Identification and Selection of Promising Donor Genotypes

to do backcrossing and producing F 2 seeds. Planting of mapping populations were conducted during Dry Season of 2007. Hybridization and maintenance of the crossed plants until harvesting were done in the screen house. Deoxyribo Nucleic Acid DNA of the parents and mapping population was extracted in Dry Season 2007. Deoxyribo Nucleic Acid sample of parents were used for screening of polymorphism using SSR markers. Deoxyribo Nucleic Acid sample of the individuals of mapping populations was used for genotyping using selected polymorphic markers. Sample preparation and measurement of iron and zinc content was done in Dry Season of 2008. Field experiment was conducted at IRRI International Rice Research Institute Experimental Farm. Molecular analyses were done in GAMMA Gene Array and Molecular Marker Application Laboratory, and measurement of iron content using colorimetric method was done at Irrigated Rice Breeding Group Laboratory and ASL. The field was located at IRRI campus, Los Banos. It was located at latitude of 14 o North, longitude of 121 o East, and at an elevation of 21 meter above sea level. Weather data were collected when the mapping populations were planted December 2006 to June 2007. The average rainfall during that period was 67.83 mm. The maximum, minimum, and mean of the daily temperature were 33.4, 25.1, and 29.3 o C respectively. The day length was between 11.2 and 12.8 hours during this period. The average humidity was 83.72. The maximum wind flow was 2.8 ms -1 during January to April 2007 Climate Unit, Crop and Environment Science Division, IRRI. Tungro incidence was observed in the F 2 mapping population. The infected seedlings were removed and plant protection was provided as needed in coordination with Experimental Farm Office.

3.2. Identification and Selection of Promising Donor Genotypes

Background Starting mid 1990s various brown rice samples were analyzed for various minerals including iron and zinc content by Inductively Coupled Argon Plasma Atomic Emission Spectroscopy ICP-AES. However, rice is consumed primarily in the polished state hence it would be more appropriate to study the genetic 16 variation for iron and zinc content in the polished rice grains. Therefore, IRRI shifted its entire screening work to polished rice starting 2004. Scientists at IRRI evaluated 15 promising genotypes in replicated trials at two locations IRRI, PhilRice Maligaya and in 3 seasons 2004WS, 2005DS, 2005WS. The range of average iron content in the polished rice was from 2.97 to 7.4 ppm with an average of 4.75 ppm, while for zinc content the range is from 14.33 to 23.26 ppm with an average of 20.02 ppm. These results suggested that ample genetic variation exists in the germplasm and it would be worthwhile to breed for enhancing the iron and zinc content in the rice grains Virk et al. 2006; 2007. Selection of Donor Genotypes A total of twelve rice genotypes were used in this study Table 1. Four promising elite breeding lines namely IR75862-206-2-8-3-B-B-B, IR69428-6-1-1- 3-3, IR68144-2B-2-2-3-1-166 and IR68144-2B-2-2-3-1-127 were identified from a multi-environmental evaluation study by Virk et al. 2006; 2007. Two popular indica varieties namely IR64-released in 1985 and PSBRc82 IR64683-87-2-2-3-3- released in the Philippines in 2000 were also included as potential recipient genotypes. In addition 2 temperate japonica varieties namely Joryeongbyeo and Areumbyeo with high zinc content Virk et al. 2006 and 3 nutritionally known Korean rice varieties namely Heugjinjubyeo, Baegjinjubyeo and Goami2 Lee et al. 2006; 2007. Lastly, a promising entry namely Zuchein from China possessing high iron and zinc content in the brown rice was identified from previous screening conducted at IRRI Gregorio, Personal communication was also included in this study.

3.3. Materials