SELECTION OF SALINITY TOLERANCT CITRUS ROOTSTOCK SPECIES

Abstract

The present investigation was carried out to study the effects of two mutagenic
agents (Sodium azid and gamma radiation) on salt tolerance of Cleopatra Mandarin
(Citrus reticulate L.) (CM), Troyer Citrange (C. sinensis (L.), C. Osbeck X C.
trifiolata (L.) (TC), Volkamer lemon (C. volkameriana) (VL) and Sour orange
(Citrus aurantium L.) (SO) grown at the Agricultural Experimental Station, Faculty
of Agriculture (El-Shatby), Alexandria University. Seedlings were treated with saline
water 6000 ppm for Sour orange, Volkamer lemon and Cleopatra mandarin and 4000
ppm for Troyer Citrange, in addition to and normal controls Alterations were
recorded for morphological characters (salt tolerance %, stem height, leaf number,
leaf area and leaf burning %), leaf chemical constituents (proline content) and leaf
element content (N, Mg, Ca, Na and Cl), the differences between each citrus
rootstock and molecular analysis RAPD were also examined to detect polymorphic
variants associated with responses under saline treatments. According to these
results, it was observed that gamma rays surpassed sodium azid in increasing leaf
number, leaf area, leaf praline content and leaf contents of Ca and Na. Meanwhile,
sodium azid caused a pronounced effect in Cl content. Moreover, no significant
differences were found in respect to tolerance to salt percentage, stem height,
burning percentage and leaf N, Mg and Cl contents due to the mutagenic materials.
Salinity had negative effects on, leaf defoliation, leaf injury, vegetative growth and
leaf and root mineral contents. Cleopatra mandarin can be considered as a salt
tolerant rootstock, meanwhile sour orange and Volkamer lemon can be considered as
moderate tolerant rootstock and Troyer Citrange was a salt sensitive rootstock.
RAPD markers can cover a high proportion of the genome because of the high
number of bands scored in each analysis, due its neutral origin, there is no guarantee
that such bands fall in coding regions of the genome involved in morphological and
agronomic traits. Morphological and RAPD analysis turned to be good tools to
identify desired plants.