Influência do genótipo e do estádio de maturação na colheita sobre a matéria fresca, qualidade e cura dos bulbos de cebola

Avaliou-se a influência do genótipo e do estádio de maturação da planta de cebola, na colheita, sobre o tamanho e qualidade, e subseqüente perda de matéria fresca na cura dos bulbos de 'Granex', 'Baia Periforme' e 'Jubileu'. A antecipação ou retardamento da colheita em 15 dias, em relação ao estalo da planta, não influenciou a matéria fresca total e o teor de açúcares solúveis totais dos bulbos, sendo estas características função do genótipo utilizado. A colheita antecipada dos bulbos em 15 dias reduziu significativamente o teor de sólidos solúveis na cultivar Baia Periforme. Os bulbos dos genótipos analisados apresentaram concentrações insignificantes de amido, inferiores a 0,16 % da matéria fresca. A média geral da concentração de açúcares solúveis totais foi de 6,8% da matéria fresca para o híbrido precoce 'Granex', 11,5% para a cultivar de ciclo médio Baia Periforme e 10,8% em bulbos da tardia 'Jubileu'. A colheita dos bulbos 15 dias após o tombamento do pseudocaule permitiu acúmulo significativo de compostos fenólicos solúveis na casca das cultivares Baia Periforme e Jubileu, de coloração amarelada. Durante a cura dos bulbos houve maior taxa de perda de matéria fresca naquelas plantas colhidas 15 dias antes do colapso do pseudocaule, independente do genótipo testado.The influence of cultivar and maturity stage at harvest over the weight, quality and weight loss through cure of onions was evaluated for cultivars Granex, Baia Periforme and Jubileu. Harvesting 15 days before the drop of tops did not affect the total bulb fresh weight or total soluble content, which were function of the genotype tested. Earlier harvesting, 15 days before maturation, significantly reduced the total soluble solids for 'Baia Periforme'. The bulbs presented small amount of starch, bellow 0.16% of the fresh weight. The general average for total soluble sugars was 6.8%; 11.5% and 10.8% of bulb's fresh weight, for the early hybrid 'Granex', the middle season cultivar Baia Periforme and late season cultivar Jubileu, respectively. Hharvesting bulbs in 15 days after the tops tall over, induced significant increase in the total soluble phenolic compounds in the skin of the bulb for 'Baia Periforme' and 'Jubileu', known as yellow dark skin cultivars. During the cure of the bulbs, harvesting 15 days before the top tall over, a higher rate of fresh weight loss was observed, irrespective of the genotype tested

Selection and validation of reference genes for quantitative gene expression analyses in various tissues and seeds at different developmental stages in Bixa orellana L.

Bixa orellana L., popularly known as annatto, produces several secondary metabolites of pharmaceutical and industrial interest, including bixin, whose molecular basis of biosynthesis remain to be determined. Gene expression analysis by quantitative real-time PCR (qPCR) is an important tool to advance such knowledge. However, correct interpretation of qPCR data requires the use of suitable reference genes in order to reduce experimental variations. In the present study, we have selected four different candidates for reference genes in B. orellana, coding for 40S ribosomal protein S9 (RPS9), histone H4 (H4), 60S ribosomal protein L38 (RPL38) and 18S ribosomal RNA (18SrRNA). Their expression stabilities in different tissues (e.g. flower buds, flowers, leaves and seeds at different developmental stages) were analyzed using five statistical tools (NormFinder, geNorm, BestKeeper, ΔCt method and RefFinder). The results indicated that RPL38 is the most stable gene in different tissues and stages of seed development and 18SrRNA is the most unstable among the analyzed genes. In order to validate the candidate reference genes, we have analyzed the relative expression of a target gene coding for carotenoid cleavage dioxygenase 1 (CCD1) using the stable RPL38 and the least stable gene, 18SrRNA, for normalization of the qPCR data. The results demonstrated significant differences in the interpretation of the CCD1 gene expression data, depending on the reference gene used, reinforcing the importance of the correct selection of reference genes for normalization