Interspecific hybrids of Leucaena spp. (Ipilipil) for timber and fodder
2001
Brewbaker, J.L. | Shi, X. (University of Hawaii(Hawaii). Dept. of tropical Plant and Soil Science)
Interspecific hybridization in the genus Leucaena has involved 15 of the 22 recognized species, largely through research of former UH [Univ. of Hawaii] students. Among appproximately 200 crosses, approximately 80 have produced hybrid trees now growing in Hawaii. Species with no apparent geographic or botanical relationship often cross easily and exhibit remarkable heterosis. Chromosome numbers of the leucaenas include 2n=52, 56, 104 and 112, thus the hybrids and their progenies range widely in numbers and phenotype. Two of the outstanding interspecific hybrids have L. leucocephala (2n=104) as one parent. This species is represented generously in the flora of Philippines ("ipilipil"), Hawaii ("koa haole"), India ("Kubabul") and many other countries, where it occurs as a single self-pollinated genotype. This "common leucaena" is shrubby, seedy and weedy. However, arboreal varieties of this species from Mexico and Central America produce outstanding lumber-quality hybrids with L. esculenta (2n=52). Such hybrids are very rapid in wood growth, harvestable for timber in 8 to 12 years. They are also attractive ecologically since they are triploids that are seedless due to male sterility. Cloning methods have been refined in Hawaii, under support of Shell Forestry International, that permit advanced yield trials and lumber quality evaluations of clones like K1000. Outstanding forage-quality hybrids also result from the cross of arboreal cultivars like K636 of L. leucocephala with L. pallida (2n=104). These hybrids, designated `Kx2', are psyllid-tolerant and they have dominated fodder yield trials in Asia coordinated by Dr. Max Shelton of Univ. of Queensland. Research is ongoing to produce hybrid seed economically of these two valuable hybrids using self-incompatible clones of L. esculenta and L. pallida as female parents
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