Variation in the ribosomal DNA intergenic spacer of a maize population mass-selected for high grain yield

1990 ◽  
Vol 79 (6) ◽  
pp. 793-800 ◽  
Author(s):  
T. R. Rocheford ◽  
J. C. Osterman ◽  
C. O. Gardner
Genetics ◽  
1995 ◽  
Vol 141 (4) ◽  
pp. 1327-1337
Author(s):  
T J Crease

Abstract Nucleotide variation was surveyed in 21 subrepeat arrays from the ribosomal DNA intergenic spacer of three Daphnia pulex populations. Eighteen of these arrays contained four subrepeats. Contrary to expectations, each of the four positions within the array had a different consensus sequence. However, gene conversion, involving sequences less than the length of a subrepeat, had occurred between subrepeats in different positions. Three arrays had more than four subrepeats and were undoubtedly generated by unequal crossing over between standard-length arrays. The data strongly suggested that most unequal exchanges between arrays are intrachromosomal and that they occur much less frequently than unequal exchanges at the level of the entire rDNA repeat. Strong associations among variants at different positions allowed the recognition of five groups of arrays, two of which were found in more than one population. Five of the seven individuals surveyed had arrays from more than one group. Analysis of the distribution of nucleotide variation suggested that the populations were quite divergent, a result that is concordant with previous surveys of allozyme and mitochondrial DNA variation. It was suggested that some of the subrepeat array types are quite old, at least predating the recolonization of pond habitats in the midwestern United States after the last glaciation.


Genome ◽  
1994 ◽  
Vol 37 (4) ◽  
pp. 664-671 ◽  
Author(s):  
Lang Zhuo ◽  
S. L. Sajdak ◽  
R. B. Phillips

Intraspecific variation in the sequence of the transcribed spacer regions of the ribosomal DNA (rDNA) in lake trout was examined by restriction mapping and sequencing of these regions amplified by the polymerase chain reaction. The length of the first internal transcribed spacer region (ITS-1) was 566 bases and the second internal transcribed spacer region (ITS-2) was 368 bases in lake trout. When the 1.4-kb region including the ITS-1, the 5.8S coding region, and the ITS-2 was amplified from 12 individuals from four populations and digested with eight different enzymes only one intraindividual polymorphism was found that occurred in each population. When the amplified ITS-1 region was sequenced from an additional 10 individuals from five populations, no interindividual variation was found in the sequence. A 6-kb portion of the rDNA repeat unit including 1.6 kb of the 18S coding region, the 5′ external spacer region (5′ ETS), and part of the adjacent intergenic spacer was cloned and a restriction map was prepared for these regions in lake trout. No intraspecific variation was found in the region adjacent to the 18S rDNA, which includes the 5′ ETS, although intraspecific and intraindividual length variation was found in the intergenic spacer region 3–6 kb from the 18S. Sequencing of a 609-b segment of the 5′ ETS adjacent to the 18S coding region revealed the presence of two 41-b repeats. The 198-b sequence between the repeats had some similarity to the 18S coding region of other fishes. Primers were designed for amplification of 559 b of the 5′ ETS using the polymerase chain reaction. No intraspecific variation in this region in lake trout was found when the DNA amplified from this region in 12 individuals from four populations was digested with eight restriction enzymes.Key words: ribosomal DNA, internal transcribed spacer regions, 5′ external spacer region, transcribed spacer, lake trout.


1998 ◽  
Vol 28 (1) ◽  
pp. 11-19 ◽  
Author(s):  
K. Terashima ◽  
J. Y. Cha ◽  
T. Yajima ◽  
T. Igarashi ◽  
K. Miura

2017 ◽  
Vol 16 (3) ◽  
pp. 401
Author(s):  
CÁSSIO VITORAZZI ◽  
ANTONIO TEIXEIRA AMARAL JÚNIOR ◽  
LILIAM SILVIA CANDIDO ◽  
ISMAEL LOURENÇO DE JESUS FREITAS ◽  
THIAGO RODRIGUES DA CONCEIÇÃO SILVA

 RESUMO - A adequação do arranjo populacional está entre as técnicas que podem maximizar a produtividade da cultura do milho. Daí a importância das pesquisas que buscam estudar o desempenho de cultivares de milho e milhos especiais, a fim de determinar o arranjo de plantas ideal. O objetivo deste trabalho foi avaliar o desempenho da variedade UENF-14, de milho pipoca, cultivada em diferentes arranjos populacionais, na safra e safrinha, para otimizar a recomendação fitotécnica para os produtores rurais do Norte Fluminense. Foram instalados dois experimentos em Campos dos Goytacazes-RJ. Um na safrinha 2011 utilizando a variedade UENF-14 e o híbrido experimental P2 x P9, e o outro na safra 2011-2012, com a variedade UENF-14 e o híbrido comercial IAC-112. O delineamento experimental, nos dois experimentos, foi o de blocos casualizados arranjados em parcelas subsubdivididas, em que as parcelas foram compostas pelos genótipos, as subparcelas constituídas pelos espaçamentos entre linhas de semeadura (0,45, 0,60 e 0,90 m) e as subsubparcelas compostas pelas densidades de plantas (60.000, 75.000 e 90.000 plantas ha-1). A UENF-14 apresentou desempenho superior aos híbridos, demonstrando seu potencial para cultivo na região Norte Fluminense. Houve aumento do rendimento de grãos com a diminuição do espaçamento entre linhas de plantio. Para a variedade UENF-14, a redução do espaçamento entre linhas de plantio foi vantajosa para a produção de grãos, independentemente da época de semeadura.Palavras-chave: Zea mays L., densidade de semeadura, espaçamento entre linhas, épocas de semeadura.  POPULATION ARRANGEMENT FOR THE VARIETY OF POPCORN UENF-14 ABSTRACT - The adequacy of the maize population arrangement is among the most important techniques for obtaining higher yields. Therefore, many researchers have been conducting an attempt to study the performance of corn and specialty corn. The objective was to evaluate the performance of the popcorn variety UENF-14 in different population arrangements, in the harvest season and off-season. Two experiments were carried out in Campos dos Goytacazes, North of Rio de Janeiro State, Brazil, in the off-season 2011, using the UENF-14 variety and the experimental hybrid P2 x P9, and in the season 2011-2012 using UENF-14 and the commercial hybrid IAC-112. The treatments were arranged in randomized complete block design with split plots, in which plots were composed by popcorn genotypes, the subplots consisting of three spacings between sowing lines (0.45, 0.60 and 0.90 m) and the subsubplots composed of three plants per hectare densities (60,000, 75,000 and 90,000 plants.ha-1). The variety UENF-14 presented higher performance than the hybrids, demonstrating its potential for recommendation to the North of Rio de Janeiro State. There was an increase of grain yield by reducing the spacing between the plants rows. The cultivation of the variety UENF-14 reducing the spacing between rows was advantageous for grain production, regardless of planting date.Keywords: Zea mays L., densities of plants, spacing between rows, sowing times.


2002 ◽  
Vol 157 (1) ◽  
pp. 69-74 ◽  
Author(s):  
Pasquapina Ciarmela ◽  
Lucia Potenza ◽  
Luigi Cucchiarini ◽  
Sabrina Zeppa ◽  
Vilberto Stocchi

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