JC Schultz; UNIV GOTTINGEN; INST AGRON & PLANT BREEDING; GOTTINGEN; GERMANY; D-3400 BCIn vitro propagated oil palms have to be adapted to natural conditions. In the weaning stage the period after micropropagation under sterile conditions and before transplanting to the nursery, plants are subjected to severe environmental stress, due to poor root-shoot growth and reduced cuticular wax formation. The percentage of mortality is about 30% during this phase and further 10% of the plantlets do not survive transfer to the prenursery. The use of (vesicular-) arbuscular mycorrhizal fungi (VAM) can be specially beneficial to perennial crops. The nim of this study was to investigate the effect of (VAM) inoculation on the survival of micropropagated oil palm plantlets during the weaning stage. Two experiments were conducted in Bogor and Medan, Indonesia. The plantlets were inoculated with different mycorrhizal fungi, the survival rates were determined twice a week. The plants were harvested after three months. In both experiments inoculation of (VAM) fungi had a significant positive effect. In the mentioned sensitive stage the survival( rates of the micropropagated oil palm clones were increased from 70% to 90-95%.
JB Fisher; Fairchild Trop Garden, 11935 Old Cutler Rd, Miami, FL 33156 USA; Fairchild Trop Garden; 11935 Old Cutler Rd; Miami; FL; USA; 33156Serenoa repens (Bartr.) Small is a palm native to the southeastern USA. It is a common understory plant in pine communities on both acid sands and alkaline limestone. Roots have only primary growth and range in thickness from 8.0 mm (first order roots from the stem) to 0.8-2.9 mm (ultimate roots of third to fifth order). The thickest roots occur at soil depths > 20 cm; fine roots (< 1.2 mm) occur at all depths (1-60 cm). Some second and third order roots are negatively geotropic and grow up to the mineral soil surface. The epidermis of all roots has a thick, eventually lignified outer wall. Except for the thinnest, all roots have a single-layered, thick-walled exodermis, which is first suberized and later lignified. Root hairs are never present. A hypodermis composed of several layers of lignified cells (up to 8-cells-thick) is next to the exodermis and forms the outer cortex. Radial series of thin walled and slightly lignified cells sporadically occur in the outer cortex of the thinnest roots, but there are no passage cells in the exodermis, which is continuous. The remaining inner cortex is composed of unlignified parenchyma with air canals and a completely lignosuberized endodermis in old roots. Passage cells were seen the the endodermis of the some of the thinnest roots. Arbuscular mycorrhizal (AM) fungi occur in the outer one-third of the cortical parenchyma adjacent to the hypodermis. Fungal coils, arbuscules and vesicles are found most frequently in the thinnest roots, but also occur sporadically in all root orders. Cells a few mm from the apical meristem are sometimes colonized. At sites of appressoria, coils of AM hyphae occur within an epidermal cell and exodermal and hypodermal cells beneath. Intercellular hyphae with intracellular branch arbuscules (Arum-type) are common in the inner cortex. There is evidence of a dieback of the highest order roots during the winter dry season. Profiles of soil and roots have the highest density of AM spores in the surface 10 cm layer. Total AM spore density ranged from 130 to 1100 spores per 50 g soil in different samples. Glomus spp. dominated followed by Gigaspora spp. The findings are related to a more general understanding of growth and AM colonization in long-lived roots of tropical woody monocotyledons. Palm roots, in particular, are slow growing and are protected by massive hypodermal layers.
Oihabi A, Fac Sci Semlalia, Lab Physiol Vegetale, BP S-15, Marrakech, Morocco.Tolerance of mycorrhized clover (Trifolium alexandrinum L.) to drought depends on the arbuscular mycorrhizal fungi associated to the host plant. Five arbuscular mycorrhizal fungi isolates were collected from five Moroccan date palm grove's soils and were investigated for their ability to improve the plant tolerance to water deficit stress. Applying a constraint of 30% field capacity reduces severely the mycorrhizal rate in the root cortex of most of the tested isolates. Fungi collected from Aoufous date palm grove were less affected by the drought than the other strains, such as Glomus and Sclerocystis isolated from Agdz soil. The effect of micorrhization on the biomass production occurred for the isolate of Aoufous and Glomus mosseae (reference strain obtained from INRA Dijon. France). These fungi allowed the plants to maintain its water content. water potential and its leaves transpiration at high levels compared to the non inoculated plants. The values of stomata resistance and the saturation deficit in water remained lower for mycorrhized plants than non-mycorrhized. Ones further more, the isolate of Aoufous and Glomus mosseae were the most virulent colonizing the host plants regard less of the level of water deficit in the soil. Autochthon isolates originating Aoufous date palm grove was as efficient as Glomus mosseae.
AM Moawad; INST AGRON TROP; GRISEBACHSTR 6; GOTTINGEN; GERMANY; D-37077 BCAlthough the presence of the obligate symbiotic(vesicular-) arbuscular mycorrhizal (VAM) fungi in nature has been known for many decades, their potential benefits have been recognized only relatively recently. In natural ecosystems the roots of most higher plants are inhabited by typical structures of these beneficial fungi which play a very important role in host plant nutrition, especially with nutrients of low mobility in the soil solution such as phosphorus, With the renewed interest of the-past years in sustainable agriculture, VAM has gained in popularity due to the high expectations in capturing the potential benefits from VAM in improving crop production. Other benefits of the symbiosis with VAM include increased plant resistance to disease and tolerance to salinity and drought and enhanced biological nitrogen fixation (BNF) by leguminous crops and trees. Furthermore, mycorrhiza improves the efficiency of water-use by plants. Over the last years it has been demonstrated that inoculation with VAM as a biological measure can result in growth enhancement of a wide range of micropropagated plants especially of those difficult-to-root species. There are some evidences that YAM inoculation could be beneficial in increasing the survival rates of micropropagated oil palm. The general benefits of VAM for the growth of crops in natural and micropropagation systems are discussed.
Address:UNIV HAWAII MANOA,COLL TROP AGR & HUMAN RESOURCES,DEPT HORT,HONOLULU,HI 96822
INST POLITECN NACL,ESCUELA NACL CIENCIAS BIOL,MEXICO CITY 02800,DF,MEXICO.Tecoman, in the Mexican state of Colima, had the world's greatest production of lime Citrus aurantifolia Swingle. Typical farming systems in the area include: (a) high-input monoculture, (b) a high-input system in which lime trees grow together with coconut palms, (c) a low-input system called ''Family Farms'' or ''Family Gardens''. In the Family Gardens, cultural practices are minimal and other fruit trees (about 16 species) coexist with the lime trees. This traditional minimal input system makes use of locally available resources and they are structurally very diverse. Arbuscular mycorrhizae may be crucial for sustainable production in Family Gardens. Root colonization and spore populations of fungi were scored at 2-week intervals in the three agroecosystems during a 6-month period. First samples were taken after the application of chemical fertilizer and irrigation in the high-input systems. Root colonization of lime was much higher and consistent in the low-input plots than in conventionally farmed plots, with colonization levels of 50-62% that remained the same throughout the sampling time; the high-input systems showed a high variation and lower level of colonization, 36% and 27% in associated and monoculture systems, respectively. Spore abundance was higher in the high-input systems but showed constant variation. The results suggest a strong effect of agroecosystem on mycorrhizal colonization of lime roots.
CLEMENT CR, UNIV HAWAII MANOA,COLL TROP AGR & HUMAN RESOURCES,HONOLULU,HI 96822
Two experiments were undertaken to determine the degree of mycorrhizal dependency of pejibaye (Bactris gasipaes, Palmae) seedling progenies from two Amazonian (Pampa Hermosa; Putumayo) and one Central American (Guatuso) land races. Plants were grown in subsurface samples of either an Oxisol (the Amazonian progenies) or an Ultisol, with or without inoculation with the vesicular-arbuscular mycorrhizae fungus (VAMF) Glomus aggregatum, at three concentrations of soil solution phosphorous (P). VAMF inoculation enhanced leaf phosphorus (P) concentration and dry matter accumulation at the intermediate soil P concentration in all progenies. Dry matter accumulation was enhanced by 17%, 54%, and 64% in the Pampa Hermosa, Putumayo, and Guatuso progenies, respectively. They are therefore classified as being marginally (Pampa Hermosa) or highly dependent. This infra-specific genetic variation with respect to mycorrhizal dependency merits further study for possible exploitation in plant improvement for sustainable agriculture.