Resumo No Programa de Melhoramento de Citros do Centro de Citricultura do Instituto Agronômico (IAC), foi desenvolvida uma cultivar, a tangerina IAC 2019Maria, proveniente do cruzamento entre tangor Murcott IAC (Citrus reticulata x Citrus sinensis) e laranja Pera IAC (C. sinensis). O presente trabalho teve como objetivo avaliar o número de sementes em frutos da tangerina IAC 2019Maria e identificar embriões zigóticos e plantas triploides dos cruzamentos entre tangerina IAC 2019Maria e laranja Pera IAC e tangerina Ponkan (C. reticulata Blanco), tangerina IAC 2019Maria em polinização aberta e de autopolinização. As flores de IAC 2019Maria foram autopolinizadas, polinizadas com pólens de laranja Pera e tangerina Ponkan e sem polinização. Os embriões foram identificados utilizando marcadores moleculares microssatélites e a ploidia foi avaliada por citometria de fluxo. Os resultados do tratamento sem polinização sugerem que a variedade não produz frutos partenocárpicos. Os resultados da genotipagem demonstraram que 100% de todas as populações consistem em embriões zigóticos, sugerindo que a tangerina IAC 2019Maria é uma planta com baixa taxa de poliembrionia. A análise da ploidia dos híbridos permitiu identificar uma planta triploide de semente abortada do cruzamento com laranja Pera e duas tetraploides, uma do cruzamento com laranja Pera e uma de autopolinização.

Abstract The Citrus Breeding Program of the Citriculture Center at the Agronomic Institute (IAC) has developed a mandarin cultivar IAC 2019Maria from the crossing between Murcott IAC tangor (Citrus reticulata x Citrus sinensis) and Pera IAC sweet orange (C. sinensis). The present study aimed to assess the number of seeds in fruits of IAC 2019Maria mandarin and to identify zygotic embryos and triploid plants in the crossings between IAC 2019Maria mandarin, Pera IAC sweet orange, and Ponkan mandarin (C. reticulata Blanco), in addition to IAC 2019Maria mandarin in open and self-pollination. IAC 2019Maria flowers were self-pollinated, pollinated with pollen from Pera sweet orange and Ponkan mandarin, and had no pollination. The embryos were identified using microsatellite molecular markers and ploidy was assessed by flow cytometry. The results of the treatment with no pollination suggest the variety does not produce parthenocarpic fruits. The genotyping results showed that 100% of the populations consist of zygotic embryos, suggesting that IAC 2019Maria mandarin is a plant with low polyembryony. The ploidy analysis of the hybrids allowed identifying a triploid plant from an aborted seed from the crossing with Pera sweet orange and two tetraploids, one from the crossing with Pera sweet orange and one from self-pollination.

Abstract Citrus plants have been extremely affected by Huanglongbing (HLB) worldwide, causing economic losses. HLB disease causes disorders in citrus plants, leading to callose deposition in the phloem vessel sieve plates. Callose is synthesized by callose synthases, which are encoded by 12 genes (calS1– calS12)in Arabidopsis thaliana. We evaluated the expression of eight callose synthase genes from Citrus in hybrids between Citrus sunki and Poncirus trifoliata infected with HLB. The objective of this work was to identify possible tolerance loci combining the expression quantitative trait loci (eQTL) of different callose synthases and genetic Single-Nucleotide Polymorphism (SNP) maps of C. sunki and P. trifoliata. The expression data from all CscalS ranged widely among the hybrids. Furthermore, the data allowed the detection of 18 eQTL in the C. sunki map and 34 eQTL in the P. trifoliata map. In both maps, some eQTL for different CscalS were overlapped; thus, a single region could be associated with the regulation of more than one CscalS. The regions identified in this work can be interesting targets for future studies of Citrus breeding programs to manipulate callose synthesis during HLB infection.