Relações entre medidas de qualidade de lotes de sementes de arroz

Abstract

RESUMO -A qualidade de um lote de sementes não é uma grandeza mensurável diretamente. É preciso a realização de diversos testes, cujos resultados conjuntamente permitem concluir quanto à sua qualidade. Dessa forma, pode haver a realização de testes redundantes, altamente relacionados entre si, sem que acrescente em poder de discriminação dos lotes e levando a desperdício de tempo e recursos para obtenção de uma recomendação. O objetivo desta pesquisa é identificar o conjunto de testes não correlacionados entre si para avaliar a qualidade de lotes de sementes de arroz. Assim, submeteu-se 67 lotes de sementes de arroz de diferentes procedências a nove testes para avaliação da sua qualidade fisiológica, incluindo variáveis morfológicas, de vigor e germinação. Estimou-se a matriz de correlação entre as nove variáveis e aplicou-se a análise fatorial, optando-se pelo número de fatores cuja variância acumulada fosse superior a 70%. Observou-se que a utilização de três fatores foi suficiente para acumular 80,4% da variância total e concluiu-se que a massa verde das plântulas, a percentagem de germinação e o comprimento da parte aérea, avaliadas aos 14 dias após a semeadura ou apenas o índice de velocidade de germinação e emergência no solo são suficientes para a identificação da qualidade dos lotes de sementes de arroz. Palavras-chave:Oryza sativa. Germinação. Redução variável. Semeadura.ABSTRACT -The quality of a seed batch is not a directly measurable quantity. It is necessary to carry out several tests, whose results together allow a conclusion as to quality. Thus, when attempting to arrive at a conclusion, tests may be carried out which are redundant and highly correlated, without adding to the ability to discriminate between batches, and leading to both wasted time and resources. The aim of this research is to identify a non-correlated set of tests to assess the quality of rice seed batches. Therefore 67 batches of rice seeds of different origins were submitted to nine different tests to assess physiological quality, including morphological variables, and those of vigor and germination. The correlation matrix among the nine variables was estimated and factor analysis applied, opting for the number of factors whose cumulative variance was greater than 70%. It was observed that using three factors was sufficient to reach 80.4% of the total variance, and concluded that the green mass of the plantlets, the percentage of germination and length of the shoots, all measured at 14 days after sowing, or simply the index of germination and emergence in the soil, are sufficient for identifying the quality of rice seed batches.

Discrimination of forage pea seed lots by means of multivariate techniques

“…Similarly, studies on vigor tests for soybean seeds (Barbosa et al, 2013) and piatã grass (Silva et al, 2017) also found that two principal components were sufficient to explain, respectively, 65.86 and 74.23% of the variance in the discrimination of variables. In contrast, in similar work with rice, Lorentz & Nunes (2013) verified the need for three principal components, which explained 80.42% of the characteristics.…”

“…For each of the principal components, all correlation values equal to or greater than 0.6 were considered relevant and with discriminatory power (Lorentz & Nunes, 2013;Silva et al, 2017). Thus, among the variables, only thousand seed weight had no discriminatory power in the two principal components.…”

“…The germination test is routinely used by the seed industry to determine physiological quality, and the results of vigor analyses are used to identify differences in the physiological quality of the lots, especially those with a similar percentage of normal seedlings (Brasil, 2009). Such analyses, performed in seed analysis laboratories, result in several partial information that aim to evaluate the physiological quality of the lots (Lorentz & Nunes, 2013). This information can help in the internal decision making of seed producing companies as to the destination of a given lot (Marcos Filho, 2015).…”

“…This is because they are highly related to other characteristics. Low discriminatory capacity highlights the identification and elimination of variables that do not present additional information to the user (Lorentz & Nunes, 2013), which can be done through multivariate analysis. This analysis represents a set of exploratory techniques that allows to discriminate seed lots with common characteristics, and aims at the minimum numbers needed to describe relevant information contained in the original observations (Barbosa et al, 2013).…”

Evaluation of vigor and tolerance of sweet corn seeds under hypoxia

“…The physiological quality of a seed lot is not easily measureable since only one individual evaluation is not sufficient to define the vigor of the lot. This property is defined by a set of tests; however, discrimination of lots in regard to vigor by means of combined observation of the data of all the tests is complex and time-consuming (Lorentz and Nunes, 2013).…”