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More issues need to be considered in molecular breeding of wheat

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A variety can not be a real pure line as one genotype in practice with traditional methods. The trans-gene and the gene introgressed via MAS are facing a serious challenge of background constraints. The gene of a Mendelian factor is much complicated than the gene of a DNA fragment. From a DNA fragment to a trait, a lot of essential elements are lost in modern molecular genetics.

23th, Aug, 2011, Perth,Australia

More issues need to be considered in molecular breeding of wheat

Haibo Wang

Plant Genetic Engineering Center, Institute of Genetics and Physiology, Hebei Academy of Agriculture and Forestry Science, Shijiazhuang, China 050051

At the first Australia-China Wheat Genetics and Breeding Workshop (ACWGBW) held in Beijing in May 24-26, 2010, I gave a talk entitled “Problems need to be considered in molecular breeding of wheat“, In which, I mentioned: (1) A variety can not be a real pure line as one genotype in practice with traditional methods. Usually, the conclusion of genetics from near-isogenic lines developed with such kind of recurrent parents is not surely precise. (2) The trans-gene and the gene introgressed via MAS are facing a serious challenge of background constraints. Not every gene will certainly express its function as breeders expected in a new background. The study of gene sociology is badly needed. (3) The gene of a Mendelian factor is much complicated than the gene of a DNA fragment. From a DNA fragment to a trait, a lot of essential elements are lost in modern molecular genetics. In general, a DNA fragment is not equal to a Mendelian factor.

In this ACWGBW, I continue to discuss the issues that should be paid attention to:

1) The practicability of the molecular marks. Many DNA markers published in literature have not any real linkages with the target traits. They can not be used as selection markers for molecular breeding. It is difficult to determine whether or not the molecular markers are linked with the concerned traits through the traditional practice to create genetic populations. The practicability of DNA markers have to be validated and confirmed by backcrossing, and/or gene pyramiding.

2) The authenticity of genetic linkage. The cooperation of the genes in physiological level for survival of individuals, which called “physiological linkage”, is stronger than the physical linkage of the genes along chromosomes. Housekeeping genes are actually linked together through physiological mechanisms. Although there are different alleles of these genes and different combination of the alleles can show different levels of vitality, plant breeding does not specifically evaluate and select such kind of gene combinations. Generally, the traits can be selected in breeding are “neutral mutations or variations” or even “unfavorable mutations or variations for plant but can be compensated by cultivation”. Breeders need to have insights and imaginations for sagacious selection. Molecular markers are necessary for traits that are not easily judged by naked eyes, but full genome scan is not necessary. Expensive genome-wide scan should be used to carry out gene-sociological studies, but the correct design of the research is a prerequisite.

3) The difference between conventional breeding and molecular breeding. Conventional breeding is focused on the selection of integrated performance rather than specific features after hybridization in every step. A new cultivar is selected via a synthetic selection or intercross/selection. While molecular breeding is firstly to select a number of materials/lines must-having specific markers/traits as basic materials, and then to compel the objective genes or traits/markers to be pyramided to an expected variety by molecular design. The focus of molecular breeding and traditional breeding is different, and in a strict sense these two methods are irreplaceable. Molecular breeding should be combined with or embedded into conventional breeding and play a complementary role.

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