Interspecific Hybridization in Leucaena Bentham

Thirteen Leucaena species and subspecies were studied from 1982-1987. Their valid species status was previously determined from chromosome numbers, geographical distributions, ecology and morphology. Present studies include self-incompatibility, interspecific hybridization, and morphological analyses of FI interspecific hybrids. Self-incompatibility (SI) was tested by hand pollinating 184 flower heads (2/805 florets). Two tetraploid species (4x=104) were self-fertile of the three tetraploid and eight diploid species selfed. Selfed progenies of L. esculenta (2x=52) were discovered. L. retusa (2x=56) was weakly self-fertile. Possible selfed progenies of four other diploid species were grown. None of the species hybrids grown were self-compatible except those derived from mating self-compatible species. A refined emasculation technique helped in hand pollinating 1420 inter- and sub-specific crosses (22/193 florets)/ thereby testing 135 of the 156 (86.5 %) species combinations in a 13 x 13 diallel. The genus was largely interfertile as 55 of the 64 species combinations (64/135 or 47.4 %) producing viable-appearing seed were grown and verified. In vitro techniques were used to grow two species hybrids from semi-abortive seeds. With reciprocal crosses combined/ 73 of the possible 78 (93.6 %) combinations in the diallel were tested/ and 47 (64.4 %) produced viable-appearing seed. Fourteen species combinations (14/135 or 10.4 %) produced abortive seeds. Two tetraploid hybrids resulted from the mating of a diploid (2x=56) x tetraploid (4x=104) mating. These tetraploid hybrids probably resulted from the union of a normal pollen of a tetraploid species (n=52) with an unreduced egg of a diploid species (2n=56), resulting in novel 4x=108-chromosome species hybrids. Growth rates rates of 50 species hybrids were determined. The fastest mean growth rate was 4.3 m/yr by L. divecigifolia X L. pallida (4x=104). Seven hybrids had mean growth rates greater than 3 la/yr, and 23 hybrids had mean growth rates greater than 2 m/yr. Thirty hybrids had at least one tree which increased in height faster than 3 m/yr. The fastest growth rate of any tree was 6.2 m/yr by L. diversifolia x L. collinsii (2x=54). Psyllid resistance to Heteropsylla cubana Crawford in the interspecific FI hybrids was better than most L. leucocephala. Five hybrids had no observable damage from psyllids. One appeared to be heterotic for psyllid resistance, and one appeared to have poorer resistance than either parent. Glands were observed on pinnae rachises of L. esculenta leaves, and appear to be producing mucilage which was implicated in psyllid resistance. Forty-one species hybrids reached sexual maturity/ but 14 (34.1 %) failed to produce any viable seeds from open-pollination. Mean viable seed per pod production of the 27 hybrids setting pods was 37.4 %. Yellow and red floral color, gland shape and number per leaf, floral bract shape, and inflorescence diameter were useful markers for identifying species hybrids. All appeared to be inherited additively in the FI, and all appeared to exhibit dosage effects except for gland and bract shape. Red flower color was recessive to yellow in matings of yellow x red flowers. Numbers of leaflets per pinna and pinnae per leaf and leaflet lengths and widths in 50 interspecific hybrids and their parents were counted or measured. Parental and FI hybrid data for leaf characteristics were linearized when plotted as the natural log of the data. Dosage effects occurred in triploid hybrids. Most (148/200 or 74 %) predicted hybrid leaf traits were predicted within 20 % of actual hybrid measurements; predictability would have been higher if data were used only from healthy mature trees. Only L. retusa x L. collinsii had leaflets which were not intermediate in size between than of the parental species. Leaf trait analysis was helpful in determination of parents of an open-pollinated species hybrid. Meiotic chromosomes were studied in two species hybrids and one species. L. collinsii K450 had 28 II, L. retusa K280 X L. collinsii K450 had 4 II + 48 I and L. diversifolia ssp. trichandra K399 x L. collinsii had 26 II + 2 I

Wood Properties of Twenty Highly Ranked Radiata Pine Seed Production Parents Selected for Growth and Form

Twenty highly ranked radiata pine (Pinus radiata D. Don) seed production parent trees, grown under a commercial sawlog regime, were destructively assessed at rotation age (27 years) for wood quality traits significant to solid-wood and veneer products, including: juvenile-wood density, density variation, juvenile-wood spiral grain, compression wood, and appearance characteristics such as within-ring internal checking and resin pockets. Traits varied considerably among parents, which is reasonable since breeding efforts in New Zealand have, until recently, focused primarily on stem productivity and form. Parental information is useful for many wood properties owing to their high heritabilities in radiata pine (usually 50-80%); thus production forests established using advanced-generation genetic materials can also be expected to be variable in wood properties. Like other fastgrown pines, much of the radiata pine crop is juvenile wood, and an important challenge for tree improvement is to ensure that juvenile wood properties meet processor and end-user requirements