ABSTRACT.To obtain accurate and reliable results for the expression of genes of interest using quantitative real-time polymerase chain reaction (RT-qPCR) techniques, it is necessary to normalize the data by comparing them to constitutive genes that exhibit uniform expression levels under experimental conditions. In this study, the stability of expression was evaluated for the following ten candidate reference genes in rice leaves (Oryza sativa L.) from the BRS Bojuru and BRS Ligeirinho genotypes that were subjected to salt stress (150 mM): actin 11 (ACT11), beta-tubulin (β-TUB), eukaryote elongation factor 1-α (Eef-1), eukaryotic initiation factor 4-α (eIF-4-α), E2 ubiquitinconjugating enzyme (UBC-E2), ubiquitin 5 (UBQ5), ubiquitin 10 (UBQ10), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), TIP41-like, and cyclophilin. The stability of expression for the aforementioned genes was then compared to that of three LTP genes using UBQ10, Eef-1, and eIF-4-α as references. After analyzing the Reference genes for RT-qPCR in rice under salt stress expression levels using analysis of variance tests, the results indicated that UBQ10 was the most stable in all treatments (M = 0.404 and SV = 0.327). Furthermore, the eIF-4-α, TIP41-like, and cyclophilin genes exhibited the highest total coefficient of variation (CV = 269, 169.2, 179.2, respectively), which signifies that they exhibited the least stable expression. The expression levels of each candidate gene (LTP7, LTP10, and LTP13) were in contrast to the reference genes. Therefore, we concluded that UBQ10 is the best reference gene for RT-qPCR reactions under the experimental conditions. The expression analysis of LTP7, LTP10, and LTP13 confirmed the importance of validating reference genes to achieve accurate RT-qPCR results.

Resumo -O objetivo deste trabalho foi avaliar o efeito de diferentes porta-enxertos no desenvolvimento vegetativo, fenológico e produtivo do pessegueiro [Prunus persica (L.) Batsch] cv. Chimarrita. Os portaenxertos utilizados foram 'Capdeboscq', 'Tsukuba 1', 'Okinawa', 'Aldrighi' e 'GF 305'. As variáveis analisadas foram: diâmetro do tronco, volume da copa, material retirado da poda, época de brotação, época de fl oração, quantidade de clorofi la, área foliar específi ca, comprimento dos ramos principais, produtividade, massa dos frutos, coloração do fruto, fi rmeza de polpa, teor de sólidos solúveis totais (SST), acidez titulável (TA), relação SST/AT, fenóis totais e época de maturação. O delineamento experimental foi o de blocos ao acaso, com quatro repetições com cinco plantas cada. Não houve efeito dos porta-enxertos em: início da brotação, início da queda de folha, área foliar específi ca e maturação e massa de fruto. O diâmetro de tronco, comprimento de ramos, volume de copa, massa verde da poda e quantidade de clorofi la foram infl uenciados mais pelos porta-enxertos 'Capdeboscq', 'Okinawa' e 'Tsukuba 1'. O maior número de fl ores por ramo foi obtido com o porta-enxerto 'Capdeboscq'. Frutos mais avermelhados foram produzidos com o porta-enxerto 'GF 305', e os vermelhoamarelados com 'Okinawa'.Termos para indexação: Prunus, desenvolvimento, fenologia, fl oração, produtividade. Vegetative, phenological and productive characteristics of peach trees cultivar Chimarrita grafted on different rootstocksAbstract -The aim of this work was to evaluate the effect of different rootstocks on vegetative, phenological and productive development of peach trees [Prunus persica (L.) Batsch] cv. Chimarrita. The rootstocks used were 'Capdeboscq', 'Tsukuba 1', 'Okinawa', 'Aldrighi' and 'GF 305'. The variables studied were: trunk diameter, canopy volume, pruning weight, leafi ng and fl owering time, chlorophyll content, leaf specifi c area, length of scaffold branches, fruit weight and color, fruit fl esh fi rmness, total soluble solid (TSS) content, titratable acidity (TA), TSS/TA ratio, total phenols and fruit ripening time. The experiment was carried out using a randomized block design with four replicates, with fi ve plants each. No effect of the rootstocks was verifi ed on the beginning of leafi ng, and on leaf fall, leaf specifi c area, and fruit ripening and weight. The trunk diameter, length of branches, canopy volume, weight of the material removed by the pruning and chlorophyll content were better infl uenced by 'Capdeboscq', 'Okinawa' and 'Tsukuba 1'. The highest number of fl owers per branch was obtained with the rootstock 'Capdeboscq'. 'GF 305' provided redder fruits and 'Okinawa' redder-yellow fruits.

Many plant processes depend on differential gene expression, which is generally controlled by complex proteins called transcription factors (TFs). In peach, 1533 TFs have been identified, accounting for about 5.5% of the 27,852 protein-coding genes. These TFs are the reference for the rest of the Prunus species. TF studies in Prunus have been performed on the gene expression analysis of different agronomic traits, including control of the flowering process, fruit quality, and biotic and abiotic stress resistance. These studies, using quantitative RT-PCR, have mainly been performed in peach, and to a lesser extent in other species, including almond, apricot, black cherry, Fuji cherry, Japanese apricot, plum, and sour and sweet cherry. Other tools have also been used in TF studies, including cDNA-AFLP, LC-ESI-MS, RNA, and DNA blotting or mapping. More recently, new tools assayed include microarray and high-throughput DNA sequencing (DNA-Seq) and RNA sequencing (RNA-Seq). New functional genomics opportunities include genome resequencing and the well-known synteny among Prunus genomes and transcriptomes. These new functional studies should be applied in breeding programs in the development of molecular markers. With the genome sequences available, some strategies that have been used in model systems (such as SNP genotyping assays and genotyping-by-sequencing) may be applicable in the functional analysis of Prunus TFs as well. In addition, the knowledge of the gene functions and position in the peach reference genome of the TFs represents an additional advantage. These facts could greatly facilitate the isolation of genes via QTL (quantitative trait loci) map-based cloning in the different Prunus species, following the association of these TFs with the identified QTLs using the peach reference genome.

-The present study evaluated the germination potential of seeds from eight peach tree rootstocks under different stratification methods, aiming at the production of high quality seedlings. In the first experiment, seeds with endocarp from eight genotypes ('Aldrighi', 'Capdeboscq', 'Flordaguard', 'Okinawa', 'Okinawa roxo', 'Tsukuba 1', 'Tsukuba 2', 'Tsukuba 3') were stratified on sand and moist vermiculite, at 7 ºC for 60 days. In the second experiment, endocarpless seeds of the same genotypes were stratified on Petri dishes at 7 ºC. In the third experiment, the time at which at least 75% of the seedlings reached transplanting height (15 cm high) was verified. The endocarp was a limiting factor for seed germination of the eight rootstocks, since the highest germination percentages were 21% and 48.3% for 'Aldrighi' and 'Capdeboscq', respectively. Germination of 'Okinawa' was only 19.2% and 4.2%, in sand and vermiculite, respectively. Seeds stratified without the endocarp, showed 100% germination, except for 'Flordaguard' and 'Tsukuba 2' and 3', with 93% germination. Seed mass presented a positive correlation with the germination speed index and the initial growth of the seedlings. 'Aldrighi' and 'Capdeboscq' presented more vigorous seedlings with greater growth in height, stem diameter, and Dickson quality index.

ABSTRACT

-This study aimed at determining and correlating the main morphometric characteristics of fruits and seeds with the germination potential and vigor of eight peach rootstocks. The experimental design was completely randomized, with four replications of 50 seeds per treatment. The analyzed variables were: length, width, thickness, fresh mass of fruit and seeds, moisture content of seeds, percentage of seeds attacked by fungi and intact seeds, germination percentage, germination speed index (GSI) and mean germination time (MGT). The Capdeboscq, Aldrighi and Tsukuba 1 cultivars showed higher values of length, width, thickness and fresh mass of seeds compared to other cultivars, presenting a relationship with the later period of fruit ripening. Regardless of the fruit ripening time, the germination percentage was high, ranging between 93% and 100% for all cultivars. In addition, the fresh mass of fruits has showed a high positive correlation with the fresh mass of seeds for the eight evaluated peach rootstocks. The GSI and MGT have a high relationship with the fresh mass of seeds.Index terms: Rosaceae, morphobiometry, seeds, cultivars, peach.Correlação de características biométricas de frutos e sementes com a germinação e vigor de porta-enxertos de Prunus persica RESUMO -Objetivou-se determinar e correlacionar as principais características morfométricas de frutos e sementes sobre o potencial de germinação e o vigor de oito porta-enxertos de pessegueiro. O delineamento experimental foi inteiramente casualizado com quatro repetições de 50 sementes por tratamento. As variáveis analisadas foram: comprimento, largura, espessura, massa fresca dos frutos e sementes, grau de umidade de sementes, porcentagem de sementes intactas e infectadas por fungos, porcentagem de germinação, índice de velocidade de germinação (IVG) e tempo médio de germinação (TMG). As cultivares Capdeboscq, Aldrighi e Tsukuba 1 apresentaram maiores valores médios de comprimento, largura, espessura e massa fresca de sementes comparados com as demais cultivares, apresentando relação com o período mais tardio de maturação dos frutos. Independente da época de maturação dos frutos, a porcentagem de germinação foi alta variando entre 93% e 100% para todas as cultivares. Somado a isso, a massa fresca do fruto apresenta alta correlação positiva com a massa fresca das sementes dos oito porta-enxertos de pessegueiro avaliados. O IVG e o TMG possuem alta relação com a massa fresca das sementes.

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RESUMO -O trabalho teve por objetivo avaliar a resposta agronômica da cv. Chimarrita enxertada em cinco porta-enxertos, nas condições edafoclimáticas da região de Pelotas-RS, no período de 2003 a 2005. Durante o período de execução do experimento, foram avaliados o diâmetro do tronco do porta-enxerto e da cultivar-copa, comprimento médio dos ramos principais, volume de copa, massa fresca e massa seca do material vegetal retirado nas podas verde e de inverno, índice de intensidade de poda, massa média dos frutos, produção por planta, eficiência produtiva, produção por hectare, sólidos solúveis totais, firmeza da polpa, diâmetro e coloração dos frutos. O porta-enxerto 'Capdeboscq' induziu o maior crescimento vegetativo na cv. Chimarrita durante os três anos de avaliação, seguido do porta-enxerto 'Okinawa'. Este, por sua vez, induziu o maior rendimento produtivo (1,65 t ha -1 ). A cv. Capdeboscq proporcionou a obtenção de frutos com maior massa. Os porta-enxertos 'GF 305' e 'Aldrighi' induziram menor desenvolvimento vegetativo e a mais baixa produtividade (0,52 t.ha -1 ) . Termos para indexação: Prunus persica, produtividade, vigor e eficiência produtiva. AGRONOMICAL BEHAVIOR OF cv. CHIMARRITA ON FIVE ROOTSTOCKS OF PEACH TREESABSTRACT -The objective for this study was to evaluate the agronomical behavior of cv. Chimarrita on five rootstocks of peach trees in Pelotas-RS from 2003 to 2005. The variables evaluated were: trunk diameters of the rootstock and of the scion; length of the annual terminal growth; volume of the canopy; fresh and dry weight of the material taken by the summer and winter pruning; pruning intensity index; fruit weight; fruit production per tree; production efficiency; productivity per hectare; total soluble solids; pulp firmness; and fruit diameter and color. It was observed that the trees from: rootstock 'Capdeboscq' promoted higher vegetative growth and larger fruits, followed by the ones from the rootstock 'Okinawa' which promoted the highest yield (1, 65 t.ha -1 ); the rootstock 'GF 305' and 'Aldrighi' had the lowest vegetative development and yield (0, 52 t.ha -1 ).