SummarySeven homozygous transgenic lines of two European commercial cultivars of rice (Ariete (A) and Senia (S)), harbouring the cry1B or cry1Aa Bacillus thuringiensis ( Bt ) δ -endotoxin genes, were field evaluated for protection from striped stem borer (SSB) ( Chilo suppressalis ) of protection, with a notably low level of penetration of SSB larvae in the stems, but higher external symptoms than constitutive lines, probably due to the time lag to benefit from the protective effect of Cry1B.

Paddy rice fields are one of the most important sources of anthropogenic methane. Improving the accuracy in the CH4 budget is fundamental to identify strategies to mitigate climate change. Such improvement requires a mechanistic understanding of the complex interactions between environmental and agronomic factors determining CH4 emissions, and also the characterization of the annual temporal CH4 emissions pattern in the whole crop cycle. Hence, both the growing and fallow seasons must be included. However, most of the previous research has been based on single-factor analyses that are focused on the growing season. In order to fill this gap, a study was conducted in a Mediterranean rice agrosystem (Ebre Delta, Catalonia) following a farm-to-farm approach with the purpose of 1) evaluating the cumulative and temporal pattern of CH4 emission, and 2) conducting a multi-variate analyses to assess the associative pattern, relative contribution and temporal variation of the main explanatory variables concerning the observed CH4 emissions. Measurements of CH4 emissions and agronomic and environmental parameters in 15 commercial rice fields were monitored monthly, during a whole crop field cycle. The temporal pattern of CH4 emission followed a bi-modal distribution peaking in August and October. The cumulative annual CH4 emissions from rice fields amounted 314 kg CH4 kg ha-1, of which ca. 70% were emitted during the fallow season. The main controlling factors of the CH4 emission rate in the growing season were positive related to water level and plant cover, while soil redox was negatively related. The main controlling factors in the fallow season were water level (negatively related, conversely to the growing season), as well as straw incorporation and soil temperature (positively related). The results of this study highlight the importance of the often neglected fallow season in the accurate estimation of CH4 emissions and, thus, the necessity of measurement programs that cover the whole crop field cycle. This information is the first step for setting effective mitigation strategies based on straw and water management.

Rice tillering is a crucial stage for yield formation. Deep understanding of the relationship between tillering dynamics and yield formation in a particular agrosystem is crucial to boost rice productivity. Research on rice tillering is mainly focused on tropical agrosystems whereas less is done in the Mediterranean, with direct water-seeding and Japonica cultivars. This study aims at characterizing tillering dynamics and identifying the main explanatory tillering traits of yield in a Mediterranean rice agrosystem, Ebro Delta (Northern Spain). A temperate Japonica cultivar grown in Spain, Gleva, was utilized. Plants and tillers were tagged to assess emergence and fertility ratios and grain yield; while changes in tillering number over time, yield and yield components for unit area were measured. Plant and tillering dynamics in the Ebro Delta rice fields can be accurately predicted through equations herein provided, which are based either on thermal time or leaf development. Plants grown under regional standard agricultural practices produced up to eight primary tillers of which two or three become productive. Maximum tiller number was the main explanatory variable of yield while high-yielding tillers within a plant are located on nodes with the highest emergence ratios and, after the main stem, they are the major contributors to yield. The decisive role of tiller development on yield along with the predictability of tiller dynamics raises options to optimize grain yield through tillering modulation. In this sense, results from this study suggests the promotion of early tillering followed by inhibition of late tillering as a strategy of tillering regulation.Additional key words: Oryza sativa L.; tillering dynamics; tiller order; yield formation; emergence; fertility; curve fitting; synchrony

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