No abstract

Weedy rice is a serious problem in Uruguayan rice fields since intensification of rice production started about 10 years ago. The genetic diversity of 26 weedy accessions of weedy rice and 6 Uruguayan cultivars were analyzed using AFLP (amplified fragment length polymorphisms) methodology. Abundant polymorphisms were found among samples tested. Using different methods of analysis three groups of samples were revealed. A relationship was found between three groups and morphological traits. One group had a black hull, purple apex and long awn (wild type traits) while another group had straw hull and apex, and short or no awn (domestication traits). The third group included the cultivars analyzed and some weedy rice samples. The weedy rice in this third group is presumed to most closely mimic cultivated rice and may have recently evolved. The results suggest that weedy rice adapts either to the natural environment or to cultivation. The former type with black hull and long awn may be easy to control because it can easily be seen. The later group may be difficult to control, particularly since the weedy rices within the cluster consisting of cultivars suggest that weedy rices are continually evolving in Uruguayan rice fields. The AFLP technique is very effective for assessing genetic diversity within weedy rice and will be very useful for fingerprinting of local cultivars of rice.

No abstract

No abstract

The burgeoning demand for rice in Latin America and Caribbean (LAC) exceeds supply, resulting in a rice deficit. To overcome this challenge, rice production should be increased, albeit sustainably. However, since rice production is associated with increases in the atmospheric concentration of two greenhouse gases (GHGs), namely methane (CH 4) and nitrous oxide (N 2 O), the challenge is on ensuring that production increases are not associated with an increase in GHG emissions and thus do not cause an increase in GHG emission intensities. Based on current understanding of drivers of CH 4 and N 2 O production, we provide here insights on the potential climate change mitigation benefits of management and technological options (i.e., seeding, tillage, irrigation, residue management) pursued in the LAC region. Studies conducted in the LAC region show intermittent irrigation or alternate wetting and drying of rice fields to reduce CH 4 emissions by