การเพิ่มปริมาณทริปโตแฟนด้วยยีน opaque-2 ในข้าวโพดข้าวเหนียวร่วมกับการใช้เครื่องหมายโมเลกุลช่วยในการคัดเลือก

Abstract

Crosses were made between waxy corn and quality protein corn as female and male parents, respectively. In segregating progenies of two crosses, Kwi no.1 x PopII no.53 and Kwi no.9 x PopII no.53, selfing and backcrossing methods were used and then marker-assisted selection of opaque-2 gene (o2o2) by phi057 and umc1066 and of waxy (wxwx) by phi022 and phi061 were applied to obtain the opaque-waxy corn (o2o2wxwx). For the first step of MAS, phi057 and umc1066 were employed to detect the opaque-2 gene (o2o2) in both of BC1S1 and S1 generations. The genotypic ratio of opaque-2 gene (O2O2:O2o2:o2o2) was 37:46:31 for BC1S1 and 42:146:42 for S1 from the cross of Kwi no.1 x PopII no.53 while it was 41:51:41 for BC1S1 and 41:169:35 for S1 from the cross of Kwi no.9 x PopII no.53. Only the genotypic of o2o2 plants were advanced generation to BC1S2 and S2. For the second step of MAS of the advanced generation, phi022 and phi061 were applied to detect the waxy gene (wxwx) to obtain the double homozygous recessive plant of both genes (o2o2wxwx). Finally of line selection, 5 lines of backcrossing and 6 lines of selfing methods were selected and tryptophan content in endosperm was analyzed by the glyoxylic acid method. The most importantly, the percentage of tryptophan content in endosperm of these selected lines ranged from 0.58 to 1.24 that higher than the waxy corn variety. Likewise, amylopectin ranged from 96 to 98 percent that equivalent to waxy corn. While the waxy parent, Kwi no.1 had 0.45 of tryptophan and 98 percent of amylopectin. The diallel cross was made by Griffing's method IV within each breeding method. The results showed that the best green weight of hybrids was the cross of As8 x As5 that gave 2,127 kg/rai and the dehusk weight was 1,260 kg/rai. As5 had a good general combining ability (GCA). Moreover, F1-hybrid of opaque-waxy corn had high tryptophan content as opaque-2 and high amylopectin as waxy.