Monday, November 13, 2006

Evaluating Rice Cultivar Mixtures for Yield and Yield Stability.

Sterling Blanche, Louisiana State Univ, AgCenter, Rice Research Station, 1373 Caffey Rd., Rayne, LA 70578 and Steve Linscombe, Louisiana State Univ, AgCenter, Rice Research Station, 1373 Caffey Road, Rayne, LA 70578.

Research was conducted in 2006 to evaluate grain yield and yield stability of hybrid and varietal rice cultivars as monocultures and cultivar mixtures.  Genotype x environment interactions exist when the responses of two cultivars to multiple environments are unequal.  A stable cultivar is one that shows little response to environmental variation by exhibiting consistent performance in multiple years and locations.  There are two general ways in which yield stability can be achieved:  a) employing multiple genotypes adapted to a range of environments (heterogeneity), or b) the individual cultivar may be well-buffered against a range of environments.  It is difficult for breeders to incorporate in one high-yielding genotype all of the traits necessary for yield stability.  Cultivar mixtures may improve yield stability through genotypic diversity.  In the present study, two varieties (Cocodrie and URN152) and two hybrids (XP723 and CLXL730) were grown at seven locations in Louisiana in a monoculture and in 50/50 (two component) mixtures.  The 50/50 mixtures were derived by including each variety and hybrid at 50% of its recommended seeding rate.  The 10 treatments were two varieties in monoculture (homozygous, homogeneous), b) two hybrids in monoculture (heterozygous, homogenous), c) a variety mixture (homozygous, heterogeneous), d) a hybrid mixture (heterozygous, heterogeneous), and e) four variety and hybrid mixtures (homozygous and heterozygous, heterogeneous).  Data presented will include evaluations of plant stature, crop maturity, and grain and milling yield.  GGE Biplot Pattern Explorer, an application that allows cultivars and cultivar mixtures to be simultaneously evaluated for yield and yield stability, will be used.