Laboratory Evaluation of Quality in Subtropical Grasses. III. Genetic Variation among Digitaria Species in In Vitro Digestion and its Relationship to Plant Morphology1
- M. A. Klock,
- S. C. Schank and
- J. E. Moore2
In vitro organic matter digestion procedures (IVOMD) were used to evaluate a wide range of Digitaria spp. (digitgrass) breeding lines at three stages of maturity, across 11 field replications of one genotype, and as full-sib families evaluated at two locations and with two fertilizer treatments. Observations were made on the effect of flowering culms and stem microanatomy on digestibility. Information on the variation in digestibility among digitgrass hybrids and factors which may affect digestibility would be useful in selecting promising genotypes early in a breeding program.
At 3, 5 and 7-week regrowth, IVOMD ranged respectively from 69.8 to 77.7, 56.6 to 68.4 and 50.7 to 64.0% on different lines. Lines lower in digestion at 3-week re-growth were lower at 5 and 7 weeks, and lines initially higher in digestion usually remained higher at all three harvests. Eleven field replications of a clonally propagated genotype did not differ significantly, nor did three laboratory replications per sample. Significant differences in IVOMD were detected not only among hybrid families, but also within some of the families (among full sibs).
A factorial analysis was performed on IVOMD data on five hybrid families. Significant differences in digestion among genotypes, families, levels of fertilization, and location were observed. The genetic portion constituted the greatest single component of the total variance. The range in IVOMD was 53.9 to 76.3% among genotypes and 57.8 to 73.1% among families. Genotype IVOMD correlated directly with family mean for each harvest. A highly significant negative correlation (r = −0.81) was found between percent IVOMD and percent seed stalks. Micro-scopic examination revealed that genotypes with low digestion showed more evidence of secondary cell wall thickening in nodal regions of the stem than did those genotypes with high digestion.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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