Project Number: 6225-21000-010-19
Start Date: Mar 01, 2011
End Date: Feb 28, 2016
1. Germplasm quarantine: A total of 600 recombined inbred lines (RILs), 300 each for Nipponbare (NB)/HEG4 and HEG4/HG4, will be introduced in four sets (150 per set) and processed through quarantine regulated by the USDA APHIS, Beltsville, MD, for insect and disease prevention. The quarantined seed will be used for evaluation of maturity, height, and cold tolerance, and DNA extraction for study on mPing. 2. Seed stock preparation: Over the course of the project, seed of 600 RILs released from the quarantine program and 1,000 mPing mutagenesis lines using the U.S. cultivars will be increased in field for sufficient seed using single hill for a plant strategy. One plant will be selected from each line for DNA extraction and stock seed source, and the rest of the plants similar to the selected one will be bulk-harvested for the evaluation. 3. Evaluation of days to flower and plant height: The harvested bulk seed of 600 RILs and 1,000 mPing lines will be in single row plot and two locations, AR and TX, three replications arranged with a Randomized Complete Block Design (RCBD) in each location. Each replication will include cultivar 'Rondo' and 'Presidio' as standard checks for monitoring environmental influence. The date when 50% of seedlings emerge above the ground surface 1 cm in the test field will be recorded for conversion of the days to flower. Right before harvesting, height from the ground surface to the tip of panicles will be measured from the center of plot as an estimate of plant height. Data will be statistically analyzed. 4. Evaluation of cold tolerance: The harvested bulk seed of 600 RILs and 1,000 mPing lines will be used for cold tolerance evaluation using method described by Andaya and Mackill (2003) with some modifications. Six seeds of each line will be sown in 98-cell plug flats. Each flat will include 'Zhe733' and 'PI560281', cold susceptible and tolerant checks, respectively. Lines in each flat will be arranged using the RCBD with three replications. The flats will be placed in a greenhouse at 27 C until the seedlings reach the 3-leaf stage before a cold treatment at 10 C constantly with 12 h light period and 70% relative humidity. Plant reaction to cold stress as exhibited by necrosis and/or wilting will be scored using the scale of 1 (tolerant) to 9 (susceptible) when Lemont reaches 9. Data of the score will be statistically analyzed. 5. Establishment of a germplasm collection: After measuring plant height in the evaluation field, the first replication of 600 RILs and 1,000 mPing lines in AR will be harvested as seed source to form the rice germplasm collection. Each step will be cautiously operated to avoid seed contamination. Each line will be manually cut using a sickle, bundled using a rope, and threshed using Almaco Thresher. The thresher will be thoroughly blown using compressed air after each line and the seed in paper envelop will be air-dried to 12% of humidity content. The dried seed will be well cleaned using Clipper seed cleaner blown by compressed air after each line and then deposited in the USDA Genetic Stocks – Oryza (GSOR) Collection.