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Lowland rice {Oryza sativa L.) is often affected by iron toxicity, which may iead to yield losses. One important constraint in the study of the inheritance of resistance strategies to this stress is the inconsistency of gene expression across different environments. This study aimed to determine the stability of quantitative trait loci (QTL) across several environments. Quantitative trait loci mapping for traits related to resistance mechanisms had been previously performed using 164 recombinant inbred lines derived from 'Azucena' and 'IR64' screened in hydroponics in a phytotron. In the present study, this population was tested under excessive ferrous iron conditions in three additional environments: in hydroponics in a greenhouse, on washed sand, and in the field. Altogether, 44 putative QTL were identified in the four single QTL analyses for morphological, physiological, and agronomic traits. From these 44 QTL, 20 were found in overlapping regions for the same or related traits in different environments, identifying six genomic regions of great interest for the inheritance of resistance to iron toxicity. Quantitative trait loci stability across environments was also checked by performing a joint QTL analysis, which confirmed the position of nine QTL previously found in the same or adjacent regions by at least one single analysis. Combining both single and joint analyses helps in separating QTL specific to a particular environment from generally expressed ones thus is more suitable for marker-assisted selection.

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L'effet de cinq classes de diamètre du houppier du karité sur les paramètres agronomiques a été étudié en comparant les zones sous houppier et hors houppier en zone soudanienne du Bénin. L'humidité pondérale et la température du sol et les rendements grains et paille du maïs ont été mesurés. La présence des arbres de karité a eu une influence significativement (P< 0,01 à P< 0,001) positive sur l'humidité pondérale et la température du sol de façon croissante avec la largeur du houppier. Les teneurs du sol en C-organique, Ntotal et Ca 2+ échangeable sont élevées sous houppier comparativement à la zone hors houppier. Cependant, les rendements sous houppier sont significativement (P< 0,05) faibles comparativement à la zone hors houppier. Les classes de diamètre du houppier n'ont pas influé significativement la production de grains et de paille du maïs. Les rendements grain et paille sous houppier sont réduits respectivement de 46,6% et de 32,8% comparativement à la zone hors houppier. On note une influence positive du système agroforestier à karitésur l'humidité pondérale, la température du sol, le carbone organique et l'azote total, mais un effet négatif est noté sur les paramètres de rendement du maïs.

Abstract. The latest version of RegCM4 with CLM4.5 as a land surface scheme was used to assess the performance and sensitivity of the simulated West African climate system to different convection schemes. The sensitivity studies were performed over the West African domain from November 2002 to December 2004 at a spatial resolution of 50 km × 50 km and involved five convective schemes: (i) Emanuel; (ii) Grell; (iii) Emanuel over land and Grell over ocean (Mix1); (iv) Grell over land and Emanuel over ocean (Mix2); and (v) Tiedtke. All simulations were forced with ERA-Interim data. Validation of surface temperature at 2 m and precipitation were conducted using data from the Climate Research Unit (CRU), Global Precipitation Climatology Project (GPCP) and the Tropical Rainfall Measurement Mission (TRMM) during June to September (rainy season), while the simulated atmospheric dynamic was compared to ERA-Interim data. It is worth noting that the few previous similar sensitivity studies conducted in the region were performed using BATS as a land surface scheme and involved less convective schemes. Compared with the previous version of RegCM, RegCM4-CLM also shows a general cold bias over West Africa whatever the convective scheme used. This cold bias is more reduced when using the Emanuel convective scheme. In terms of precipitation, the dominant feature in model simulations is a dry bias that is better reduced when using the Emanuel convective scheme. Considering the good performance with respect to a quantitative evaluation of the temperature and precipitation simulations over the entire West African domain and its subregions, the Emanuel convective scheme is recommended for the study of the West African climate system.