Periodic Existence of Mycorrhizal Fungi in Roots and Non-root Dissident Portions of Some Bulbous Plants

Arbuscular Mycorrhizae (AM) is mutually beneficial relationship amongst fungi and roots of the higher plants. Colonization of roots by mycorrhiza has been revealed to recover development and yield of numerous field crops including leguminous crops, cereals, vegetables and oil crops [1-5]. Mycorrhizal associations increase plant growth and productivity by increasing nutrient element uptake [6] and improving resistance to abiotic [7,8] and biotic [9] stress factors. Plants often benefit from the presence of mycorrhizal associates via a variety of mechanisms including improvement of soil structure, mobilization of essential minerals, enhancement of desiccation resistance, and protection from pathogens and herbivores [10]. Recently some workers have reported that AM also increase the crop tolerance against allelopathy and enhance crop growth under this stress [11,12].


Introduction
Arbuscular Mycorrhizae (AM) is mutually beneficial relationship amongst fungi and roots of the higher plants. Colonization of roots by mycorrhiza has been revealed to recover development and yield of numerous field crops including leguminous crops, cereals, vegetables and oil crops [1][2][3][4][5]. Mycorrhizal associations increase plant growth and productivity by increasing nutrient element uptake [6] and improving resistance to abiotic [7,8] and biotic [9] stress factors. Plants often benefit from the presence of mycorrhizal associates via a variety of mechanisms including improvement of soil structure, mobilization of essential minerals, enhancement of desiccation resistance, and protection from pathogens and herbivores [10]. Recently some workers have reported that AM also increase the crop tolerance against allelopathy and enhance crop growth under this stress [11,12].
Vesicular arbuscular mycorrhizae are of universal occurrence in roots of 95% of land plants [13,14]. However, during past few decades reports are available about the presence of AM in plant portions other than roots [15,16]. Since than a number of examples have been added to the literature with an emphasis on a much wider occurrence of these associations than reported ever before.
We had planned this study to further add to the information about AM proliferating in roots and non-root portions of some bulbous plants.

Materials and Methods
Sampling of root and non-root portions like scale leaves, dried decaying sheathing leaves on the bulbs of two test bulbous plants viz. Allium cepa, Amaryllis vittata and Zaphyranthes citrina. The sampling was done regularly from February to May. Specific sites (Sites name) were selected for sampling of plants. The root/bulb samples were dug up along with rhizospheric soil. Extreme care was taken to avoid the disturbance of root systems, adhering decayed and semi-decayed scale leaves and epidermis. The samples were brought back to the Lab. in polythene bags. Decaying scale like leaves and fine roots were gently peeled off with the help of forceps, while rest of the bulbous portion along with root system were dipped in a bucket of water for half an hour. The adhering soil was removed with the help of camel hairbrush while washing gently under the tap water. The root system of all samples, scales and other portions were cut up into 1 cm 2 pieces and then fixed in F.A.A. (Formaline: Acetic Acid : Alcohol in 5:5:90 ratio by volume) in properly labeled MacCartney bottles separately. The samples were cleared and stained for analysis of colonization of AM fungi using Phillips and Hayman procedure [15]. The roots were cleared in 10% KOH solution in an autoclave, placed in 0.1N HCl for 2-3 minutes for neutralization and then stained with trypan blue solution (0.05% in lactophenole glycerine). The sample pieces were mounted on the glass slides in a drop of lactic acid and were observed under low power (10x) of the light microscope. Extent of AM infection was recorded with the help of an already calibrated ocular micrometer. This was done by randomly focusing the plant material under the microscope and by measuring the hyphae. The number of vesicles and other structures were also recorded in the same way. Microphotography was done with the help of Minolta X 700 camera with the adapter tube.
Soil adhering to the roots and other portions like bulbs were utilized for screening the associated AM spores. Spore extraction was done by following wet sieving decanting method of Nicolson and Gerdemann [11,12]. Density and diversity of spores was recorded. Spores were identified using synoptic key by Morton [16] and Schenck and Perez [17]. All the data was statistically analyzed by computing Standard

Result and Discussion
AM colonization was completely absent in scales and roots of Allium cepa, and roots of Amaryllis vittata (members of Amaryllidaceae) may be attributed to existence of immunity to attack by pathogenic fungi. In bulbs of Allium cepa resistance to attack by fungus is due to the presence of catecol and protocatechuic acid in the dry, pigmented, outer scale leaves. Members of Amaryllidaceae also produce fungitoxin (Methylene-buty rolactose) in their bulbs, which also diffuses to plant roots (Figures 1-3) and (Tables 1-3).