GENETIC MODIFICATION OF RADIATION USE EFFICIENCY IN BREAD WHEAT

T.Al-Assafi, Radhi

	GENETIC MODIFICATION OF RADIATION USE EFFICIENCY IN BREAD WHEAT
The Iraqi Journal of Agricultural Science
Article 1, Volume 40, Issue 6, 2009, Pages 62-77
Author
Radhi T.Al-Assafi
Abstract
In this reveiw, most important factors affecting radiation use efficiency (RUE) of wheat yield and some traits related were discussed . RUE of a crop is a function of several interacting physiological phenomena, each of which can be discussed independently from the point of view of genetic improvement .There is no a large increase in RUE by plant breeder but, the theoretical calculations state that a wide scale for improving it . Selection for higher rates of leaf photosynthesis at saturating light intensities (Amax) has not resulted in improved RUE of crops, perhaps most leaves in a canopy are not light-saturated . Genetic transformation of Rubisco to double its specificity for CO2 would theoretically increase Amax by 20% , and some evidence suggests that photosynthesis at sub-saturating light intensities would also be improved , especially by manipulation of leaf angle or by optimum distribution of leaf-N throughout the canopy. Improved RUE may be achieved by increasing sink demand (kernel number) if excess photosynthetic capacity exists during grain filling, as suggested by a number of studies in which source–sink balance was manipulated. Balancing source-and sink-strength is a complex genetic challenge since a crop will change between source and sink limitation as conditions vary during the day.Selection for superior segregants can be accelerated using rapidly measured physiological selection traits, such as stomatal conductance or canopy temperature depression . The genetic control of photosynthetic regulation may be explained in the future through the application of genomics

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