Abstract
Several studies have been developed to understand the physiology of seed deterioration, however, the initial steps of the deterioration process are not completely clear. Seed vigor and viability losses are also associated with genetic material damage. This study was carried out to detect cytogenetic and physiological alterations occurring during the deterioration process of wheat seeds, due to artificial aging stress. Two cultivars, Ônix and Fundacep Campo Real, were submitted to six different treatments: control (T1), 24 (T2), 48 (T3), 72 (T4), 96 (T5) and 120 (T6) hours under artificial aging conditions: 42 °C and 100% relative humidity. Germination and vigor tests (First Count of Germination, Electrical Conductivity, Seedling Emergence in the Field and Emergence Speed Index) were performed. Cytogenetic evaluations were performed through smear technique for root tips, stained with 2% acetic orcein. Total number of cells under division and mitotic index (MI) were determined. According to results, vigor and mitotic index were affected due to deterioration process induced by artificial aging stress. A reduced number of dividing cells were observed in seeds submitted to prolonged period of aging. Chromosomal abnormalities in mitotic cells of aged seeds were detected with the occurrence of micronuclei, chromosome breaks and bridges.
Highlights
Wheat is the dominant crop in temperate areas, used for human food and livestock feed and it is the third three largest cereal crop, with over 600 million tonnes harvested annually in the world (Shewry, 2009)
Our results show that cell division and the mitotic index alters and these are sensitive indicatives of wheat seed deterioration
The use of artificial aging stress was an efficient method to study the changes occurring due to seed deterioration process, because physiological quality of seeds is negatively affected by accelerated aging stress time (Table 1)
Summary
Wheat is the dominant crop in temperate areas, used for human food and livestock feed and it is the third three largest cereal crop, with over 600 million tonnes harvested annually in the world (Shewry, 2009). Among the factors that affect wheat yield is the quality of seeds used, in respect to the germination and seedling establishment. Brazil grows more than 2 million hectares of wheat, which demands more than 200.000 tons of seeds (Abrasem, 2013). A sequence of events during seed deterioration which leads to loss of germination and field performance was proposed by Delouche and Baskin (1973). According to this model, degradation of membranes is the first event during seed deterioration process in which the loss of membrane permeability leads to increased leaching of seed cell constituents and electrolyte leakage affecting seed viability
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