Rice is the second most important cereal in West Africa and is an essential element in the diet of the population. However, iron toxicity is one of the major edaphic constraints in lowland rice cultivation. The large amount of ferrous ions in solution causes an imbalance in nutrients involving a nutritional disorder affecting the growth of crops including rice. The present study conducted in 2014 in Guinea Conakry in the lowlands of the Kilissi Agronomic Research Station aimed to evaluate the effect of silica on reducing of the effect of iron toxicity in rice. Thus, rice varieties were evaluated according to a split plot device with three (3) randomized replications for two factors (rice varieties and silica doses) and three (3) silica treatments (D0 g, D120 g and D240 g). The results showed a significant effect of silica on most agronomic parameters of the rice varieties tested. The D240 g dose gave the
Rice is the staple food in the Republic of Guinea. However, its production is seriously hampered by iron toxicity. The fight against this stress necessarily involves the search for tolerant or resistant varieties. The study aims to determine quantitative trait locus (QTL) associated with tolerance to iron toxicity and to identify genotypes tolerant or resistant to iron toxicity. Thus, 90 local rice accessions collected in two regions of Guinea with high iron toxicity were evaluated using 33,537 single nucleotide polymorphism (SNP) markers. Seventy of the SNP markers expressed a polymorphism rate of 100%. Diversity analysis of the entire collection with these markers revealed a total of 140 alleles, a moderate Nei genetic diversity of 0.426, a fairly high Shannon diversity index of 0.610 and an organization of the accessions into four genetic groups. The study also identified 12 potentially iron-tolerant accessions and five QTLs associated with iron-toxicity tolerance located on chromosomes 1, 2, 3, 11, and 12. The 12 genotypes identified could be exploited in the lowland rice breeding program.
In Guinea, traditional rice varieties are the most widely cultivated in rural areas despite their low yield and high susceptibility to iron toxicity. Moreover, the introduction of new improved varieties tolerant to iron toxicity poses a serious threat to the preservation of the genetic resources of these traditional varieties, whose genetic diversity remains poorly known. The present study therefore aims at a better valorisation of these local rice cultivars through the evaluation of their agromorphological diversity and the identification of genotypes potentially tolerant or resistant to iron toxicity. Thus, 90 accessions collected in the regions of Kindia and Macenta and six controls susceptible or resistant to iron toxicity (AZUCENA, BOUAKE 189, CK 73, IR64, NERICAL 19 and AURYLUX 6) were evaluated in three replicate alpha lattice designs in two sites (Sérédou and Kilissi) using 16 agromorphological traits. The results showed significant agromorphological variability of the traditional accessions at both sites for all qualitative and most quantitative traits studied. In addition, 30 local cultivars expressed similar or higher grain yields than the resistant or tolerant controls at both sites, of which 12 were found to be stable at both sites. Of the 12 cultivars identified, five were resistant and seven tolerant to iron toxicity. These 12 accessions could be used in the varietal improvement of lowland rice in Guinea Conakry.
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