Methane emission and its relations with plant parameters and dissolved oxygen in different rice genotypes

The effect of growth parameters, aerenchyma gas spaces and dissolved oxygen (DO) in rice genotypes on CH4 emission was examined to develop crop management strategies with low emitting rice lines while sustaining high yield. A total of 35 lines were studied in two sets of two experiments in completely randomized design. The mean CH4 emission was highest in rice line IR 73688-82-2-3-2-2, and the lowest with line 96010-TR 1749-1-2-1-1. For the other rice genotypes an intermediate CH4 emission at the average of 0.41 mg plant(-1) day(-1) was observed. There were significant differences in yield and growth parameters between the genotypes tested. This finding shows that the use of selected lines, such as IR 72 and Sakha 101 for rice breeding program, can potentially lower CH4 emission (0.33 and 0.48 mg plant(-1) day(-1)) without scarifying yield. Correlation analysis showed that CH4 flux was significantly related with root weight, shoot dry weight, number of plant tillers and leaf area. Statistical analyses showed also that the negative correlation was significant (p < 0.001) between the methane emission and dissolved oxygen content of rhizosphere. However, CH4 emission had significantly positive correlation (p < 0.01) with the number of aerenchyma gas spaces. The wide variation of the above traits and related emission rates among genotypes opens the possibility for breeding rice cultivars with low methane emission potential.