Quantitative Trait Loci for Ruminal Degradability in opaque endosperm2 (o2) Maize.

Lebaka, Ntjapa G.; Coors, James G.; Shaver, Randy D.; Bertics, Sandy; Gutiérrez-Rojas, Andrés; Menz, Mónica; Betrán, Javier

Although opaque endosperm2 (o2) gene that alters protein composition of maize (Zea mays L.) endosperm improves dry matter degradability (DMD) in ruminants it is also associated with soft endosperm texture, low yield, and susceptibility to diseases and insects. To circumvent the undesirable traits, breeders developed high lysine modified endosperm genotypes called quality protein maize (QPM). The objectives of this study were to determine whether DMD is maintained in modified endosperm and to map major quantitative trait loci (QTLs) associated with ruminal in situ DMD (RDMD). Composited 1.5-g ground grain samples of 140 recombinant inbred lines (RILs) derived from the cross between o2 (B73o2) and QPM (CML161) lines were assayed for 14-h RDMD in three rumen-cannulated, midlactation Holstein cows (Bos taurus) and 0-h rapidly soluble dry matter (RSDM) in tepid water. The RILs were grown in Texas and were evaluated for RDMD at Madison, WI. Slowly degradable dry matter (SDDM = RDMD - RSDM) was estimated. Kernel opacity was positively correlated to 14-h RDMD (r = 0.68 and 0.71 in 2005 and 2006, respectively; P < 0.05). Quantitative trait loci for 14-h RDMD were detected on chromosomes 4, 5, 7, 9, and 10; QTLs for RSDM were detected on chromosomes 3, 5, 7, and 10; and QTLs for SDDM were detected on chromosomes 5, 6, and 9. Quantitative trait loci for 14-h RDMD and RSDM colocated on chromosomes 5, 7, and 10 might be genomic regions influencing 14-h RDMD mainly through kernel modification. Quantitative trait loci for 14-h RDMD and/or SDDM, on chromosomes 6 (SDDM) and 9 (colocated) where 14-h RDMD appears to be mediated through SDDM and most likely enzymatic RDMD, may be good candidates for improvement of RDMD.

CORN research; PLANT proteins; ENDOSPERM; GENOTYPES; PLANT chromosomes; LOCUS in plant genetics

Crop Science, 2013, Vol 53, Issue 2, p378

0011-183X

Academic Journal

10.2135/cropsci2011.12.0646