Selection of Robinia pseudoacacia var. monophylla for increased feeding value in the Mediterranean environment

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1 Selection of Robinia pseudoacacia var. monophylla for increased feeding value in the Mediterranean environment O. DINI PAPANASTASI AND T.G. PAPACHRISTOU National Agricultural Research Foundation, Forest Research Institute, GR Vassilika Thessaloniki, Greece Summary Black locust (Robinia pseudoacacia L.) is a leguminous tree cut back to produce fodder of high feeding value for domestic and wild animals. With appropriate selection programmes this can be further improved and a trial was carried out in order to evaluate clones and open-pollinated families of black locust for CP and NDF contents in summer (July) and autumn (October). The following material was included in the test: rooted cuttings of twelve trees selected in northern Greece within seven open-pollinated families of Robinia pseudoacacia var. monophylla (or unifolia), rooted cuttings of a single very productive tree of the same variety, rooted cuttings of the clone-variety umbraculifera, seedlings of the seven open-pollinated families, seedlings from a bulked mixture of seeds representing the mean population and seedlings of common black locust. It was found that seasonal changes in CP and NDF values were much lower in clones than in families. CP content was higher in clones than in families during October. Two of the most promising clones of Robinia pseudoacacia var. monophylla with an increased feeding value in autumn should be further tested before they are introduced into livestock production systems of the Mediterranean environment. Keywords: browse, clone selection, fodder plants, nutritive value. Introduction Black locust (Robinia pseudoacacia L.) is a nitrogen-fixing leguminous tree, native to southeastern North America, which has become naturalised in the temperate regions of Europe and Asia. It has several botanical varieties including one with few leaflets per compound leaf (monophylla or unifolia) and an umbrella-shaped variety (umbraculifera) (Keresztesi, 1988). It is a multi-purpose species suitable for wood production, fuel, land reclamation, beekeeping and forage (Barrett et al., 1990). Its use for forage is becoming a prominent practice in several parts of the world due to its high feeding value for domestic and wild animals. The main characteristics of black locust are its relatively high CP and low lignin contents, making it a comparable feed to alfalfa (Medicago sativa, L.) (Barrett et al., 1990). For this reason, it is an important fodder for ruminants during the long and dry summer Grasslands and Woody Plants in Europe 51

2 O. Dini Papanastasi and T.G. Papachristou period of the Mediterranean environment when herbaceous species are dormant and other woody species are less nutritious (Papachristou & Papanastasis, 1994). As in all plant species, however, CP in black locust decreases and lignin increases as the growing season progresses thus resulting in reduced digestibility of its foliage towards the end of the summer beginning of autumn (Khosla et al., 1992; Papachristou & Papanastasis, 1994). In this paper, the results are reported of a breeding programme aimed at selecting cultivars which maintain a high CP content in their foliage for a longer period in the summer and therefore filling up the seasonal nutritional gap of the Mediterranean environment more efficiently. Materials and methods The experiment was carried out on the Forest Research Institute farm, 20 km NE of the city of Thessaloniki, northern Greece (40º 35 north latitude and 22º 58 east longitude). Soils of the study area are sandy loams, derived from deposits of the tertiary period, fairly deep (1-2 m) and alkaline (ph 7.7). Climate is semi-arid Mediterranean with 416 mm longterm mean annual rainfall, 31.7ºC mean maximum air temperature in July and 0.2ºC mean minimum in January (Tsiontsis, 1995). The trial was carried out in order to test various selections (clones) and open-pollinated families of black locust for CP and NDF contents at two stages of maturity. The following material was included in the test: (A) rooted cuttings of twelve trees selected within seven open-pollinated families of R. pseudoacacia var. monophylla in northern Greece, (B) rooted cuttings of a single very productive tree of the same variety (Strymon selection), (C) rooted cuttings of the clone - variety umbraculifera, (D) seedlings of the seven open pollinated families, (E) seedlings from a bulked mixture of seeds representing the mean population and (F) seedlings of common black locust. The selection criteria for the twelve trees were growth performance and production of a dense, rich and fresh foliage in early November (Dini-Papanastasi, 1997). All plants both rooted cuttings and seedlings were one year old and planted at a spacing of 2.5 m x 2.5 m (30 rows of 14 plants each) on April 21, 1994, with border plants all around the trial. The clones and families were represented by varying numbers of ramets and seedlings, respectively, and for this reason a completely randomised design with unequal samples was employed (Fasoulas, 1979). The nutritional quality of the plants was determined at two stages of maturity in 1995: mature leaves at the end of July and senescent leaves at the end of October. At least three forage samples, consisting of compound leaves were collected by hand from representative plants of each one of the plant categories (A-F). As far as possible the sample plants used were common for both sampling times. Samples were analyzed for nitrogen (N) using the macro-kjeldahl procedure (AOAC, 1990) and crude protein (CP) calculated as Nx6.25. Neutral detergent fibre (NDF) was assessed by the Goering & Van Soest method (1970). The t-test was used to detect differences of CP and NDF in clones and families between the two-maturity stages and also differences of CP and NDF in the two maturity stages between clones and families. CP and NDF data were also subjected to one-way analysis of variance to compare all clones and families; if differences were significant, the means were compared with the Duncan test at the 0.05 level. 52 Grassland Science in Europe

3 Selection of Robinia pseudoacacia var. monophylla for increased feeding value in the Mediterranean environment Results and discussion As expected, CP decreased and NDF increased from July to October but CP of clones decreased less (4%) than of families (11%) between the two periods, only the latter reduction being significant (Table 1). Similarly, NDF increased less in the clones (8%) than in families (18%), both increases being significant. These findings are in agreement with those reported by Papachristou & Papanastasis (1994) indicating the potential of Robinia as a source of nutrients throughout its growing period. Table 1. Comparison between crude protein content (DM basis, g kg -1 ) and neutral detergent fibre (NDF; DM basis, g kg -1 ) in July and October for Robinia clones and open-pollinated families with t-values. CP NDF July October t-value P July October t-value P Clones Families Statistically significant differences (P 0.05). Comparing maturity stages, CP and NDF values did not differ significantly between clones and families in July (Table 2). In October, however, there were significant differences between clones and families for CP content, clones being 8% higher. There were no significant differences for NDF values between the two groups of improved material. Table 2. Comparison between Robinia clones and open-pollinated families for crude protein content (DM basis, g kg -1 ) and neutral detergent fibre (NDF; DM basis, g kg -1 ) at two maturity stages (July and October) with t-values. July October Clones Families t-value P Clones Families t-value P CP NDF Statistically significant differences (P 0.05). Table 3 shows the CP and NDF values of the individual clones and families. CP ranged from to g kg -1 and NDF from to g kg -1 in July, with no significant differences. In October, the variation among the various selections was much higher and resulted in significant differences with CP values ranging from 140 to 206 g kg -1 and NDF values from to g kg -1. The Robinia browse in both periods had higher CP levels than those suggested for goat and sheep maintenance (63 g for goats, LW: 40 kg, NRC, Grasslands and Woody Plants in Europe 53

4 O. Dini Papanastasi and T.G. Papachristou 1981; 90 g for sheep, LW: 50 kg, NRC, 1985). This protein is of high digestibility and therefore available to animals (Papachristou, 1999). Table 3. Crude protein content (CP; DM basis, g kg -1 ) and neutral detergent fibre (NDF; DM basis, g kg -1 ) of 14 Robinia clones and 9 open-pollinated families at two stages of maturity (July and October). July October Plant categories CP NDF CP NDF Clones R. p. var. monophylla (12 selected trees) 1. A-8A(4) 178.6a a 157.8bc 348.1bcd 2. A-8A(7) 185.9a 312.1a 158.1bc 300.2d 3. A-8A(9) 166.3a 305.1a 186.8ab 361.8bcd 4. B-2B(8) 167.4a 297.5a C-2B(13) 184.5a 327.0a 167.3abc 319.1cd 6. A-2B(15) 174.1a 287.5a 149.3c 308.2d 7. A-A(7) 179.8a 296.0a 163.0bc 320.7cd 8. B-A(13) 171.3a 369.5a 206.0a 282.0d 9. A-7B(6) 173.2a 316.4a 162.4bc 366.8abcd 10. A-B(3) 164.0a 322.4a 179.2abc 349.6bcd 11. B-3A(7) 182.7a 308.9a B-6A(8) 173.1a 300.4a 180.9abc 278.9d (B) R. p. var. monophylla 172.4a 332.1a 159.1bc 398.1ab (Strymon selection) (C) R. p. var. umbraculifera 181.2a 360.9a 165.2abc 392.7abc Open pollinated families (D) R. p. var. monophylla (7 families) 1. 8A a 289.4a 144.5c 354.7bcd 2. 2B a 314.4a 204.8a 405.1ab 3. A a 286.5a 147.3c 293.8d 4. 7B a 298.8a 159.0bc 322.8cd 5. B a 308.7a 164.3bc 402.5ab 6. 3A a 311.4a 145.5c 442.7a 7. 6A a 339.0a 160.2bc 406.0ab (E) C 0 mean population 172.1a 322.9a 141.7c 300.0d (F) R. pseudoacacia (common) 175.7a 328.7a 140.0c 384.6abc 1 Means in the same column with different letter are significantly different (P 0.05). 54 Grassland Science in Europe

5 Selection of Robinia pseudoacacia var. monophylla for increased feeding value in the Mediterranean environment The results suggest that individual clones can be selected for increased CP and decreased NDF levels in October for use in animal production systems. Table 3 shows that clone B-A(13) has a very high CP level and a relatively low NDF content (below the clones mean) and therefore it can be a priority candidate for selection. Another promising clone is B-6A(8). Both clones were also had the highest CP contents during October 1994 (Dini- Papanastasi, 1997). Further testing in wider environmental conditions for several years is required to confirm their value for animal feeding before they are introduced into livestock production systems. Conclusions 1. Seasonal changes in CP and NDF values were much lower in clones than in families. 2. CP content was higher in clones than in families during October. 3. Clones B-A(13) and B-6A(8) of R. pseudoacacia var. monophylla were found to be the most promising ones for increased feeding value in early autumn and are recommended for further testing before they are introduced into livestock production systems of the Mediterranean environment. Acknowledgements This research was financed by the Greek Ministry of Agriculture and by the CAMAR programme of the European Commission ( CT ). References AOAC, Official methods of Analysis, 15 th ed Association of Official Analytical Chemists, 746 pp. Washington, DC. Barrett R.P., T. Mebrahtu & J.W. Hanover, Black locust: A multi-purpose tree species for temperate climates. In: Advances in New Crops. J. Janick & J.E. Simon (eds.). pp Timber Press, Portland, OR. Dini - Papanastasi, O., Inheritance of traits of Robinia pseudoacacia L. and their relation with biomass production. PhD Thesis, 152 pp. Aristotle University of Thessaloniki, Greece. Fasoulas, A., Elements of Experimental Statistics. 255 pp. Thessaloniki, Greece. Goering, H.K. & P.J. Van Soest, Forage Fiber Analysis. ARS, USDA Agricultural Handbook No 379, 20 pp. Keresztesi, B., The Black Locust. Forestry Monograph-Series of the Agricultural Science Department of the Hungarian Academy of Science. B. Keresztesi (ed.). 197 pp. Budapest. Khosla, P.K., O.P. Toky, R.P. Bisht & S. Hamidullah, Leaf dynamics and protein content of six important fodder trees of the Western Himalayas. Agroforestry Systems, 19: NRC, Nutrient Requirements of Goats: Angora, Dairy and Meat Goats in Temperate and Tropical Countries. No pp. National Academy Press, Washington, DC. Grasslands and Woody Plants in Europe 55

6 O. Dini Papanastasi and T.G. Papachristou NRC, Nutrient Requirements of Domestic Animals. No 5. Nutrient Requirements of Sheep. 99 pp. National Academy of Sciences. National Research Council, Washington, DC. Papachristou, T.G., Assessing the value of black locust (Robinia pseudoacacia L.) browse for animal feeding. In: Grasslands and Woody Plants in Europe. International Occasional Symposium of the European Grassland Federation, Thessaloniki, Greece, May, 1999 (in this volume). Papachristou, T.G. & V.P. Papanastasis, Forage value of Mediterranean deciduous woody fodder species and its implication to management of silvo-pastoral systems for goats. Agroforestry Systems, 27: Tsiontsis, A., Meteorological data of the Forest Meteorological Stations of Northern Greece. Forest Research Institute Bulletin. Thessaloniki, Greece. 56 Grassland Science in Europe