MARKERS ASSISTED SELECTION FOR SALT TOLERANCE AMONG SOME COTTON (Gossypium barbadense L.) GENOTYPES.

Abstract

Ten Egyptian cotton genotypes were evaluated at normal and saline soil conditions for yield and fiber properties through two years. The data revealed that increasing salt concentration in soil solution leads to significantly decreasing in seed cotton yield and other yield related characters except for lint percentage which showed increasing values under saline condition. Under saline condition, plant height was greatly reduced in high for about 37-52%, followed by reduction in number of fruiting sympodia of about 49-72% as compared with normal condition. Therefore, the reductions in cotton yield under stress condition, in generally, due to reduction in boll production primarily because of fewer flowers and less boll number due to increased boll abortions. Among the cotton genotypes, Giza 86 followed by Giza 94 recorded high seed cotton yield under both conditions and these genotypes recorded the minimum reduction in seed cotton yield under saline condition. The first three principal components PC were significant (p> 0.01) and accounted for 84.62 among genotypes variance with Eigen values more than unity. The first principal components accounted for maximum variability in the data with respect to succeeding components. PC1 explained for about 41.502% of the total variability amongst genotypes with the largest Eigen values 5.395 and dominated by a large loading for most yield and fiber characters i.e., seed cotton yield, lint yield, boll weight, seed index, lint index, micronaire reading and susceptibility index. In the second PC axis, plants with high fiber length and length uniformity with decreased in first node influenced by a reduced in lint percentage and other yield potential with decreased fiber fineness. The rest axis accounted about 10.91% of the total variability and domintialy affected by sympodial branches. Under saline condition the ten cotton genotypes were grouped into six major clusters on the basis of dissimilarity among genotypes and relative contribution of evaluated characters. The data revealed that cluster 3 showed the highest seed cotton yield (K/Fed) and either yield attributed characters with acceptable fiber properties. This cluster contained one genotype, Giza 86, and characterized by high susceptibility index for saline condition. Seventy five out of 109 bands were polymorphic and representing 80% of the total generated bands with an average of 6.25polymorphic bands per primer, showing considerable genetic variation among the ten cotton genotypes. Based on RAPD data analysis, the similarity matrix among the 10 varieties ranged from 0.738 to 0.94. The highest similarity value revealed was between Giza-92 and Giza-70 (0.94), while the lowest similarity value was shown between Giza-94 and Giza-93. The dendrogram separated all genotypes into two main groups where Giza-86 was placed in one group and all other genotypes were placed in the second one. This distribution clearly agreed with the performance of Giza 86 as the best genotype comparing with others according to vegetative traits studied and yield and its attributes. Results from morphological measurements and RAPD markers are complementary for each other in studying and understanding the genetic control of saline tolerance in plant population, and both gave essential information for understanding genetic divergence of Egyptian cotton germplasm.