Rice Cultivar 'M-205'

Rice Experiment Station

‘M-205’ Rice

Origin and Breeding History of the Variety


M-205 is an early, semidwarf, California glabrous, Calrose quality medium-grain experimental line that has been evaluated in large plot yield tests since 1994.  It was tested under the experimental designation 94-Y-615. It is an early selection from the 1989-1990 winter greenhouse cross R16377 and has the pedigree 90-Y-63/M202, thus the full pedigree is M-201/M7//M-201/3/M-202. M-205 was developed by the California Cooperative Rice Research Foundation (CCRRF) at the Rice Experiment Station (RES), Biggs, CA.  All varieties used to develop M-205 are considered Calrose medium-grains with semidwarf height.  90-Y-63 was an early experimental line tested in statewide tests in 1989 and 1990 and has the pedigree M-201/M7//M-201. M-202 is the only variety currently in commercial production in California.  M-205 is the product of modified pedigree breeding. Early panicle selections from the 1991 F2 nursery were bulked 6 panicles per row in the 1991-1992 Hawaii Winter Nursery.  Panicle selections grouped from the R16377 Hawaii rows were planted in the 1992 RES individual rows.  The 1992 row 9161 was identified as the source of 1993 small plot 1165 which produced seed for 94-Y-615 entry in the RES Preliminary Yield Trial.  It has been tested in the University of California Cooperative Extension (UCCE) Statewide Yield Tests, 1995 to 1999.

Selection and multiplication

M-205 selection criteria were for shorter height and improved resistance to lodging. Panicle selections were first taken for headrows produced in 1995 and continued through 1999.  The 1995 panicles were initially purified in the 1995-1996 Hawaii Winter Nursery and in 1996 headrows at RES.  Panicle selections were taken in 1997 from the bulk seed of the 1996 headrows and advanced to the 1997-1998 Hawaii Winter Nursery.  The 1997-1998 Hawaii rows were bulked to plant the 1998 breeder seed and Hawaii panicle used to plant 158 headrows.  The 1998 breeder seed was used to plant the 1999 foundation seed and the bulk of the headrows planted the 1999 breeder production area. The 1998 headrow panicle selections were used to plant 400 headrows in 1999. 

Uniformity and stability

Panicle selections were first taken for headrow production in 1995 and continued through 1998. During the headrow production any putative segregating or variant rows were removed from the field. Visual inspection (seedling vigor, heading date, plant height, grain shape and size, etc.) of headrows were used as criteria to confirm cultivar purity. This is standard procedure at RES to monitor and maintain breeder seed of the 13 currently grown California rice varieties. M-205 was approved for certification by the California Crop Improvement Association in 2000. Classes of seed will be breeder, foundation, registered, and certified seed produced in California. Foundation seed can be used to produce foundation seed if necessary and headrow and breeder seed will be produced in foundation fields as necessary to maintain cultivar purity. M-205 has been observed in seed increase and production fields for five generations (1996 to 1999) and found to be uniform and stable.


The breeder, foundation, and headrows were rogued multiple times and off-types, putative out crosses, and other visual variants were removed from the field.  These included later, taller, smooth medium-grains, red apiculus longer medium-grain out crosses, pubescent medium-grain of M-205 maturity, smooth tetraploids and one late fat short-grain in a total frequency of 0.15% in the 1998 breeder field and 0.03% in 1999 foundation field.

Statement of Distinctiveness

Variety Differences

M-205 is a semidwarf, early maturing, medium-grain being released to serve the Calrose medium-grain market. “Calrose” was the founding California medium-grain rice variety, the ancestor of California medium-grains, and is now recognized as a market class term for California medium-grain rice. Comparisons for evaluation purposes were made to M-202, which is the predominant California medium grain. M-205 is shorter in height and has improved resistance to lodging when compared to M-202. M-205 is most similar to M-202 and is distinguished by it’s shorter height and improved resistance to lodging.