Abstract
Over 40% of the agricultural area in Brazil corresponds to no-tillage farming. Although it is evident the importance of obtaining upland rice cultivars adapted to this cropping system, researches in this sense are still incipient and breeders do not have cultivars available to recommend with enough security. The aim of this study was to evaluate phenotypic characters favorable to the no-tillage system in order to establish the basis for upland rice breeding programs interested in this cropping system. The seeds of twenty elite inbred lines from the Upland Rice Breeding Program from the Brazilian research institutions UFLA, EMBRAPA and EPAMIG were evaluated at the Central Seeds Lab from the Agriculture Department of UFLA following a randomized block design with four replicates. The characters evaluated were seedlings emergence (SE), green matter yield (GM), dry matter yield (DM), photosynthetic activity (PA), and superoxide dismutase activity (SOD). The quality parameters evaluated were obtained by a germination test (GT), germination first count (GFC), emergence test (E), initial stand (IS), and alpha-amylase expression. The lines CMG 2074, CMG 1967, CMG 2017, BRSMG Caravera and CMG 2097 showed higher SOD content in the enzymatic analyses, and consequently higher tolerance to abiotic stresses that could be caused by no-tillage. Considering the evaluation of agronomic traits, the line CMG 1967 showed the best performance in no-tillage soil and, therefore, should receive higher attention in Upland Rice Breeding Programs.
Highlights
Rice (Oryza sativa L.) is among of the most consumed cereals in the world, and is the main source of carbohydrates in Brazil [1]
The characters evaluated were: 1) Seedling emergence, as the number of days from sowing and the emergence of 50% of the plants from each plot; 2) Green matter yield, as the weight of green matter of one plant from each plot; 3) Dry matter yield, as the weight of the same sample used to determinate the green matter stored in warm house for 72 h in 65 ̊C and 0% of humidity; 4) Photosynthetic activity, as therelative chlorophyll index (RCI) measured by a chlorophyll meter (SPAD), obtained as the mean of 30 reedsin five leaves; 5) Superoxide dismutase (SOD) activity, obtained by spectrophotometry
They were centrifuged in 14.000 rpm for 30 minutes in 4OC degrees, and 60 μL of the sample were added to a polyacrylamide gel (7.5% of separator gel and 4.5% of concentrator gel) to perform electrophoretic analysis (150 Volts for 5 hours) using the gel/electrode system Tris-glycine pH 8.9
Summary
Rice (Oryza sativa L.) is among of the most consumed cereals in the world, and is the main source of carbohydrates in Brazil [1]. Brazilian production is mainly of irrigated rice, Brazil has the biggest cultivated area of upland rice in the world, mostly in the states of Mato Grosso, Tocantins and Maranhão [2] In these regions, rice is cultivated by small farmers without any irrigation, in acid soil, poor of nutrients, low water retention and with irregular rain precipitation [3]. Since the 80s, much of the upland rice has been cultivated in order to start new farmable fields in degraded pastures and deforested areas [2] This strategy has increased the cultivated area, the cultivation of upland rice should not be considered only in this situation, because it does not supply internal demand. The obtaining of upland rice cultivars adapted to no-tillage system enables rotation with other crops, supplies the rice demand and guarantees another alternative for small farmers
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