Characteristics of Iron Tolerant Rice Lines Developed at IRRI under Field Conditions

Abstract

In the 2003 wet season, IR64 (check variety) and four lines of rice (Oryza sativa L.) developed at IRRI were cultivated in a field with iron (Fe) toxicity at Iloilo City, Philippines, and also under normal soil conditions at IRRI farm. Two of the lines used in the experiments were the near isogenic lines (NILs) of IR64, selected as Fe-tolerant lines in solution culture in the greenhouse. The other two lines were elite breeding lines that were selected as Fe-tolerant lines in the field trial at Iloilo. The tolerances of NILs were not expressed at the Iloilo field site because the yield reductions due to Fe-toxicity were similar to or larger than those for IR64. The yield reduction of elite breeding lines was smaller than that of IR64, indicating that the tolerance of elite breeding lines was expressed at the Iloilo field. At Iloilo, the shoot dry weights of IR64 and its NILs hardly increased after 73 days of cultivation. On the contrary, those of elite breeding lines kept on increasing. While the root dry weight of IR64 and its NILs decreased abruptly after 50 days of growth, those of elite breeding lines remained constant or decreased gradually. This finding suggests that one of the factors that suppressed the growth of IR64 and its NILs during the late stage was early root senescence. Since the tolerance of elite breeding lines was associated with the maintenance of root activity during the late stage of growth, the long maturity period of elite breeding lines presumably helped to alleviate the toxicity.Discipline: Soil, fertilizers and plant nutrition Additional key words: Fe-tolerance, Fe-toxicity, paddy soil, root JARQ 42 (3), 187 -192 (2008) http://www.jircas.affrc.go.jp This study was supported by the IRRI-Japan collaborative research project phase IV (1999IV ( -2004.

Soil-based screening for iron toxicity tolerance in rice using pots

“…Secondly, there is a strong correlation between LBS and grain yield as seen in this study at 60 DAS and several others Audebert & Sahrawat, 2000;Elec et al, 2013;Onaga,Edema, & Asea, 2012). However, in some other studies no significant correlation between LBS and grain yield was observed (Nozoe et al, 2008;Sahrawat et al, 1996) as seen at 40 and 80 DAS. Level of correlation between the two traits is likely to depend on stress intensity, testing condition, and type of varieties used.…”

“…The reasons for the observed differences in performance of Bao Thai in the two field studies are not clear but it could be due to differences in soil type. While Elec et al (2013) observed good correlation between hydroponic screening and field testing others have not found similar results (Becker & Asch, 2005;Nozoe et al, 2008).…”

Suppressive effect of rice bran incorporation in paddy soil on germination ofMonochoria vaginalisand its relationship with electric conductivity

“…Thus, one of the factors that caused an increase in EC might have been an increase in the organic acids and Fe 2þ contents of the soil solution. The amount of Fe 2þ in soil solution tends to be high when the pH of the soil is low, because Fe 2þ in soil solution precipitates as various oxides and hydroxides at high pH (Nozoe et al 2008). The findings obtained in this study suggest that soil pH is one of factors responsible for EC.…”

“…A high concentration of Fe 2þ in soil solution sometimes suppresses the growth of paddy rice (Nozoe et al 2008). In our previous papers, we suggested that the accumulation of Fe 2þ in soil solution was one of the factors related to the growth suppression of paddy weeds (Nozoe et al 2009;Nozoe et al 2010).…”

Genetic Improvement of Iron Toxicity Tolerance in Rice-Progress, Challenges and Prospects in West Africa

“…Audebert and Fofana (2009) reported that for every increase in LBS by one grain, the yield is reduced by 500 kg ha -1 . There are a few other reports of a negative correlation between bronzing score and yield under Fe toxicity stress (Sahrawat et al, 1996;Nozoe et al, 2008;Onaga et al, 2013). The relation between LBS and grain yield could depend on the type and number of entries used, and experimental conditions.…”