Hesham Fouzat Alatwani
Sweida Research Center-
General Commission for Scientific Agricultural Research
Faculty of Agriculture, Cairo University, Egypt
Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Agricultural Sciences (Genetics)
Abstract
This study included two main parts. The first part, genetic variability and relationships among seven cotton genotypes, including 3 Egyptian cotton varieties (Giza 80, 86 and 90) , 3 Syrian upland cotton varieties (Deir Ezzor22, Rakka 5 and Aleppo40) and the USA Delta pine cotton variety were investigated using 14 RAPD, 12 ISSR and 5 AFLP primers or primer combinations. The number of polymorphic amplicons was 79, 62 and 291, respectively. The levels of polymorphism as detected by RAPD, ISSR, and AFLP were 71.81, 88.57 and 50.52%, respectively. Based on the RAPD, ISSR, AFLP and combined data , the genetic similarities according to Dice ranged from 64.8 to 93.2% , 29.4 to 87%, 79.4 to 87.9% and 76 to 86%, respectively. All dendrograms clustered the 7 cotton genotypes into two main clusters, one containing the 4 cotton genotypes belonging to hirsutum and the other one containing the 3 genotypes belonging to barbadense. The seven cotton genotypes were characterized by 34 RAPD markers, 13 ISSR markers and 87 AFLP markers. To evaluate the efficiency of the different marker systems, the sum of effective number of alleles (SENA), the average expected heterozygosity for polymorphic markers (Hav(p)), the effective multiplex ratio (E) and marker index (MI) were calculated. The AFLP exhibited considerably high SENA (274.95) compared to RAPD and ISSR (36.19 and 32.14, respectively). The average heterozygosity values were comparable for the different marker systems (0.228, 0.284 and 0.272 in RAPD, ISSR and AFLP, respectively). The MI was 79.52 in AFLP™s, while it was 18.12 and 18.17 in RAPD and ISSR, respectively. Thus, the results indicated that AFLP was the most efficient in detecting polymorphism. In the second part of this study, the yield components and fiber quality traits of 20 F4™s and 20 F5™s produced from a diallel mating design of five Egyptian cotton varieties were evaluated in two experiments. The cross Giza 89 X Giza 70 showed good performance for most of studied traits as bulked seed or single plant progenies. Highly significant correlation was detected between seed cotton yield per plant and plant height, number of fruiting branches, lint cotton yield per plant and lint percentage. Path coefficient analysis showed that lint cotton yield/plant (LCY/P) had a maximum positive direct effect on seed cotton yield/plant (SCY/P)(0.579) followed by plant height (0.385) and number of fruiting branches (NFB/P) (0.373). The broad sense heritability showed highest values in single plant progenies than in bulked populations. Giza89 X Giza70 showed the highest and significant superiority for NFB/P, SCY/P and LCY/P in bulk populations and single plant progenies.
Key words:Cotton, polymorphism, RAPD, ISSR, AFLP, genetic relationships, SENA,heterozygosity, multiplex ratio, bulk populations, single-plant progenies, path coefficient, heritability