Seed wintering and deterioration characteristics between weedy and cultivated rice.

Jung-Sun Baek,Nam-Jin Chung

doi:10.1186/1939-8433-5-21

Abstract

BackgroundIncidences of weedy rice continuously occurred in paddy fields because its shattering seeds were able to over-winter. In this research, the seed deterioration of weedy rice was investigated compared with cultivated rice, and the wintering characteristics of these two types of rice were investigated with the field wintering test, freezing resistance test, and accelerated aging test.ResultsFor the wintering test, the seeds of weedy rice were placed on the soil surface of a paddy with cultivated rice seeds during the 2008/2009 and 2009/2010 winter seasons from November to April. The viability of seeds after wintering was 4.3% for cultivated rice, but 92.7% for weedy rice in 2008/2009. In the second wintering test, the seeds were placed under flooded and dry paddy conditions. The seed viability of cultivated rice was 5% in dry paddy and 0.5% in flooded paddy, but weedy rice maintained a high viability during winter of 90% in the dry paddy and 61% in the flooded paddy. Following freezing treatment of the imbibed seeds, the seed viability was 78% for weedy rice and 16% for cultivated rice. The deterioration of seed tissue induced by freezing treatment was observed by the tetrazolium test. In an accelerated aging test at low temperature and soaking conditions, the seed viability of the weedy rice was 40% higher than the cultivated rice 90 days after treatment. During accelerated aging of seeds, the protein content remained higher in the weedy rice compared to the cultivated rice, and fat acidity remained lower in the weedy rice compared to the cultivated rice. Catalase and superoxide dismutase activity of the weedy rice was 4 times higher than that of the cultivated rice, and DPPH radical scavenging activity of the weedy rice was also much higher than for the cultivated rice.ConclusionIn conclusion, the superior ability of seed wintering in weedy rice was based on freezing resistibility of embryo cellular tissue and higher antioxidant activity to protect seed deterioration during the winter season.Electronic supplementary materialThe online version of this article (doi:10.1186/1939-8433-5-21) contains supplementary material, which is available to authorized users.

Highlights

Incidences of weedy rice continuously occurred in paddy fields because its shattering seeds were able to over-winter
Wintering characteristics of weedy rice in the winter period may vary depending on the moisture state of the paddy surface
The results were almost identical to the first year experiment except that the seed viabilities significantly decreased in the flooded paddy as compared with the dry paddy field for both weedy rice (WD-3, PBR) and cultivated rice (Hopum, Ilpum)

Summary

Introduction

Incidences of weedy rice continuously occurred in paddy fields because its shattering seeds were able to over-winter. Weedy rice infestation increased significantly after shifting from rice transplanting to direct seeding, and it was recognized as a noxious weed (Ottis et al 2005; Suh 2003; Vaughan et al 2001). Weedy rice infestations have been reported to have spread to 40–75% of the total area of rice cultivation in Europe, 40% in Brazil, 55% in Senegal, 80% in Cuba, and 60% in Costa Rica (Fogliatto et al 2010). Weedy rice infestations are responsible for significant yield losses, which are severe in short varieties and late planting cultivation (Fogliatto et al 2010). Weedy rice is so productive that it can spread and cause major economic damage (Kane and Baack 2007), but it is impossible to control weedy rice during the rice cultivation period by herbicide because it belongs to the same species as the cultivated rice (Delouche et al 2007; Suh 2003)

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