Variation and Covariation in Stover Digestibility Traits in Diallel Crosses of Maize

Abstract

In the cooler regions of the world, the area under forage maize (Zea mays L.) production has increased, and breeding for digestibility has gained importance. This study was conducted on digestibility traits of stover in maize forage, to determine variation, as analyzed by the combining‐ability approach, and correlation coefficients (r) in these traits and r between these and dry matter (DM) yield traits. Diallel crosses among 12 inbred lines were evaluated at silage and grain harvests for 2 yr at two agro‐climatically diverse locations in West Germany. Stover samples were analyzed for in vitro digestible organic matter (IVDOM), neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) using laboratory and near infrared reflectance spectroscopy (NIKS) methods. Mean squares due to general (GCA) and specific combining ability (SCA) and their interactions with environments (GCA ✕ E, SCA ✕ E) were, for the most part, significant. At silage harvest, GCA was the most important source of variation in all traits, followed by SCA ✕ E interactions. At grain harvest, GCA and SCA ✕ E for IVDOM and ADL and SCA ✕ E for NDF and ADF accounted for larger variability than SCA and GCA ✕ E. The genetic ratio indicating the relative importance of GCA vs. SCA was > 0.81 in all cases, except that it ranged from 0.40 to 0.58 for NDF and ADF at grain harvest. The IVDOM had negative r with NDF, ADF, and ADL, and r values were stronger at silage harvest; IVDOM was not correlated with stover DM yield, and had negative r with ear DM yield. The results showed significant genotypic variation for several traits, with GCA the most important source of variation for most traits, and showed that selection for digestibility should preferably be made at the ensiling stage.

Relevant traits, genetic variation and breeding strategies in early silage maize

“…Numerous works proved large genetic variations in the in-vitro digestibility of maize, either for whole plants or cell walls parts (eg, Gallais et al, 1976;Deinum and Bakker, 1981;Vattikonda and Hunter, 1982;Deinum et al, 1984;Deinum and Struik, 1985;Deinum, 1988;Dhillon et al, 1990b; Dolstra and Medema, 1990;Geiger et al, 1992;Hunt et al, 1992;Seitz et al, 1992;Dardenne et al, 1993;Dolstra et al, 1993;Wolf et al, 1993;Barrière et al, 1993a;Coors et al, 1994;Lundvall et al, 1994;Argillier et al, 1995). In early lines, according to Dolstra and Medema (1990) (Argillier et al, 1995) When considering the digestibility of whole plants, as well as stover, stalks or cell-walls, GCA effects for in-vitro values of digestibility were often preponderant over SCA effects.…”

Genetic variation and selection criterion for digestibility traits of forage maize

“…The high digestibility of some brown-midrib mutants was the first indication of a great genotypic variation in the digestibility of maize plants (see review Barriere & Argillier, 1993) . Since then, genotypic variations for in vivo, in sacco, and in vitro digestibility of the dry matter (DM) or organic matter (OM) of the whole plant or of the stover part have been highlighted among normal maize hybrids (Deinum & Bakker, 1981 ;Vattikonda & Hunter, 1983 ;Deinum & Struik, 1985 ;Deinum, 1988 ;Dhillon et al ., 1990 ;Dolstra & Medema, 1990 ; Barriere et al ., 1992 ;Dardenne et al ., 1993 ;Flachowsky et al ., 1993 ;Wolf et al ., 1993) . It can be suggested that differences in forage maize feeding value are expressed best as differences in animal performance (e .g ., milk production or daily gain) .…”

Genetic improvement of cell-wall digestibility in forage maize (Zea mays L.). I. Performance of inbred lines and related hybrids

“…All entries of the various trials were harvested on the same day and not separately at a more precisely determined growing stage as has been done, for example, in related research in Germany Dhillon et al ., 1990 ;Zimmer et al ., 1990 ;Gurrath, 1991) . This is allowed since in these late developmental stages stalk-dcw% is a stable trait which is not affected by either environmental or developmental variation (Dolstra & Me- However, our data show the latter to be superior owing to a higher broad-sense heritability .…”