Kenneth W. Mudge

Vegetative propagation of Inga feuillei from shoot cuttings and air layering

Cuttage and air layering were evaluated as means of vegetative propagation of the tropical woody tree, Inga feuillei. Effects of moisture management systems, leafiness, auxin application, and stem diameter on rooting of semihardwood cuttings were investigated. Cuttings were taken from 2-year-old seed-propagated, greenhouse-grown stock plants. Compound leaves were either reduced in area or removed entirely before auxin pretreatment with 0, 0.3, or 0.8% indolebutyric acid (IBA) followed by sticking under mist or in a polyethylene enclosure. Leafless cuttings did not root regardless of moisture management system or auxin pretreatment, whereas 55% rooting of leafy cuttings was observed. Leafy cuttings rooted significantly better under mist than in a polyethylene enclosure. Auxin treatment at the higher level increased rooting percentage approximately two fold for larger diameter cuttings (8.1 to 20 mm), but had no effect on the smaller cuttings (2 to 8 mm), and resulted in an approximately three fold increase in the number of roots/rooted cutting for both stem diameter classes. Auxin treatment did not affect rooting percentage of leafy softwood cuttings under fog, however it did increase the number of roots per rooted cutting. One hundred percent of air layered shoots rooted within 5 weeks with or without auxin pretreatment, and all rooted layers survived transplanting to soil. Possible implications of this research on agroforestry, selection, genetic improvement, and conservation are discussed.

Factors affecting the establishment and maintenance of 'Titan' red raspberry root organ cultures

Root organ cultures of red raspberry (Rubus ideaus cv. Titan) were established from two cm long terminal segments of adventitious roots induced in vitro on micropropagated shoot cultures. Growth of root organ cultures was almost entirely by initiation and elongation of lateral roots rather than by terminal elongation from the apical meristem of the original root explants. Indolebutyric acid (IBA) was required for lateral root initiation and elongation. The optimal IBA concentration for lateral root initiation decreased from 0.5 to 0.1 mg/L from the first to the fifth passage in culture. Two cm root explants initiated more lateral roots per unit length than four cm explants. Liquid Andersons medium was superior to other basal nutrient and vitamin formulations tested. Root growth in liquid culture was stimulated by aeration. Root organ cultures also grew on media solidified with gelrite or agar. A rapid transfer technique was developed for subculturing these which involved cutting and transferring 1 cm discs of roots and underlying medium. Adventitious bud formation occurred spontaneously, but sporadically in liquid cultures, and was not influenced by cytokinin, auxin (spat) light, or chilling.

Gypsum effects on plant growth, nutrients, ginsenosides, and their relationship in American ginseng

Wild American ginseng is typically found in the shade of deciduous forests, in slightly acidic soils with a relatively high Ca content. Wood-cultivated ginseng is often grown using forest farming agroforestry systems under similar conditions. Supplementing Ca by soil incorporation of gypsum (CaSO4·2H2O) is often recommended for wood-cultivated ginseng. The objective of this study was to determine the effects of gypsum application on ginseng growth, tissue nutrients, and ginsenoside contents in American ginseng. Three-year-old rootlets were grown for 120 days with 0, 2, 4, 8, or 16 Mt·ha−1 gypsum in greenhouse containers. Gypsum application reduced the soil pH slightly and elevated soil electrical conductivity (EC) and available soil Ca and S contents. While the Ca content in the ginseng increased with increasing levels of applied gypsum, shoot and root growth decreased. Root fresh weight prior to transplanting primarily affected the contents of ginsenoside Re, Rb1, Rc, and Rd and total ginsenosides. Gypsum treatment increased ginsenoside Rb1, Rc, and Rd and total ginsenoside contents. Furthermore, soil Ca, Mn, Cu, and Al contents positively correlated with total ginsenoside, but Mg was negatively correlated. HPLC analysis of root ginsenosides revealed that, although the concentrations of ginsenoside Rb1, Rc, and Rd increased with gypsum treatment, the contents of total ginsenosides were reduced. Changes in concentration may result from reduced root growth. Therefore, the results suggest that excess gypsum application (over 2 Mt·ha−1) is not beneficial for American ginseng production due to reduced plant growth.

Water deficit affects plant and soil water status, plant growth, and ginsenoside contents in American ginseng

American ginseng (Panax quinquefolius L.) produces pharmacologically active secondary compounds known as ginsenosides which have been shown to be influenced by both genetic and environmental factors. In a greenhouse experiment, effects of water deficit on ginseng plant growth, predawn leaf water potential (ΨLeaf), soil water potential (ΨSoil), leaf abscisic acid (ABA) concentration, and root ginsenoside contents as well as photosynthesis-related physiological responses were studied. Three-year-old seedlings, grown in 200 mL volume of plastic pots, were well watered for 45 days prior to the initiation of water deficit treatments. Plants in the water deficit treatments were irrigated every 10 or 20 days for the mild and severe water deficit treatments, respectively, while the control plants were watered every 4 days. The experiment was terminated after 15, 6, and 3 dry down cycles (60 days) for the control, mild, and severe water deficit treatments, respectively. As water deficit progressed, both ΨSoil and ΨLeaf decreased, but foliar ABA concentration increased. Other physiological responses to water deficit, including transpiration rate, stomatal conductance, and CO2 assimilation rate, were decreased. Water deficit decreased root growth, but unaffected shoot growth. Foliar chlorophyll content was also decreased in the water deficit treatments. The contents of individual ginsenosides Re, Rb1, Rc and Rd, and total ginsenosides were increased in the storage roots of water deficit-treated plants as compared with well-watered controls. Rootlet fresh weight before transplanting (RFWBT) as a covariate had a significant effect on the contents of ginsenoside Rb1, Rc, and Rb2. Overall, the results indicate that water deficit could contribute not only to reducing plant performance but also increasing the levels of ABA and certain ginsenoisdes.

Clonal propagation of Leucaena by single bud splice grafting with a new grafting tool, and by modified veneer crown grafting

A simple tool called the graft guide, and its use with a new grafting technique called the single-bud splice (SBS) graft is described. The graft guide assures precise complementary rootstock and scion cuts, and thus ensures good cambial contact necessary for graft union formation. The use of this tool to graft small (3–15 mm) vegetative shoots of Leucaena species and hybrids is illustrated. An overall grafting success rate of 72% was achieved using this technique for several leucaenas. An additional modified veneer grafting technique for use when rootstock is larger in diameter than the scion, achieved 73% success. Graft compatibility results from 961 grafts between scions of 15 Leucaena species and three interspecific hybrids, and rootstocks of two species are presented. Of the 48 scion/rootstock combinations attempted, 43 (90%) were successful.

Open-pollinated, interspecific F1 hybrid seed orchards of Leucaena : I. Rootstock effects

Seed orchards of Leucaena were established at two experimental sites in Hawaii to produce either triploid or tetraploid interspecific hybrid seed by interplanting clonal self incompatible diploid (L. diversifolia, L. esculenta) or tetraploid (L. pallida) species with self- compatible L. leucocephala lines and the F1 hybrid of L. diversifolia (2n = 4x) × L. leucocephala. The seed parents were grafted onto three seedling rootstocks (L. diversifolia (2n = 4x), shrubby L. leucocephala, and giant L. leucocephala) to compare rootstock effects on scion growth. This paper reports on the effects of rootstock on scion growth during the first year based on total truck cross sectional area, height growth, and crown habit. In the triploid seed orchard, rootstock significantly affected the growth of four of the six clones, while in the tetraploid orchard the growth of two of the five clones was significantly affected by rootstock. Crown habit was independent of rootstock. Our study suggests that rootstock effects depend on the specific scion and rootstock combination, and site.

Open-pollinated, interspecific F1 hybrid seed orchards of Leucaena II. Analysis of seedlings

Seed produced on a single clone of a self-incompatible Leucaena species interplanted with cross compatible pollen donors of another species should theoretically be interspecific hybrid seed. This paper reports on the parentage of seed produced on two clones (K804, K953) of L. pallida produced in two interspecific seed orchards during the first year of growth. Grafting was used to propagate the two L. pallida clones and the interplanted pollen donors including L. leucocephala (K420, K481, K636) and the F1 hybrid KX3 (L. diversifolia K156 × L. leucocephala K636). Seed was produced on L. pallida K804 in one orchard, and on L. pallida K953 in the other orchard. Seeding leaf morphological characteristics including pinnule pairs per pinna, pinnule width and general appearance were used to determine parentage of seed produced on the L. pallida clones in each orchard. L. pallida K804 produced 81% interspecific hybrid seed while L. pallida K953 only produced 27% hybrid seed. These results suggest a breakdown of the gametophytic self-incompatibility mechanism in L. pallida, particularly in the K953 clone. The feasibility and possible improvement to this seed production system are discussed.