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The article presents the results of research of the chemical composition of easily volatile components in the leaves of nine taxa representing species and varieties of the genus Citrus L. cultivated under the conditions of greenhouses of the Central Botanical Garden of the National Academy of Sciences of Belarus as: C. unshiu (Tanaka ex Swingle) Marcow., C. grandis Osbeck cv. Bogatyr, C. sinensis Osbeck cv. Washington Navel, C. medica L. cv. Sarcodactilis, C. medica cv. Pavlovskiy Shishkan, Lemon Skernevitsky (’Ponderosa lemon’) is a clone of the hybrid C. medica L. × C. limon (L.) Burm. f., Citrofortunella microcarpa, C. limon (L.) Osbeck cv. Pavlovskiy, C.meyeri (Ju. Tanaka). The volatile components were extracted using a Supelco™ solid-phase microextractor placed in the vapour-air space above air-dried, finely ground and heated to 40 °C leaf samples. The component composition of the extracts was analyzed by the GC/MS method using the Agilent Technologies 6850 Series II system (Network GC System/5975B (VL MSD). Total 36 components were identified in the leaves of citrus plants: monoterpenes (14), sesquiterpenes (11), and oxygen-containing compounds: terpene alcohols, aldehydes, ethers (11). The studies have shown that the cyclic hydrocarbons monoterpene (Z)-β-trans-Ocimene and 3 sesquiterpenes (β-caryophyllene, (3E, 6E)-α-farnesene, and α-caryophyllene) were detected in the volatile components in leaves in the whole citrus group. While 2 sesquiterpenes: (3E,6E)-α-farnesene and α-caryophyllene are dominant for the most taxa based on their proportions in the total volume of volatile compounds. Sesquiterpene beta-Elemene is present as a dominant component exclusively in species and varieties representing the so-called “sweet citrus” group as it follows from the results of the studies: C. unshiu, C. grandis cv. Bogatyr, C. sinensis× cv. Washington Navel, C. meyeri, which allows one to consider it as a significant feature in the taxonomy of the genus Citrus L.

In October 2015, a Mexican lime exhibiting citrus canker symptoms was found by the USDA APHIS PPQ in a residential property in Rancho Viejo, Cameron County, Texas. Real-time PCR analysis detected the presence of Xanthomonas citri subsp. citri; USDA APHIS PPQ in Beltsville, MD confirmed this diagnosis. A delimiting survey was initiated and suspect leaf samples were collected and sent to the PPQ Beltsville lab for analysis. By October 2017, leaf samples from 197 trees were confirmed positive for citrus canker, all within a 5-mile radius; in addition, a further 59 symptomatic trees were found and all 256 infected trees (254 Mexican lime, one makrut lime, and one Ponderosa lemon) were removed. Survey data collected on stem lesions suggested the oldest lesions to be between 4 to 6 years old. A host-range study using 12 citrus varieties, including the major commercial varieties grown in Texas, were inoculated with crude leaf extracts from symptomatic leaves by leaf infiltration method. Mexican limes and alemow were the only citrus plants that developed definitive canker lesions. A combination of host range, serological, and molecular tests suggested that this isolate was different from the typical Asiatic strain and more similar to X. citri subsp. citri AW which was only previously reported from Florida on Mexican lime and alemow.

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.

1 - A presente contribuição refere-se aos trabalhos iniciais para o estabelecimento, na Estação Experimental de Limeira, de experiências sobre cavalos para as principais variedades cítricas comerciais no Estado de São Paulo, isto é, as laranjas Baianinha e Pera e o pomelo Marsh-seedless. 2 - Nessas experiências estão em estudo 12 variedades-cavalo pertencentes a 2 gêneros e 8 espécies. 3 - Ligeiras referências são feitas sobre as 12 espécies e variedades-cavalo, algumas das quais ainda não foram utilizadas no Estado, para tal fim. 4 - Citam-se dados sobre o número de sementes, germinação, poliembrionia e desenvolvimento relativo na sementeira. 5 - O desenvolvimento no viveiro, antes e depois da enxertia, se baseia em medições feitas de tempos a tempos, a princípio nos cavalos (altura) e depois nos cavalos e enxertos (circunferências da haste). 6 - As últimas medições feitas no viveiro, mostram que há comportamento significantemente diferente entre as 12 espécies e variedades-cavalo experimentadas, considerando-se os seus respectivos desenvolvimentos. 7 - No viveiro sobressaíram, por mais rápido crescimento, as seguintes espécies e variedades-cavalo : lima da Pérsia, limão rugoso, limão cravo, limão ponderosa e cidra. O trifoliata, as laranjas lima e caipira, e a tangerina cravo foram de crescimento mais lento, enguanto as laranjas azeda e agro-doce e o pomelo ocuparam posição média. 8 - Instalou-se a experiência definitiva com a transplantação das mudas, em 1936, para o lugar definitivo (pomar), formando-se 6 quadras (4 blocos e 24 parcelas cada uma). 9 - O plano destas experiências comporta observações sobre : a) Desenvolvimento das plantas b) Produção (frutos) qualitativa e quantitativa c) Suscetibilidade a moléstias e pragas d) Interação entre cavalos e enxertos e) Longevidade das plantas.1 - The present paper deals with the first results of an extensive study on the relations between stock and scion in Citrus, in progress at the Experiment Station of Limeira, of the Instituto Agronômico of Campinas, São Paulo, Brazil, since 1933. 2 - All the scions used belong to three commercial varieties : Baianinha (orange, derived from "Washington Navel"), Pera (orange, similar to Valencia) and Pomelo (grape-fruit "Marsh-seedless") were collected in each case from one individual of each type. 3 - The following 12 stock were studied : Laranja azeda (sour orange) Laranja agro-doce (bitter sweet orange) Laranja caipira (sweet orange) Laranja lima (sweet orange) Tangerina cravo (tangerine) Limão cravo (Rangpur lime) Limão rugoso (rough lemon) Limão ponderosa (ponderosa lemon) Lima da Pérsia (sweet lime) Pomelo (grape-fruit Triumph) Cidra (citron) Trifoliata (Poncirus trifoliata). All plants obtained came from seeds of one tree of each type, from unprotected flowers however. 4 - Data referring to the number of seeds per fruit, germination, polyembriony and classification according to size are given (quadro I). The mean height of the plants obtained after 6 months and 2 years nursery are to be found in quadro II. 5 - Twelve hundred individuals of each root stock were selected according to their uniform development, in accordance with Webber (25) and on 40 of each buds of the three scions were grafted. As measure of the development the circumference of the stock at a height of 20 cm and that of the scion at a height of 40 cm were used (quadros IV to IX). 6 - An analysis of variance "between" and "within" root stocks (quadro VI) showed in all cases a significant high variation "between" stock. In all cases, the scions were thinner than the stocks (quadro IX), the indices scion-stock varying from ca. 0,5 to 0,8. The respective means are to be found in quadro IV and V. 7 - There is also a consistent and significant difference between scions as shown by the values in quadro VII. 8 - A comparison between quadro VIII (not budded root stock) and quadro IV (budded) shows that generally the former grow better. They are however some exception to this rule, especially in "Tangerina cravo". 9 - All the observation reported so far were made in the nursery, but the detailed lay-out of the experiment in the orchard is also described. Lots of 4 or 9 plants of each combination were arranged in four complete random replications. The trees supported the planting out very well, only Citron replantings being necessary. The trees are now fully matured and produced already during 3 years. The results of the first five years of the experiment with trees in the orchard, including the analysis of their yields, will be given in a future publication.

THE isolation and structure of citronin, a new flavanone glycoside from the peel of immature Ponderosa lemons (Citrus limon Burm. f. ponderosa Hort.) was reported some time ago by Yamamoto and Oshima1. From chemical and spectroscopic evidence it was concluded that citronin is 2′-methoxy-5,7-dihydroxyflavanone 7-rhamnoglucoside (I) and thus belongs to the rather uncommon group of flavonoids having a substituent at position 2′. In attempting to obtain this compound from samples of both mature and immature Ponderosa lemons, under conditions approximating those of Yamamoto and Oshima, it has been our experience that the only glycoside which can be isolated easily in crystalline form is neohesperidin (II). This was identified by elementary analyses, mixed melting point determination, infra-red spectrum, preparation of the phenylhydrazone derivative and isolation of the aglycone hesperetin from the hydrolysate. Neohesperidin differs from hesperidin only in the position of attachment of rhamnose to glucose2