SELECTION OF NEW PROMISING SEEDLESS MANDARINS TRIPLOID HYBRIDS FROM CROSSES BETWEEN MONOEMBRYONIC DIPLOID FEMALE AND DIPLOID MALE PARENTS

Morocco is one of the major exporters of small citrus fruits, such as mandarin and Clementine. Seedlessness is a major criterion for this horticultural group. The present study focused on the selection of the best triploid mandarin hybrids (2n=3x=27) characterized by seedless fruits. A series of crosses between ‘Sidi Aissa’ clementine (female parent) and seven mandarin varieties (‘Lee’, ‘Wilking’, ‘Osceola’, ‘Carvalhal’, ‘Satsuma Frost’, ‘Satsuma Owari’ and ‘Chienka’) was performed by the National Institute for Agricultural Research. Forty triploid mandarins were obtained and planted since 2002 in an experimental field at El Menzeh. Varietal evaluation was focusing on fruit quality traits during seven years. Statistical analyzes showed that there is a significant difference for all studied characters and between hybrids. The number of seeds per fruit is the main criterion which differentiates between triploids mandarin’s hybrids and their diploid parent “clementine Sidi Aissa”. The best hybrids selected were: HT11, HT13, HT27, HT43, HT44, and HT49. The best crosses are C1 (‘Sidi Aissa’ × ‘Wilking’) andC2 (‘Sidi Aissa’ בOsceola’). These promising triploid hybrids of mandarin have been multiplied on several rootstock trials and are in the process of quantitative evaluation and multi-site testing

Effet de la nutrition azotée sur les paramètres morphologiques et physiologiques de quelques portegreffes d’agrume

Introduction: In Morocco, the sour orange is the rootstock the mostly used in citrus orchard. This position is acquired because of its good adaptation vis-à-vis the Moroccan soil conditions of the regions characterized by the high alkalinity and salinity. However, the spread of CTV in the Mediterranean Basin will soon prohibit the use of traditional rootstock (sour orange). Therefore, the profile of plant material used for the planting of new citrus orchards is changing. To date, studies dealing with the optimization of nitrogen fertilization and selection of the most efficient rootstock in terms of nitrogen use in the production of citrus plants in good quality at the nursery are very important. To finalize the selection of rootstocks revealing performance in terms of adaptation to soil and climatic conditions, their evaluation on the efficiency of input use is of paramount importance. Objective: The main objective of this study is the evaluation of the alternative rootstocks to sour orange (Citrus aurantium L.) in terms of nitrogen usage. Material and methods: This study was carried out in greenhouses at the Experimental station of El Menzeh INRA Morocco. The six rootstocks tested are: citrange Carrizo, citrange C35, Citrus volkameriana B2 28613, Citrus macrophylla, Citrumelo 4475 AB6 A4 and sour orange (Citrus aurantium L.). These seedlings rootstocks aged three months were grown in plastic pots (3L). Nitrogen was added to the nutrient solution modified Hoagland and Arnon (1950), at four doses: T1 (0 mM of N), T2 (1 mM N), T3 (5 mM N) and T4 (10 mM N) for each rootstock. Different doses of nitrogen were applied once a week over a period of three months at 0.5 liter per plant. The experimental design adopted was a split-plot design with three replications. Results: The results of this study showed that there is variability in response between the rootstocks studied vis-à-vis the nitrogen.Citrus volkameriana B2 28613, Citrus macrophylla and Citrumelo 4475 AB6 A4 recorded the highest values of number of leaves per plant, diameter of the collar, the final height of the stem, total leaf area and fresh and dry weight of different organs (stem, leaves and root). Citrus volkameriana B2 28613 and Citrus macrophylla showed the highest percentages of relative water content. The rootstock Carrizo citrange showed the highest content of total chlorophyll (SPAD) and total soluble sugars (TSS). Also, Citrus macrophylla had the stomatal conductance and concentration of the highest total chlorophyll in leaves. Citrus volkameriana B2 28613 and Citrus macrophylla have accumulated higher levels of nitrogen in leaves. Conclusion: Citrus volkameriana B2 28613, Citrus macrophylla and citrumelo 4475 AB6 A4 rootstocks are most efficient in terms of nitrogen use in the nursery stage and that the dose T3 (5 mM of N) proved to be optimal for the production of good quality plants to rootstocks at nursery stage

Évaluation de la résistance de dix porte-greffes d’agrumes résistants à la tristeza vis-à-vis du déficit hydrique

Introduction. In Morocco, citriculture faces up an increasing combination of biotic (Citrus tristeza virus (CTV) / Phytophthora spp.) and abiotic stresses (salinity, alkalinity and drought). Most of these constraints should be individually managed by adapted rootstock choice. However, the spread of CTV in the Mediterranean Basin will soon prohibit the use of the traditional sour orange rootstock, which currently provides sufficient tolerance to salinity and alkalinity. Therefore, the selection of new citrus rootstocks becomes urgent. Our study sought to investigate the effect of different water regimes on growth of ten citrus rootstocks: citrange Carrizo (France), citrange Carrizo (Morocco), citrange Troyer, citrange Yuma, Citrus volkameriana; two Poncirus trifoliata of different origins, citrumelo, Mand. Sunki x Poncirus trifoliata, and Poorman. Materials and methods. For each rootstock, three months old seedlings were grown in plastic pots (0.5 L) in a greenhouse at El Menzeh, INRA, Morocco; they were subjected to three water regimes [(100%, 75% and 50%) moisture field capacity (Hcc) of the substrate]. The experiment was arranged in a split-plot design with three treatments. The morphological parameters measured were the plant height and dry and fresh matter accumulation. Physiological parameters studied were the Relative Water Content, transpiration rates and chlorophyll, soluble sugars and proline contents. Results. The morphological and physiological parameters were affected by the intensity of water stress applied. However, rootstocks behaved differently regarding to this constraint. Water stress induced an increase in the proline and soluble sugars content in the rootstock leaves. Conclusion. Water stress significantly affects the physiological and morphological characteristics of citrus rootstocks and, in conditions of extreme water deficit (50% Hcc), a differential behavior of the rootstock was found. Based on our results, the rootstocks Carrizo citrange (Morocco) and Poorman present the best overall ability to withstand water stress

Caractérisation morpho-pomologique de 23 accessions de citronnier de la collection El Menzeh de l’INRA Maroc

INRA Morocco has an important citrus collection located in several sites in the Kingdom. Citrus germplasm offers a large resource for selecting within local lemon accessions of genes related to disease resistance, stress, production, fruit quality. Which are essential for genetic improvement. Some potential varieties may be of interest to producers. In the present study, twenty-three accessions of a lemon tree (Citrus limon [L.] Burm. F.) planted at El Menzeh collection, are characterized according to the IPGRI and UPOV citrus descriptors. Morpho-pomological variables showed a significant difference between lemon accessions. Only the morphological parameters of leaves, fruits and fruit peel color showed a high variability. Chemical analysis of the juices revealed significant differences among accessions. The data showed that acidity ranged from 0.1% for Sweet and Butnal lemons to 6.6% for Kennedy. While, the Kerkachi, Butnal, Cascade and Allen lemon accessions had the highest levels of both sugar and juice. Likewise, the accessions Doux Acid, Dellys and Kennedy showed fruits with an important size. The fruits of Lisbon, Eureka, Corregia, Ba Ahmed and Valencia had fruits with a low number of seeds or seedless. Our study showed that there was an acceptable pomological variability among the accessions of lemons cultivated in Morocco. Butnal, Allen, Cascade, Sçweet Acid, Dellys, Kennedy, Lisbon, Eureka, Corregia, Ba Ahmed and Valencia lemons were promising in terms of quality. This makes them an important genetic resource for any future lemon program to expand varietal diversification for improved productivity and competitiveness of citrus. Finally, the use of molecular markers is necessary to complete this work and for better differentiation of closely related individuals.L’INRA Maroc dispose d’importantes collections d’agrumes localisées au niveau de plusieurs sites du royaume. Le germoplasme des agrumes offre une large gamme ressource de gènes liés à la résistance aux maladies, aux stress, à la production, à la qualité des fruits, etc., essentiels pour l’amélioration génétique. Certaines variétés potentielles pourraient intéresser les producteurs. Dans la présente étude, vingt-trois accessions de citronnier (Citrus limon [L.] Burm. F.) plantées au niveau de la collection d’El Menzeh, ont été caractérisés sur la base de la morphologie des feuilles, des fleurs et des fruits, à l’aide de descripteur prescrit pour les agrumes par (IPGRI) ‘International Plant Genetic Resources Institute’ et de l’Union de Protection des Obtentions végétales (UPOV). Les résultats de l’analyse de la variance des variables morpho-pomologiques ont montré une différence significative entre les accessions. Seulement les paramètres morphologiques des feuilles, des fruits ainsi que la couleur de l’écorce du fruit ont montré une variabilité élevée. De même, l’analyse chimique des jus a révélé des différences significatives entre les accessions. Les données ont démontré que l’acidité variait de 0,1 % pour les citrons Doux et Butnal à 6,6 % pour Kennedy. Tandis que les accessions de citrons Kerkachi, Butnal, Cascade et Allen présentaient les teneurs les plus élevées aussi bien en sucre qu’en jus. De même, les accessions Doux acide, Dellys et Kennedy montraient des fruits avec un calibre important. Enfin, les accessions Lisbon, Eureka, Corregia, Ba Ahmed et Valence possédaient des fruits avec un faible nombre de graines voir nul. Notre étude a démontré qu'il existait une variabilité pomologique acceptable parmi les accessions de citrons cultivés au Maroc. Les citrons Butnal, Allen, Cascade, Doux acide, Dellys, Kennedy, Lisbon, Eureka, Corregia, Ba Ahmed et Valence étaient prometteur en termes de qualité. Ce qui en fait une ressource génétique importante pour tout programme futur concernant les citrons pour élargir la diversification variétale pour amélioration de la productivité et la compétitivité des agrumes. Enfin, l’utilisation des marqueurs moléculaires est nécessaire pour compléter ce travail et pour une meilleure différenciation des individus étroitement apparentés