RESUMO
Genome wide selection (GWS) is essential for the genetic improvement of perennial species such as Citrus because of its ability to increase gain per unit time and to enable the efficient selection of characteristics with low heritability. This study assessed GWS efficiency in a population of Citrus and compared it with selection based on phenotypic data. A total of 180 individual trees from a cross between Pera sweet orange (Citrus sinensis Osbeck) and Murcott tangor (Citrus sinensis Osbeck x Citrus reticulata Blanco) were evaluated for 10 characteristics related to fruit quality. The hybrids were genotyped using 5287 DArT_seqTM (diversity arrays technology) molecular markers and their effects on phenotypes were predicted using the random regression - best linear unbiased predictor (rr-BLUP) method. The predictive ability, prediction bias, and accuracy of GWS were estimated to verify its effectiveness for phenotype prediction. The proportion of genetic variance explained by the markers was also computed. The heritability of the traits, as determined by markers, was 16-28%. The predictive ability of these markers ranged from 0.53 to 0.64, and the regression coefficients between predicted and observed phenotypes were close to unity. Over 35% of the genetic variance was accounted for by the markers. Accuracy estimates with GWS were lower than those obtained by phenotypic analysis; however, GWS was superior in terms of genetic gain per unit time. Thus, GWS may be useful for Citrus breeding as it can predict phenotypes early and accurately, and reduce the length of the selection cycle. This study demonstrates the feasibility of genomic selection in Citrus.
Assuntos
Cruzamento , Citrus/genética , Genoma de Planta , Seleção Genética , Marcadores Genéticos , Variação Genética , Padrões de Herança/genética , Fenótipo , Característica Quantitativa HerdávelRESUMO
Brevipalpus phoenicis s.l. is an economically important vector of the Citrus leprosis virus-C (CiLV-C), one of the most severe diseases attacking citrus orchards worldwide. Effective control strategies for this mite should be designed based on basic information including its population structure, and particularly the factors that influence its dynamics. We sampled sweet orange orchards extensively in eight locations in Brazil and 12 in Mexico. Population genetic structure and genetic variation between both countries, among locations and among sampling sites within locations were evaluated by analysing nucleotide sequence data from fragments of the mitochondrial cytochrome oxidase subunit I (COI). In both countries, B. yothersi was the most common species and was found in almost all locations. Individuals from B. papayensis were found in two locations in Brazil. Brevipalpus yothersi populations collected in Brazil were more genetically diverse (14 haplotypes) than Mexican populations (four haplotypes). Although geographical origin had a low but significant effect (ca. 25%) on the population structure, the greatest effect was from the within location comparison (37.02 %). Potential factors driving our results were discussed.
Assuntos
Citrus/virologia , Variação Genética , Insetos Vetores/genética , Ácaros/genética , Doenças das Plantas/virologia , Animais , Brasil , Haplótipos , México , Ácaros/virologiaRESUMO
There are two bacilliform, rhabdo-like viruses that cause citrus leprosis: Citrus leprosis virus C (CiLV-C), which accumulates in the cytoplasm of infected cells, and Citrus leprosis virus nuclear type (CiLV-N), which accumulates in their nucleus. The first one, the prototype of the new genus Cilevirus, is prevalent and occurs in several countries of the American continent, from Argentina to Mexico (1). The second type, still a tentative member of the Rhabdoviridae family, is of rare occurrence, with a few reports in Brazil and one in Panama (1). Leprosis is particularly important to the Brazilian citrus industry because of the 60 to 80 million dollars spent yearly for the control of Brevipalpus phoenicis (Geijskes, 1939) (Acari: Tenuipalpidae), the vector of the virus (1). For decades, the disease was considered unique to citrus plants; however, greenhouse experiments conducted in the 1990s demonstrated the mechanical transmission of CiLV-C to noncitrus plants (1). Years later, researchers were able to transmit the virus to nonrutaceous hosts using viruliferous mites (1,4). Recently, León et al. (2) reported the occurrence of the first noncitrus plant naturally infected by CiLV-C, the rutaceous Swinglea glutinosa Blanco (Merr.). Tropical spiderworts (Commelina benghalensis L.; Commelinaceae) are monocot weeds commonly found in citrus orchards in Brazil. In a survey conducted in orchards with high incidences of leprosis in the municipalities of Borborema and São José do Rio Preto, State of Sao Paulo, Brazil, tropical spiderworts were found exhibiting necrotic spots with a yellow halo in green leaves and green spots with necrotic center in senescent leaves. Since these symptoms are similar to those caused by CiLV-C in citrus, symptomatic plants were collected and subjected to transmission electron microscopy analyses and reverse transcription-PCR using primers that specifically amplify a region within the putative movement protein gene of the virus (3). Bacilliform virus particles and typical inclusions were seen in the lesions. Bands of the expected 344 bp size were seen in agarose gels of symptomatic samples only. The analysis of the consensus sequence showed 100% identity with CiLV-C sequence available in the GenBank (Accession No. YP_654542.1). Experimental transmission of CiLV-C by B. phoenicis reproduced the lesions in inoculated tropical spiderwort. Also, the virus could be easily transmitted back from C. benghalensis to sweet orange plants. Our data show that this widespread weed is the first monocot as a natural host for CiLV-C. Since tropical spiderwort is a host for B. phoenicis and symptomatic plants were found in two municipalities 130 km apart from each other, it is possible that this weed may serve as reservoir for the virus and play a relevant role in the spread of the disease in the field, but this issue still needs to be addressed in further experiments. References: (1) M. A. Bastianel et al. Plant Dis. 94:284, 2010. (2) M. G. A. Leon et al. Plant Dis. 90:682, 2008. (3) E. C. Locali-Fabris et al. Plant Dis. 87:1317. (4) M. A. Nunes et al. Plant Dis. Online publication. doi:10.1094/PDIS-06-11-0538, 2011.
RESUMO
The diagnosis of plant diseases caused by Brevipalpus-transmitted viruses (BrTVs) has been done through the analyses of symptoms, transmission electron microscopy, and RT-PCR of infected plant tissues. Here, we report the detection of Citrus leprosis virus C, Orchid fleck virus, Clerodendrum chlorotic spot virus and Solanum violaefolium ringspot virus in their viruliferous vectors Brevipalpus spp. using specific primer pairs for each of the viruses. The efficiency of virus transmission by Brevipalpus mites is low, so the detection of these pathogens in their vectors could constitute an important tool for studies involving virus-vector relationships, transmission, and monitoring the pathogen prior to the appearance of symptoms in the field.
Assuntos
Vetores Aracnídeos/virologia , Ácaros/virologia , Doenças das Plantas/virologia , Rhabdoviridae/isolamento & purificação , Animais , Primers do DNA , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Rhabdoviridae/genéticaRESUMO
Two patients who were initially given a diagnosis of Langerhans' cell histiocytosis on the basis of the clinical, radiologic, and biopsy findings had mycobacterial infection subsequently identified. The correct diagnosis of dominant partial interferon-gamma receptor deficiency was established.