及其2种体细胞杂种根系解剖结构的比较

采用石蜡切片法和组织离析法分别对3种柑橘实生砧木和2种体细胞杂种的根系木质部和导管分子的解剖构造进行了比较。结果表明：（1）粗柠檬、红橘和枳3种实生砧木根系的木质部和韧皮部呈同心圆环状排列,而‘红橘+枳’和‘红橘+粗柠檬’两种体细胞杂种木质部和韧皮部呈“海星状”排列,结构异常。（2）导管所占的面积和密度,均以生长势较强的粗柠檬为大,以生长势较弱的枳为小;体细胞杂种没有明显规律。（3）柑橘导管分子属于孔纹导管,穿孔板均为单穿孔,大多分布于端壁上;导管分子两端具尾、倾斜、侧壁穿孔等性状的有无及其比例,反映出生长势的差异及其输导能力的强弱。（4）粗柠檬具有较好输导能力的导管分子结构,而枳较差;体细胞杂种根系的导管分子长度和直径都大于其亲本,在导管分子性状上,向不利于输导能力的较原始性状偏移。     

靠接换砧矫治枳砧甜橙缺铁黄化研究

靠接红桔、酸桔和枸头橙砧,矫治枳砧甜橙缺铁黄化有明显效果。其中,以枸头橙效果最好,以下依次为酸桔和红桔,靠接砧苗后树势逐年恢复,产量成倍增加,靠接红桔、酸桔和枸头橙分别比对照增产3.3、1.4和1.5倍;对提高果实含糖量、果汁率和降低含酸量亦有良好效果。     

Long-term performance of ‘Ellendale’ mandarin on seven commercial rootstocks in sub-tropical Australia

‘Ellendale’ mandarin (Citrus reticulata Blanco) on seven commercially important rootstocks was assessed over a 26-year period on a site not previously planted to citrus. Tree yield data collected each season from 1969 to 1991 showed that yields were highest on ‘Lockyer’ rough lemon (C. jambhiri Lush) and lowest on ‘Emperor’ mandarin. Yields for the two citranges (C. sinensis (L.) Osbeck × Poncirus trifoliata (L.) Raf.), ‘Troyer’ and ‘Carrizo’, were intermediate, and somewhat higher than those for two selections of sweet orange (C. sinensis (L.) Osbeck), ‘Parramatta’ and ‘Joppa’. Linear regression was used to examine changes in yielding pattern across the 23 seasons of fruit production. This revealed that ‘Troyer’ was comparable with the rough lemon selections throughout most of the experiment and significantly higher than ‘Carrizo’ during certain periods in the middle of the experiment. Similarly, while ‘Joppa’ and ‘Parramatta’ produced near-identical results during most of the experiment, ‘Joppa’ out-performed ‘Parramatta’ toward the end of the experiment. ‘Emperor’ showed a low yield trend throughout the experiment, often more than 50 kg per tree per year less than the rough lemon and citrange selections. Detailed assessment of biennial bearing showed a significant pattern commencing when trees were approximately 15 years old and intensifying until the end of the experiment. However, rootstock had no effect on the biennial bearing behaviour of ‘Ellendale’ mandarin. Correlations of cumulative yields at each harvest date with the final cumulative yield (for 23 seasons of cropping) showed instability up until approximately the eighth year of cropping after which it increased steadily, suggesting that in similar experiments there may be only marginal value in assessing yields beyond about the 10th season. Fruit quality assessments made in two consecutive seasons showed expected trends, with rough lemon (both ‘Lockyer’ and ‘Mazoe’) producing the largest and heaviest fruit, with thicker rinds, lower juice content, and lower Brix. The citrange selections (‘Troyer’ and ‘Carrizo’) resulted in fruit quality comparable to the sweet oranges (‘Parramatta’ and ‘Joppa’), with ‘Troyer’ producing significantly higher Brix levels than any other rootstock. All rootstocks produced leaf nutrient levels close to the desirable range, with significant differences for the elements P, Mg, Ca, Mn, and B. These differences separated the seven rootstocks into categories consistent with their genetic relatedness.     

柑橘砧木对酸碱耐性的评价

中国南方许多地区因土壤pH值偏高或偏低,严重影响柑橘的产量和质量。筛选适合不同pH环境的优良砧木对改善柑橘的生产条件具有重要意义。以扁平橘、朱橘、汕头酸橘、枸头橙、卡里佐枳橙、尼8047、道县野橘和聂都野橘等8种柑橘砧木实生苗为试验材料,在酸性(pH 3.5)和碱性(pH 9.0)营养液栽培条件下调查叶片症状并测定叶片中与抗逆性紧密相关的丙二醛、可溶性蛋白、脯氨酸含量和超氧化物歧化酶、过氧化物酶、过氧化氢酶活性等指标,通过聚类和隶属函数分析,综合评价不同砧木对酸、碱的耐性。分析结果表明:叶片表型症状的观察结果与生理生化指标分析结果基本一致;在酸性(pH 3.5)条件下,汕头酸橘、尼8047和扁平橘表现出较强的耐性,聂都野橘和道县野橘较为敏感;在碱性(pH 9.0)条件下,朱橘、枸头橙和扁平橘表现出较强耐性,而聂都野橘和道县野橘的耐性较弱。扁平橘在酸、碱环境下均表现出较强的适应性,是一个具有一定应用潜力的优良砧木。