X. Sha

Rice artificial hybridization for genetic analysis.

Artificial hybridization has probably been practiced since ancient time; however, the science of genetics did not initiate until Gregor Mendel conducted a series of crosses between different pure lines of garden pea and made careful observations and systematical analyses of their offspring. Artificial hybridization or crossing between carefully chosen parents has been and still is the primary way to transfer genes from different germplasm for self-pollinated rice. Through gene recombination, novel genetic variation is created by different arrangements of genes existing in parental lines. Procedures of artificial hybridization involve the selection of appropriate panicles from representative plants of the female parents, the emasculation of female parents, and the pollination of emasculated panicles with abundant pollens of selected male parents. Of the numerous proposed methods, hot water and vacuum emasculation have proven to be the most robust and reliable ones. A successful and efficient hybridization program also relies on the knowledge of parental lines or germplasm, the reproductive biology and development of rice, the conditions needed to promote flowering and seed development, and the techniques to synchronize flowering of diverse parents.

Visual Estimation of Rice (Oryza sativa L.) Grain Yield in Multiple Environments in Louisiana

Development of high-yielding rice (Oryza sativa L.) cultivars is a primary objective of most rice-breeding programs, and breeding progress is generally measured through increases in grain yield attributable to new cultivars. The pedigree-breeding method, commonly employed in rice-breeding programs, usually results in a large number of lines being discarded in early generations on the basis of visual estimates of grain yield potential. The objective of this research, conducted at five locations in 2007 and 2008 in Louisiana, was to evaluate the effectiveness of visual grain-yield predictions by two rice breeders. A second objective was to determine the effect of disease and lodging on the accuracy of visual selection. Across all years and locations, the grain yield estimates of both breeders were positively correlated with observed grain yield, indicating that visual selection for grain yield can be effective. Differences existed in the predictive ability of the breeders to estimate grain yield at different environments. Generally, breeders were more accurate in visually estimating grain yield when the standard deviation of the estimates was high, indicating that perceived phenotypic expression of grain yield is an important factor affecting the visual estimation of yield potential. Locations with high disease pressure and lodging resulted in a greater standard deviation of the yield estimates and improved the accuracy of visual estimation of grain yield.