Effect of Mycorrhizal Inoculation at Different Salinity Levels on Root Colonization , Growth and Chlorophyll Content of Different Grape Rootstocks ( Vitis spp )

A pot culture experiment was conducted during 2004-2006 at the College of Agriculture, University of Agricultural Sciences, Dharwad, to investigate effect of arbuscular mycorrhizal (AM) fungus ( Glomus fasciculatum ) inoculation at different salinity levels (0.52, 1.90, 4.33, 6.23 and 7.94 dSm -1 ) on root colonization, growth and chlorophyll content of four grape rootstocks (Salt Creek, Dogridge, St. George and 1613). The extent of AM response on root colonization, growth and chlorophyll content varied with rootstock species, and with the level of salinity. AM fungus inoculated plants showed significantly higher root colonization percentage, root volume, root length, number of leaves, leaf area, total dry weight, and chlorophyll content. Exposure to salinity stress resulted in decreased root colonization, chlorophyll content and growth of shoots on all rootstocks, but reduction in growth was greatest on St. George. Keywords : grape; rootstock; salinity; mycorrhiza; root colonization; chlorophyll. DOI: 10.4038/tare.v10i0.1875 Tropical Agricultural Research & Extension Vol.10 2007 79-82


INTRODUCTION
Grape (Vitis spp.) is one of the most commercially grown important fruit crops in the world.In India grapes are cultivated at an extent of 40,000 hectares across the country with an estimated production of 1.2 million tonnes (Anonymous, 2003).Maharashtra, Andhra Pradesh, Karnataka and Tamil Nadu in western and southern India, and Punjab, Haryana and Uttar Pradesh in northern India, are the major grape growing states.Over 90 per cent of the area occupied by grape cultivation is found in semi arid regions of Maharashtra, northern Karnataka and Andhra Pradesh.In the last five to six years, grape productivity in these states has been constrained by water scarcity due to regular monsoon failure and soil salinity.Saltaffected soils cover an area of nearly 13.5 M ha in India (Sharma et al., 2004) and 173 thousand ha in Karnataka (Sharma, 1998).
Salinity is an environmental stress that limits growth and development in plants.The response of plants to excess salt is complex and involves changes in their morphology, physiology and metabolism (Shannon et al., 1994).In arid and semi-arid regions of the world, limited rainfall, high evapotranspiration, high temperature and inadequate water management contribute to increase in soil salinity.In those areas, plant growth is severely affected by salinity through water deficit, salt-specific damages (Munns and Termaat, 1986) or oxidative stress (Hernandez et al., 1995).Plants" capacity to endure the effects of excessive salt in the root zone is the "salt tolerance" of plants.Plants vary in their response to soil salinity and the range of salt concentrations tolerated by crops varies greatly from species to species (Volkmar et al., 1998).

Effect of Mycorrhizal Inoculation at Different Salinity Levels on Root Colonization, Growth and Chlorophyll Content of Different Grape Rootstocks (Vitis spp)
Several greenhouse studies showed that grapevines inoculated with indigenous AM fungi had higher pruning weights and root weights (Linderman and Davis, 2001), and more compact, highly branched roots than nonmycorrhizal grapevines (Schellenbaum et al., 1991).Munns and Termaat (1986) suggested that growth inhibition in the long term exposure to increased salinity condition was related to lower photosynthetic area which will eventually become too low to support continuing growth.Munns (1993) proposed that accumulation of salt in the old leaves accelerated their death, and loss of these leaves decreased the supply of carbohydrates or growth hormones to meristematic regions, thereby inhibiting growth.Zekri (1991) concluded that salinity reduced shoot growth by suppressing leaf initiation and expansion as well as internode growth and by accelerating leaf abscission.The present study showed that salinity treatment caused significant decreases in leaf number of shoots.Decreases in the number of leaves were not only related to the growth inhibiting effects of salt, but also to the injurious effects of salt due to defoliation of the damaged leaves.Ramanujalu et al. (1993) observed gradual decrease in the contents of chlorophyll "a" and chlorophyll "b" with increase in the salt intensity in mulberry, wherein relatively higher rate of depletion was found with chlorophyll "a" than chlorophyll "b".

Table 1 . Effect of mycorrhizal inoculation and different salinity levels on root colonization, root volume and root length of grape rootstocks MATERIALS AND METHODS
Agricultural Research Station of the University of Agricultural Sciences, Dharwad (Raichur district, Northern Karnataka).To maintain level of salinity, plants were given a measured quantity of water and kept under salinity stress condition for four months.Per cent root colonization was determined following the procedure outlined byPhillips and Hayman (1970).Leaf area was determined using Portable Area Meter, Model LI-3000A, LI-COR.Chlorophyll content of the leaves was determined following dimethyl sulfoxide (DMSO) method.At the end of the experimental period, plants were carefully removed from earthen pots and shoot and root parts were separated and the roots washed in water.In order to obtain dry weight of shoot and root, fresh tissues were dried at 70 o C in an oven for 24 hours till constant weight was reached.
removed from polythene bags and imposed to different levels of salinity (0.52, 1.90, 4.33, 6.23 and 7.94 dSm -1 ), which were obtained from naturally salt affected soil in GangawatiRESULTS AND DISCUSSIONMycorrhizal inoculation and salinity stress had strong effects on growth, root colonization and leaf chlorophyll content.Growth parameters (number of leaves per vine, leaf area, root volume, root length and total dry weight) and per

Table 3 . Effect of mycorrhizal inoculation and different salinity levels on chlorophyll 'a', 'b', and total chlorophyll content of grape rootstocks cent
root colonization decreased in all the rootstocks with increase in salinity stress from 0.52 to 7.94 dSm -1 .Mycorrhiza inoculated plants recorded significantly higher root colonization percentage, root volume and root length (Table