Huanglongbing (HLB) is the most destructive, yet incurable disease of citrus. Finding sources of genetic resistance to HLB-associated ‘Candidatus Liberibacter asiaticus’ (Las) becomes strategic to warrant crop sustainability, but no resistant Citrus genotypes exist. Some Citrus relatives of the family Rutaceae, subfamily Aurantioideae, were described as full-resistant to Las, but they are phylogenetically far, thus incompatible with Citrus. Partial resistance was indicated for certain cross-compatible types. Moreover, other genotypes from subtribe Citrinae, sexually incompatible but graft-compatible with Citrus, may provide new rootstocks able to restrict bacterial titer in the canopy. Use of seedlings from monoembryonic species and inconsistencies in previous reports likely due to Las recalcitrance encouraged us to evaluate more accurately these Citrus relatives. We tested for Las resistance a diverse collection of graft-compatible Citrinae species using an aggressive and consistent challenge-inoculation and evaluation procedure. Most Citrinae species examined were either susceptible or partially resistant to Las. However, Eremocitrus glauca and Papua/New Guinea Microcitrus species as well as their hybrids and those with Citrus arose here for the first time as full-resistant, opening the way for using these underutilized genotypes as Las resistance sources in breeding programs or attempting using them directly as possible new Las-resistant Citrus rootstocks or interstocks.

Citriculture is an important agricultural activity worldwide, occupying a relevant position in Brazil among fruit tree production for both the fresh fruit market and the processing industry for concentrated orange juice export. Recent advances in the country’s citrus nursery tree production system have been essential to guarantee the efficiency and competitiveness of Brazilian citriculture. The implementation of strict laws and regulations to produce trees in protected environments and improvements in production techniques for basic citrus propagation materials and nursery trees in São Paulo state has excluded the insect vectors of destructive diseases such as citrus variegated chlorosis and huanglongbing, making this an innovative reference system for citrus propagation around the globe. The main aspects of these advances are presented and discussed in this review, including advances in propagation techniques, scion and rootstock selection, genetic characterization and certification, tree size standards, cultural practices such as irrigation and fertilization for the production of citrus propagation materials and nursery trees, and nursery management tools.

-In the State of Bahia, Brazil, the citrus industry is located on the north coast with the prevalence of the combination 'Pera' sweet orange on 'Rangpur' lime. Scion-rootstock diversification may contribute to the increase of yield and the extension of harvest season, as long as to decrease the risk associated to abiotic and biotic stresses. Therefore, the performance of 'Tuxpan Valencia' sweet orange grafted onto 14 rootstocks was evaluated in Rio Real -BA. Planting was performed in 2006 under rainfed cultivation on cohesive ultisol and tree spacing of 6.0 m x 4.0 m. Tree size, yield and fruit quality were evaluated in the period of

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The production system for certified citrus nursery trees in São Paulo State, Brazil, stipulates the use of screenhouses, rigorous selection of rootstocks, and the production of budwood under high standards in order to prevent diseases such as sudden death, Citrus Var, and foot rot (Phytophthora spp.). The establishment of adequate nutritional levels for citrus nursery trees also leads to higher production efficiency in this system. This work was divided into two trials. The first evaluated the influence of certain concentrations and formulas of slow-release fertilizer on the growth of 'Pera' sweet orange (Citrus sinensis L. Osbeck) budded on 'Rangpur' lime (Citrus limonia Osbeck) on two substrates. The development of 'Rangpur' lime liners was not influenced by composition of the substrate, nor by the concentrations or formulas of slow-release fertilizers. Substrate composition and formulas, or concentrations of fertilizers also did not affect budded tree growth, except that the greatest root fresh and dry matter were found in plants cultivated with lower concentrations. The second trial evaluated the influence of different soluble and slow-release fertilizers on growth of 'Valencia' sweet orange (Citrus sinensis L. Osbeck) nursery trees budded on 'Rangpur' lime. Scion length, stem diameter, scion fresh and dry matter, and leaf area were not affected by fertilizer sources. Fertigation induced the greatest development of roots (fresh and dry matter) when limestone was added.