Inheritance was studied in natural variants of the soybean cultivar Parana, developed under photoperiodic conditions ranging from 13 h 31 min day light, at sowing, to 14 h 23 min, 59 days afterwards. Results indicated that early flowering and maturity are controlled by a single dominant gene. Natural mutations that originated cultivars Paranagoiana and SS-1 occurred at the same locus of cultivar Parana. It was not possible to determine if the recessive alleles of these mutant cultivars are different. The designation E6 was proposed for the alleles determining earliness in cultivar Parana, and e6 for the gene determining late flowering and maturity in cultivars Paranagoiana and SS-1, until the individuality of the alleles of Paranagoiana and SS-1 is confirmed.

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E6, a dominant gene conditioning early flowering and maturity in soybeans

Soybean (Glycine max (L.) Merrill)is a short day plant that flowers when days are shorter than the maximum critical value, and this period is specific for each genotype. Soybean sensitivity to photoperiodism determines the limits of the sowing period for a latitude and hinders adaptation to wider ranges of latitude. The long juvenile period (LJP), which delays flowering under short day condictions, has been identified in soybean cultivars. The introduction of the LJP characteristic in soybean has made its cultivation possible in regions with latitudes lower than 15 o . Knowledge of the controlling genetic mechanisms of this characteristic can help in the development of soybean genotypes for lower latitudes with greater adaptation to sowing periods within the same latitude. Some conclusions about the genetic LJP control in soybean were reached from the present review: a) plants with LJP have a lower development rate for flowering, resulting in the lengthening of the vegetative period; b) the LJP characteristic has a direct influence on plant photoreceptivity and flowering induction; c) the genetic control of flowering time in short days is determined by a different and independent genetic system from that which determines long day flowering time; d) late flowering under short day conditions is a quantitative characteristic controlled by recessive genes, and it is believed that one to five main genes control flowering. Genotypes with a single pair of recessive alleles did not have LJP.

Photoperiodism and Genetic Control of the Long Juvenile Period in Soybean: A Review

The objectives of this research were: a) evaluate heterosis for agronomic traits; b) identify associations among the traits; c) estimate genetic divergence among parents and verify its predictive value of hybrid performance. A 10 x 10 diallel experiment was carried out at two localities. Number of days to flowering (NDF), plant height at flowering (APF), number of days to maturity (NDM), plant height at maturity (APM), oil content (%OL), one-hundred seed weight (PCS), agronomic value (VA) and seed yield (PG) were evaluated. Genotype x locality interaction influenced the analysis; varieties and heterosis effects were significant for most traits. Positive values of heterosis were found for most traits, especially PG. Heterosis for NDF was for earliness. %OL showed to be controlled essentially by additive genes. VA can be used for indirect selection for PG. Parental mean predicted hybrid performance better than Mahalanobis’ distance (D 2 ); however, for some traits, this predicting ability was not sufficiently accurate.

Performance of agronomic traits in a soybean F 1 diallel system

Estimaram-se a herdabilidade e as correlacoes fenotipicas para alguns caracteres, em quatro populacoes F 2 , em soja. Estas populacoes foram oriundas dos cruzamentos entre as variedades ‘Parana'. ‘Sao Luiz', 'Vicoja' e 'Hardee' e seus respectivos mutantes de floracao e de maturacao tardia, Paranagoiana, PR 77-1000l, UFV-1 e IAC74-2736-10, As estimativas de herdabilidade para a estatura da planta na floracao, para os quatro cruzamentos, foram coerentemente maiores que as obtidas na maturacao, mostrando que para o mesmo carater ocorrem fases, no desenvolvimento da soja, em que a aplicacao de selecao deve ser mais eficaz. Para o cruzamento Parana x Paranagoiana, foi obtida correlacao positiva entre os caracteres ponto de insercao da primeira folha" e ponto do primeiro legume", evidenciando a existencia de uma relacao no x folha x legume para algumas variedades. Esta relacao implica que o ponto de insercao do primeiro legume na planta depende diretamente do ponto de insercao da primeira folha.

J. L. Gilioli

Papers

Heranca do numero de dias para floracao e maturacao em quatro mutantes naturais em soja (Glycine max (L.) Merrill)