关键词: 谷氨酰胺, 谷氨酰胺, 肉仔鸡, 中枢淋巴器官, 胚后发育, 组织结构

Abstract: Since tradition breeding (eu-selection method) developed to ordinary breeding (cross) then to modern breeding (gene engineering, molecular breeding), breeding developed from one art to the science. Breeding is a science more than an art today. Breeding is a philosophy with high abstraction and integration and a science with high-level theory and art. Breeder must be a specialist in discovering and utilizing key genes and creating new genotypes. Selecting and crossing parents and selecting good offspring are the key art in the breeding program. Breeding is the eugenics in the environment science, and is the economics in the ecology science. Eight principles are suggested for crop breeding as follows: overcoming the key limit factor for high yielding, high yielding，stable yielding, widely compatibility, high efficiency use of every kinds of natural resources，meeting the need for society, adapting to ecology selection and innovating in the evolution. Breeding science needs to be innovated and developed continuously in future. We should put more attention on reasonably utilizing and combing with every kinds of breeding technology, developing and enhancing the level of science and art of breeding, increasing the selecting efficiency in crop breeding, and selecting more excellent crop varieties.