Feeding and Oviposition Behaviour of Trioza erytreae (Hemiptera: Triozidae) on Different Citrus Rootstock Material Available in Europe

Trioza erytreae (Del Guercio, 1918) (Hemiptera: Triozidae) is a vector of Candidatus Liberibacter spp., the causal agent of Huanglongbing disease (HLB). This study evaluates the preference of T. erytreae in different citrus seedlings. Thus, six different non-grafted citrus rootstocks were used for these experiments: (a) Carrizo citrange; (b) Citrus macrophylla; (c) ‘Cleopatra’ mandarin; (d) Forner-Alcaide No. 5; (e) Forner-Alcaide No. 517, and (f) Poncirus trifoliata (‘Flying Dragon’). The behaviour and survival of this psyllid was evaluated through the feeding preference of T. erytreae adults for different rootstocks (in a choice trial under greenhouse conditions) and oviposition and survival of T. erytreae adults on the different citrus material (in a no-choice trial under laboratory conditions). Trioza erytreae showed a clear preference for hosting and feeding on C. macrophylla, and Carrizo citrange was the most suitable rootstock for insect reproduction and survival followed by C. macrophylla. Conversely, Poncirus trifoliata was the least attractive rootstock to T. erytreae adults in the greenhouse trial and led to significantly lower T. erytreae survival. Our results suggest that conventional citrus rootstocks, such as Carrizo citrange and C. macrophylla, could increase T. erytreae populations.

Substandard and Semi-Dwarfing Citrus Rootstocks for More Intensive, Higher-Density, and Sustainable Plantation Systems

An increasing number of intensive, dense, and sustainable citrus plantations have fostered a growing interest in addressing the future challenges of citrus crops: An increase in the world’s population, climate change, and globalization. Nutrient efficiency and the absence of vigorous citrus rootstocks are required for the success of these plantation systems. The agronomic performances of the “Lane Late” orange cultivar on three substandard or semi-dwarfing citrus rootstocks (Forner-Alcaide no.5 (FA5), Forner-Alcaide no.13 (FA13), and Forner-Alcaide no.41 (FA41)) were evaluated in Spain in comparison with more traditional Mediterranean citrus rootstocks (Carrizo citrange (CA), Citrus macrophylla (MP), and ‘Cleopatra’ mandarin (CL)) under a poor mineral fertilization program over six growing seasons. FA13 and FA41 induced the smallest ‘Lane Late’ trees. Although the rootstock did not induce a significant effect on the ‘Lane Late’ yield efficiency (kg m−3), the highest values were recorded for ‘Lane Late’ on MP, CL and FA13. In this sense, FA13 showed a high productive potential (kg ha−1), given the possibility of narrowing the tree spacing (smaller tree size). Regarding the use of soil nutrients, FA13 was the most efficient citrus rootstock. Thus, FA13 stands out as the most suitable citrus rootstock for more intensive and sustainable plantation systems of the ‘Lane Late’ orange under Mediterranean conditions similar to those of this study.

Plant-feeding may explain why the generalist predator Euseius stipulatus does better on less defended citrus plants but Tetranychus-specialists Neoseiulus californicus and Phytoseiulus persimilis do not

The generalist predator Euseius stipulatus (Athias-Henriot) and the Tetranychidae-specialist predators Neoseiulus californicus (McGregor) and Phytoseiulus persimilis Athias-Henriot play a key role in the regulation of Tetranychus urticae Koch in Spanish citrus orchards. Previous studies have shown that sour orange (Citrus aurantium L.) and Cleopatra mandarin (Citrus reshni hort. ex Tan.) display extreme resistance and susceptibility to T. urticae, respectively. When offered a choice between these two genotypes infested by T. urticae, E. stipulatus preferred Cleopatra mandarin, whereas the specialists did not show any preference. The present study was undertaken to check whether these preferences could be related to the feeding of E. stipulatus on the host plant and/or to differences in prey feeding on the two plants. Our results demonstrate that E. stipulatus is a zoophytophagous mite, which can engage in direct plant feeding in sour orange and Cleopatra mandarin, whereas neither N. californicus nor P. persimilis do so. Whereas Cleopatra mandarin provided a higher-quality prey/feeding substrate for E. stipulatus, which may be related to its phytophagy, no differences were observed for the two specialists. As higher constitutive and faster inducible defense against T. urticae in sour orange relative to Cleopatra mandarin plants result in sour orange supporting lower T. urticae densities and plant damage, our results demonstrate that pest regulation by specialist natural enemies may be more effective when prey feed on better defended plants.

Growth and yield of orange (Washington Navel 141) grafted on different citrus rootstocks

This investigation was conducted during 2014, 2015 and 2016 in the field of the citrus experimental station in Ciano, the general corps of scientific agricultural researches. The growth and yield of orange trees (Washington navel 141) budded on seven citrus rootstocks (Sour orange, Troyer citrange, Carrizo citrange, Citrumelo 4475, Citrumelo 1452, Macrophylla and Cleopatra mandarin) and farmed since 1989 have been studied. The results for the average of yield showed that the trees grafted on Cleopatra mandarin (58.33 kg. tree-1) were significantly superior to those grafted on Macrophylla (34.17 kg. tree-1). Orange trees grafted on Citrumelo 4475 and Citrumelo 1452 were significantly superior to other treatments in trunk section area of the rootstock (922.41 and 841.02 cm2, respectively). The greatest fruit fresh weight was in trees grafted on Citrumelo 4475 (284.85 g. fruit-1) which were significantly superior to those grafted on Carrizo and Troyer citrange (232.49 and 236.06 g. fruit-1, respectively). The biggest total soluble solids (%) was in trees grafted on Carrizo and Troyer citrange (12.83% for both treatments) which were significantly superior to those grafted on Sour orangе and Macrophylla (11.5% for both treatments), while the greatest total acids (%) was by Sour orange (2.08%) without significant differences.

Bazı Turunçgil Anaçlarında Tuza Tolerans için In vitro Testleme

Just because of geographical spread, citrus species generally grow in places sensitive to salinity. Testing methods have a significant role in breeding and cultivar development programs. This study was conducted to investigate in vitro salt response of Cleopatra mandarin (Citrus reshni Tan.), sour orange (Citrus aurantium L.), rough lemon (Citrus jambhiri Lush.), Volkamer lemon (Citrus volkameriana Tan & Pasq.), Carrizo citrange (Poncirus trifoliata L. Raf. X Citrus sinensis L. Osbeck) and trifoliate orange (Poncirus trifoliata Raf.) rootstocks at different NaCl concentrations. Seeds were germinated in MS medium with 0, 45, 90 and 135 mM NaCl concentrations. In general, the greatest germination rates in all salt concentrations in Volkamer lemon and sour orange rootstocks and the lowest values were observed in rough lemon and trifoliate orange rootstocks. Present findings revealed that in vitro conditions could reliably be used in salt tolerance tests of citrus rootstocks.

In vitro study the effect of salinity stress on two citrus rootstock growth (Citrus Aruntium), (Cleopatra Mandarin)

This study was conducted at the plant tissue plant of the Biotechnology Research Center for the purpose of determining the effect ofadding different concentrations of Nacl on the growth and development of the citrus rootstocks (Narang and Cleopramtradrin). Citrus seeds were cultured on MS media supplemented with different concentrations ofNaCL100,80,60,40,20,0 mM. The result showed that citrus rootstocks growth negatively infected by salinity while plant length and number of laves decreased by increasing of salinityfor booth rootstocks .plant length and number of leaves were significantly higher in treatment 0 and 20 mMNaCL compared with other treatments, also the results showed that the plants continued to grow well until 60 mM concentration..

Initial shoot development and root architecture of citrus rootstocks

A well-developed root system is a very important characteristic of rootstocks. Initial plant characterization is a potential technique to highlight cultivars with desirable root architecture for the diversification of rootstocks in the national citriculture. Thus, the aim of this study was to evaluate the initial shoot development and root architecture of citrus cultivars used as rootstocks. Seeds from five rootstocks, ‘Cleopatra’ mandarin, ‘Rangpur’ lime, ‘Rough’ lemon, ‘C13’ and ‘Troyer’ citranges, were sown in black polyethylene bags. A completely randomized block design with five replications and one plant per plot was applied. At 30 and 45 days after emergence, shoots and roots were collected for analysis. Shoot analysis measured the total number of leaves, leaf area, stem diameter, plant height, and fresh and dry matter weights. Root analysis evaluated fresh and dry matter weights and root architecture by image analysis, which recorded root traits including primary, secondary, and tertiary root numbers; length and total volume; and the percentage of secondary roots present in the upper third of the primary root. Shoot and root data of fresh and dry weights were submitted to variance analysis and compared using Tukey’s test (5%). The remaining root data were standardized for variance 1 and studied through principal component analysis. The ‘C13’ citrange showed good shoot development, with greater leaf area, plant height, stem diameter, and shoot fresh and dry matter weights during both evaluation periods, followed by the ‘Troyer’ citrange. The ‘Cleopatra’ mandarin had the smallest shoot and root development during both evaluation periods, presenting lower primary root, secondary root, and root volume than other cultivars evaluated at the same time. The ‘Troyer’ citrange had fewer roots in the upper third of the primary root and a higher root insertion angle.

In vitro Multiplication and Genetic Fidelity Studies in Cleopatra Mandarin (Citrus reshni Tanaka)

The present investigation was undertaken for in vitro multiplication of Cleopatra mandarin using nodal segment explants. Nodal segments taken from 9 years old plant in the month of March - April were cultured on Murashige and Skoog (1962) medium supplemented with BAP 0.5 mg/l + Kin 0.5 mg/l for establishment. Various concentrations of auxins viz. IAA and NAA were used singly or in combination with cytokinins (Kinetin and BAP) for shoot multiplication. Maximum number of shootlets per sprouted bud (8.2 ± 0.22) and maximum length of shootlets (3.0 ± 0.12cm) were recorded when auxins were used in combination with cytokinins at a concentration of NAA 0.3 mg/l + BAP 1.0 mg/l. Full strength MS media fortified with 1mg/l IBA was used for rooting of multiplied shoots and was kept in potting media containing sand, soil and vermi compost in 1:1:1 ratio for hardening.In vitro raised plants were examined for genetic stability by using RAPD primers. Out of fifty primers screened, eleven primers produced amplification while thirty-nine primers did not show any amplification. All RAPD profile for in vitro raised plants were monomorphic and similar to their mother plant, which showed that all the plants raised through micropropagation were true to type.

EFFECT OF FOLIAR APPLICATION SALICYLIC ACID ON CITRUS ROOTSTOCKS TOLERANCE TO SOIL SALINITY

This experiment was carried out at the private nursery located at Baquba city/ Diyala governorate during 2015 agricultural season on three years old Citrus rootstocks seedlings to study the effect foliar application of salicylic acid on seedlings tolerance to soil salinity. The experiment included 24 treatment represented three factors: soil salinity levels (1.14,4.62 and 5.30 dSm-1) , two levels of salicylic acid (0 and 250 mg.l -1) and four citrus rootstocks (Sour orange, Cleopatra mandarin, Volkamariana lemon and Troyercitrange ),and their interactions with three replications . The results showed that: increasing soil salinity reduced most studied growth parameters (number and length of branches, number of leaves and fresh weight of the vegetative and root system). Salicylic acid application caused an increment in number of leaves, fresh and dry weight of root system. Citrus rootstocks Troyercitrange was superior on other rootstocks by giving highest values branches length, whereas Cleopatra mandarin rootstock was superior in the number of leaves.