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In Vitro Dry Matter Digestibility, Leaf Anatomy, and Fiber Concentration of a Hybrid between C₃ and C₃–C₄ Panicum Species

Dep. of Agronomy, Univ. of Georgia, Athens, GA 30602;

D. E. Akin

Russell Res. Ctr., P.O. Box 5677, Athens, GA 30613.

^* Corresponding author.

The Panicum genus has C₃–C4 species with characteristics between those of C₃ and C₄ species, and digestibility of C₄ or C₃–C₄ species might be improved by hybridizing with more digestible C₃ plants. Leaves of greenhouse-grown. P. spathellosum Doell (C₃–C₄), P. boliviense Hack. (C₃), and their F₁ hybrid were evaluated for characteristics related to forage quality. Leaves were digested in rumen fluid to determinine in vitro dry matter digestion (IVDMD) and degradation of specific leaf tissues. The hybrid was intermedite and differed (P < 0.05) from its parents in leaf IVDMD with values of 642 g kg^–1 compared to 630 and 709 g kg^–1 for the C₃–C₄ and C₃ species, respectively. The hybrid was also intermediate (P < 0.05) to its parents in the percentage of sclerenchyma, lignified bundle tissue, phloem, abaxial epidermis, and mesophyll. The hybrid had 18.8% of its leaf cross-section as parenchyma bundle sheath compared 15.0% for P. boliviense and 16.5% for P. spathellosum. Neutral detergent fiber was 583 g kg^–1 for the hybrid compared to 511 and 568 g kg^–1 for the C₃ and C₃–C₄ parents, respectively. Acid detergent fiber was 61 g kg^–1 greater than for the C₃ parent. The hybrid showed greater loss of mesophyall and epidermal tissues than P. spathellosum in top leaves, but only for abaxial epidermis in bottom leaves. Hybridization affected leaf anatomy and fiber characteristics related to digestibility. However, degradation of specific tissues did not follow consistent trends, suggesting that intrinsic factors within cell walls can override anatomical changes.

Key Words: Plant breeding • Forage quality • Fiber digestibility • Tropical grasses

Received for publication May 21, 1987.