Poliembrionia e atributos morfológicos de sementes de porta-enxertos de citros

Abstract

RESUMO -A poliembrionia é um caráter fundamental no melhoramento genético e na multiplicação comercial de porta-enxertos de citros. Este trabalho avaliou as relações entre poliembrionia e diferentes atributos morfológicos de sementes de 12 genótipos de citros selecionados como porta-enxertos. Foram analisadas 50 sementes por genótipo, quanto a massa, altura, largura, número de embriões, taxa de poliembrionia, grau de dificuldade de extração da testa, coloração da semente, estimada por um matiz das duas notas de cores predominantes, e razão de cor, calculada pela divisão entre a menor e a maior nota do matiz. Os resultados foram submetidos à análise de variância, comparando-se as médias pelo teste de Scott-Knott e determinando-se os coeficientes de correlação de Pearson entre as variáveis (P ≤ 0,05). Os porta-enxertos apresentaram atributos de sementes distintos, podendo ser agrupados em três classes de poliembrionia, destacando-se três seleções de limoeiro 'Cravo' com poliembrionia inferior a 50%, citrandarins como totalmente poliembriônicos e outros híbridos de Poncirus trifoliata com taxas baixas a intermediárias. O grau de dificuldade de extração da testa foi maior nas sementes menores. Na maioria dos genótipos avaliados, o número de embriões por semente correlacionou-se positivamente à massa, altura e largura de sementes e negativamente à razão de cor, sugerindo que a análise de coloração de sementes inteiras pode ser ferramenta alternativa para uma avaliação visual rápida da ocorrência de poliembrionia. Termos para indexação: Citrus spp., análise de cor da semente, melhoramento genético, morfologia da semente, poliembrionia, propagação.ABSTRACT -Seed polyembryony is an important trait for breeding and commercial multiplication of citrus rootstocks. This study evaluated relationships of polyembryony with different morphological seed traits of 12 citrus genotypes selected as rootstocks. The following traits were evaluated individually on 50 seeds per genotype: seed mass, height, width and embryo number, polyembryony level, difficulty for seed coat extraction, and seed color, which was estimated by a two-grade scale representing predominant colors on the endosperm. Data was submitted to variance analyses and the means were compared by the Scott-Knott Test (P ≤ 0.05). Pearson's Correlation Coefficients were determined among all variables for all genotypes and individually. Citrus rootstocks had significantly distinct seed traits and could be classified in three polyembryony groups, with three Rangpur lime selections presenting polyembryony lower than 50% and the citrandarins as totally polyembryonic. Other trifoliate hybrids showed low to intermediate polyembryony.Seed coat extraction was more difficult in smaller seeds. For majority of genotypes, the number of embryos in the seed had positive correlation to the seed mass, height and width and negative correlation to the color ratio, which was calculated by the division of the lowest and highest color grades. This result suggests that the whole seed color analys...

Determination of the best culture medium for establishment, propagation and conservation in vitro of citrus rootstocks

“…This was the case of the 'Indio' citrandarin, which stood out in MS and WPM (5.25 and 5.72,respectively), and for the hybrid TSKC x (LCR x TR) -059, whose mean value in WPM (3.19) was statistically superior to those obtained in the other two media (Table 2). However, in general the average number of plantlets produced in the three media (1.10 to 5.72, Table 2) was near the average number of embryos per seed, as observed for some of the same genotypes by DUARTE et al (2013) (1.88 to 6.02), making it possible to obtain a high number of germinated embryos per seed.…”

Morphology of seeds and seedlings, and substrates in germination of Citrus limetta

“…it was possible to observe the difference in coloration of cotyledons in the polyembryonic seed that originated four seedlings, two with cotyledons more greenish and the others tending to cream color. Regarding coloration, DUARTE et al (2013) affirmed that this characteristic of seeds is the result of color combination of cotyledons, it could vary according to the quantity of embryos in the seed, representing a possible estimate of the degree of polyembryony and for the identification of the zygotic embryo.…”

“…Polyembryony is an advantage for production of rootstocks, since that higher the rate, greater the chances of obtaining clones of the parent plant, which is the objective in the commercial multiplication of rootstocks. The lower production of clones, that is, only one seedling per seed, in genetical enhancement programs, could be used as female parents in controlled hybridizations and would be advantageous, allowing greater ease in obtaining and selecting the zygotic embryos of interest (DUARTE et al, 2013). KASHyAP et al (2018) affirmed that polyembryony varies according to the ecological region and the cultivar, suggesting that it is specific to each variety in relation to the region.…”

Embryo and Endosperm Phytochemicals from Polyembryonic Maize Kernels and Their Relationship with Seed Germination

“…One of the phenotypic traits that can increase production and nutritional quality of this commodity is polyembryony [4], since plants with this trait have a prolific seed, which may generate multiple plants per seed [5], promoting the emission of two to four radicles, and these can come out separately or together [6]. Polyembryony is classified as single or multiple depending on the number of individuals generated during development [7]. Furthermore, for genotypes with this trait, the number of seeds necessary to cover one surface area unit can be reduced [4], which may reduce cropping costs.…”