Divergent recurrent selection for starchiness in a population homozygous for recessive su1 has revealed significant levels of endogenous variation for kernel and endosperm traits. Selection was based on visual evaluation of kernels on the ear. After six cycles of selection, mature endosperm from the pseudostarchy population contained 17% more starch, 50% less water soluble polysaccharide, 83% less sucrose, and 93% less glucose than the extreme sugary population. An evaluation of the genetic control of pseudostarchiness revealed three unlinked QTL accounting for approximately 30% of the phenotypic variation. The gene action of these QTL was primarily additive. Several QTL associated with endosperm carbohydrates, protein, and oil overlapped with starchy appearance. Visual endosperm starchiness was significantly correlated with starch (r = 0.50), phytoglycogen (r = -0.44), sucrose (r = -0.45), glucose (r = -0.56), and oil (r = -0.55). There was no significant correlation between visual endosperm starchiness and protein, and thus it appears that protein accumulation was not necessarily reduced at the expense of starch. In a separate experiment, RNA from cycle six pseudostarchy and cycle six extreme sugary was interrogated on maize spotted micro-arrays at four day intervals from 2 to 18 days after pollination (DAP). RNA collected at two and six DAP included whole kernels, while 10, 14, and 18 DAP included only endosperm. Unique time course transcriptional profiles involving starch and protein synthesis were resolved. Differentially expressed genes included Brittle2, Sugary2, Amylose extender1, and many encoding zein proteins. This research provides information on the genetic and molecular effects of modifying genes which are revealed in the presence of the qualitative mutation, sugary1.Total sugars were extracted in a solution of 80% ETOH, and sucrose, glucose, and fructose were quantified via HPLC ... The HPLC system was an Agilent 1200 series chromatography system, with refractive index detector (model G1362A), anbsp;...
|Title||:||Endogenous Variation Revealed by Selection in Sugary1 Maize (Zea Mays L.)|
|Author||:||Michael Adam Chandler|
|Publisher||:||ProQuest - 2008|