Physical and Pasting Properties of ‘Ofada’ Rice (Oryza sativa L.) Varieties

ABSTRACTIn this study, grain physical and pasting properties of ofada rice cultivated in South-West Nigeria was evaluated using Standard Evaluation System (SES) for rice with the aim of providing basic information for brand development and utilization of ofada in the development of novel food products. Results showed that size and shape of ofada rice ranged from 5.9 to 9.0mm and 1.8 to 3.0mm respectively. The 1000-grain weight was between 24.0 to 31.0g. Percentage hull was significantly different among the cultivars, ranging from 16 to 21. Peak viscosity ranged between 112.7 and 152.8 BU, minimum, setback and final viscosities varied from 80.3 to 117.2 BU, 104.0 to 143.3BU and 190.8 and 232.3 BU respectively. Gelatinization temperature was not significantly different and varied between 64.1 to 64.7°C. Significant difference (p<5%) was observed among the samples in terms of minimum setback and final viscosities respectively. Significant negative association was observed between kernel length and gelatinization temperature (r=– 0.65), setback and gelatinization temperature (r=– 67) while positive correlation was observed between breakdown viscosity and peak viscosity (r=0.86). The good pasting behaviour makes ofada flour good material for the production of stiff dough products, better palatability and water binding capacity while physical qualities give ofada an advantage during milling. This attributes could be exploited for the development of new varieties and utilization in food development of the ofada rice value-chain

Screening African rice (Oryza glaberrima) for tolerance to abiotic stresses: I. Fe toxicity

AbstractIron (Fe) toxicity is recognized as one of the most widely spread soil constraints for rice production especially in West Africa. Oryza glaberrima the cultivated rice species that originated from West Africa is well-adapted to its growing ecologies. The aim of this study was to identify the promising O. glaberrima accessions tolerant to Fe toxicity from the 2106 accessions held at the AfricaRice gene bank. The screenings were conducted over a four-year period and involved evaluating the entries under Fe-toxic field conditions in West Africa, selecting good yielding accessions and repeating the testing with newly selected lines. Three accessions (TOG 7206, TOG 6218-B and TOG 7250-A) were higher yielding than O. sativa checks under stress but with similar yields under control conditions. These accessions yielded over 300g/m2 under both Fe toxicity and control conditions. In conclusion, these materials could be used as donors in breeding programs for developing high yielding rice varieties suited to Fe toxicity affected areas in West Africa

Multiple small-effect alleles of Indica origin enhance high iron-associated stress tolerance in rice under field conditions in west Africa

Open Access Journal; Published online: 15 Jan 2021Understanding the genetics of field-based tolerance to high iron-associated (HIA) stress in rice can accelerate the development of new varieties with enhanced yield performance in West African lowland ecosystems. To date, few field-based studies have been undertaken to rigorously evaluate rice yield performance under HIA stress conditions. In this study, two NERICA × O. sativa bi-parental rice populations and one O.sativa diversity panel consisting of 296 rice accessions were evaluated for grain yield and leaf bronzing symptoms over multiple years in four West African HIA stress and control sites. Mapping of these traits identified a large number of QTLs and single nucleotide polymorphisms (SNPs) associated with stress tolerance in the field. Favorable alleles associated with tolerance to high levels of iron in anaerobic rice soils were rare and almost exclusively derived from the indica subpopulation, including the most favorable alleles identified in NERICA varieties. These findings highlight the complex genetic architecture underlying rice response to HIA stress and suggest that a recurrent selection program focusing on an expanded indica genepool could be productively used in combination with genomic selection to increase the efficiency of selection in breeding programs designed to enhance tolerance to this prevalent abiotic stress in West Africa

Screening African Rice (Oryza glaberrima) for Tolerance to Abiotic Stresses: II. Lowland Drought

Drought is a major constraint to rice (Oryza spp.) production in sub-Saharan Africa. Oryza glaberrima Steud., the cultivated rice species that originated from West Africa, is well-adapted to its growing ecologies. This study was initiated to identify promising O. glaberrima accessions tolerant to lowland drought stress from the 2106 accessions held at the AfricaRice Genebank. Screening was done over a 3-yr period in West Africa using standardized protocol and involved evaluating for grain yield under drought and/or irrigated conditions, selecting the high-yielding lines, and repeating the testing with the newly selected lines. Four accessions (TOG 7400, TOG 6520, TOG 6519-A, and TOG 7442-B) with consistently higher grain yield under drought stress and irrigated conditions were selected. These four accessions originated from three countries in West Africa, namely, Ghana, Liberia, and Nigeria. The selected O. glaberrima accessions could be used as donors in breeding for drought tolerance in rice

Processing characteristics, grain quality and end-use quality of hybrids and common improved rice (Oryza sativa L.) varieties from Nigeria

Grain quality characteristics of hybrids and some common improved rice (CIR) varieties were evaluated using standard evaluation techniques as a strategy for recommendation for release and use in various rice-based products. Paddy length varied between 8.22 to 10.53 mm in the hybrid and 9.28 to 9.70 mm in the CIR while paddy shape ranged from 3.56 to 4.94 and 3.95 – 4.49 in hybrids and CIR varieties respectively. Hybrids were lighter and less yellow than the improved inbred samples. Total milling recovery (TMR) was lower in hybrid than CIR and there was significantly (p &lt; 0.05) outstanding performance in terms of milling recovery of FARO 52 and FARO 60 over the hybrids. There was no significant difference (p &lt; 0.05) between the hybrid and CIR in terms of grain elongation ratio, but there was marginal difference in terms of elongation index. Water uptake ratio significantly (p &lt; 0.05) varied between 5.54 and 6.83 in CIR and 5.37 to 6.96 among the hybrids. Hybrids indicated lower cooking time than CIR. Correlation study of the relationship between physical and milling qualities indicated significantly (p &lt; 0.05) high negative correlation (r2 = –0.93) between TMR and percentage hull, while head rice recovery (HRR) compared with broken rice percentage indicated negative significant (p &lt; 0.05) correlation (r2 = –0.96). Lowest paste viscosity (431.17 cP) was observed in NG05 and highest (480.42 cP) in NG03, while 382.04 cP and 511.63 cP was the least and highest values in CIR lines respectively. This result will facilitate the adoption of hybrid rice in Nigeria and improvement of its marketability and application in different food formulations.Keywords: Rice, hybrids, milling quality, cooking quality, pastin

Screening African rice (Oryza glaberrima) for tolerance to abiotic stresses: I. Fe toxicity.

Iron (Fe) toxicity is recognized as one of the most widely spread soil constraints for rice production especially in West Africa. Oryza glaberrima the cultivated rice species that originated from West Africa is well-adapted to its growing ecologies. The aim of this study was to identify the promising O. glaberrima accessions tolerant to Fe toxicity from the 2106 accessions held at the AfricaRice gene bank. The screenings were conducted over a four-year period and involved evaluating the entries under Fe-toxic field conditions in West Africa, selecting good yielding accessions and repeating the testing with newly selected lines. Three accessions (TOG 7206, TOG 6218-B and TOG 7250-A) were higher yielding than O. sativa checks under stress but with similar yields under control conditions. These accessions yielded over 300 g/m2 under both Fe toxicity and control conditions. In conclusion, these materials could be used as donors in breeding programs for developing high yielding rice varieties suited to Fe toxicity affected areas in West Africa