M. Sié

ABSTRACT Multivariate analysis is based on a statistical principle involving observation and analysis of more than one statistical variable at a time. The variability of 434 accessions of rice ( Oryza sativa L.) germplasm from Côte d'Ivoire was evaluated for 10 agro‐morphological traits in upland conditions at M'bé, Côte d'Ivoire (7°5′ N, 5°1′ W) in 2002 using augmented experimental design and analyzed with multivariate methods. The unweighted pair group method of the average linkage (UPGMA) cluster analysis, canonical discriminant analysis, and principal component analysis (PCA) were used to analyze the data obtained. This enabled the assessment of the extent and pattern of variation of the germplasm and identification of the major traits contributing to the diversity. Seven cluster groups were obtained from the 10 agro‐botanical traits using the UPGMA. Canonical discriminant analysis showed the contribution of each trait to the classification of the rice accessions into different cluster groups. The first three principal components explained about 72.24% of the total variation among the 10 characters. The results of canonical discriminant analysis and PCA suggested that traits such as plant height, number of days to heading and maturity, tillering ability, and grain size (weight, length, width, and shape) were the principal discriminatory characteristics. It was concluded that variation exists in the germplasm, which provides opportunities for this collection to be useful for genetic improvement.

ABSTRACT Lowland rice ( Oryza sativa L.) is often affected by iron toxicity, which may lead 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.

(eds M.C.S. Wopereis et al.) 1 membership to 17. When it was realized that WARDA’s products were gaining ground in countries beyond its traditional mandate region of West and Central Africa, the name Africa Rice Center was adopted in January 2003 (WARDA, 2004). In 2007, a new vision was formulated to encourage such countries to become full members of the Association. This prompted five more countries to join in the midst of the global food crisis of 2007–2008 (Central African Republic, the Democratic Republic of Congo, the Republic of Congo, Egypt and Uganda). These were followed by Gabon (September 2009) and Madagascar (February 2010). Thus, today (June 2013) the Association’s 24 member states represent West, Central, East and North African regions. When Africa Rice Center became the official legal name of the Center and the Association in 2009, the abbreviation AfricaRice was adopted in both English and French and was to be applied retroactively.1 Like other CGIAR-supported centres, AfricaRice has a Board of Trustees composed of nominees from member states and from Introduction