Phenotypic characterization and molecular evaluation were compared in their differentiating influence and quantity of information to assess the genetic diversity in guava. Forty nine genotypes were analyzed phenotypicaly using eleven quantitative traits; out of them ten were selected for the comparison. Analysis of variance showed highly significant differences amongst guava genotypes in all traits except total sugar content. On the other hand, the sequence related amplified polymorphism (SRAP) was used for the molecular analysis. A total of 88 SRAP amplicons were generated by five primer combinations, of which 58 bands (65.9%) were polymorphic. Both cluster analysis of unweighted pair-grouping method with arithmetic averages (UPGMA) and principal coordinate (PCO) analysis based on phenotypic data and SRAP clearly separated the genotypes according to their relationships. However, the clustering arrangement was different depending on the data used for the analysis. In addition, the percentage of polymorphism amongst the tested genotypes varied between the two marker systems. SRAP marker was able to generate some unique specific bands for certain genotypes which could be helpful for further use in guava genetic enhancement.

Phenotypic characterization and molecular evaluation were compared in their differentiating influence and quantity of information to assess the genetic diversity in guava. Forty nine genotypes were analyzed phenotypicaly using eleven quantitative traits; out of them ten were selected for the comparison. Analysis of variance showed highly significant differences amongst guava genotypes in all traits except total sugar content. On the other hand, the sequence related amplified polymorphism (SRAP) was used for the molecular analysis. A total of 88 SRAP amplicons were generated by five primer combinations, of which 58 bands (65.9%) were polymorphic. Both cluster analysis of unweighted pair-grouping method with arithmetic averages (UPGMA) and principal coordinate (PCO) analysis based on phenotypic data and SRAP clearly separated the genotypes according to their relationships. However, the clustering arrangement was different depending on the data used for the analysis. In addition, the percentage of polymorphism amongst the tested genotypes varied between the two marker systems. SRAP marker was able to generate some unique specific bands for certain genotypes which could be helpful for further use in guava genetic enhancement.

Phenotypic characterization and molecular evaluation were compared in their differentiating influence and quantity of information to assess the genetic diversity in guava. Forty nine genotypes were analyzed phenotypicaly using eleven quantitative traits; out of them ten were selected for the comparison. Analysis of variance showed highly significant differences amongst guava genotypes in all traits except total sugar content. On the other hand, the sequence related amplified polymorphism (SRAP) was used for the molecular analysis. A total of 88 SRAP amplicons were generated by five primer combinations, of which 58 bands (65.9%) were polymorphic. Both cluster analysis of unweighted pair-grouping method with arithmetic averages (UPGMA) and principal coordinate (PCO) analysis based on phenotypic data and SRAP clearly separated the genotypes according to their relationships. However, the clustering arrangement was different depending on the data used for the analysis. In addition, the percentage of polymorphism amongst the tested genotypes varied between the two marker systems. SRAP marker was able to generate some unique specific bands for certain genotypes which could be helpful for further use in guava genetic enhancement.

Ziziphus spinia-christi and Z. mauritiana are known as "Balady" and "Hendi" cultivars, respectively in Egypt. They were used in this study to analyze the genetic diversity of Egyptian Ziziphus and to authenticate a new superior cultivar namely "Hozaien". This cultivar arose more than fifty years ago and has been reported as a bud sport mutation of "Balady" cultivar despite its extremely morphological and biochemical variations. The sequence related amplified polymorphism (SRAP) and the randomly amplified polymorphic DNA (RAPD) molecular markers were utilized to analyze the genetic relationships amongst the three cultivars. A total of 141 SRAP and 75 RAPD amplicons were generated by 10 SRAP and 6 RAPD primer combinations; of which 87 (61.70%) and 32 (42.67%) bands were polymorphic, respectively. SRAP was more informative and showed more shared and specific unique bands than RAPD. Both cluster analysis and principal coordinate analysis based on SRAP and RAPD data clearly showed that "Hozaien" cultivar has low genetic relationship with Z. spina-christi and should not be classified as a mutant of it. This result encourage us to detach this cultivar from which and subject it for more study, using more species from neighbor countries, to voucher its identity either a cultivar of another species or a new species.

Ziziphus spinia-christi and Z. mauritiana are known as "Balady" and "Hendi" cultivars, respectively in Egypt. They were used in this study to analyze the genetic diversity of Egyptian Ziziphus and to authenticate a new superior cultivar namely "Hozaien". This cultivar arose more than fifty years ago and has been reported as a bud sport mutation of "Balady" cultivar despite its extremely morphological and biochemical variations. The sequence related amplified polymorphism (SRAP) and the randomly amplified polymorphic DNA (RAPD) molecular markers were utilized to analyze the genetic relationships amongst the three cultivars. A total of 141 SRAP and 75 RAPD amplicons were generated by 10 SRAP and 6 RAPD primer combinations; of which 87 (61.70%) and 32 (42.67%) bands were polymorphic, respectively. SRAP was more informative and showed more shared and specific unique bands than RAPD. Both cluster analysis and principal coordinate analysis based on SRAP and RAPD data clearly showed that "Hozaien" cultivar has low genetic relationship with Z. spina-christi and should not be classified as a mutant of it. This result encourage us to detach this cultivar from which and subject it for more study, using more species from neighbor countries, to voucher its identity either a cultivar of another species or a new species.

Vitamin-C content (VCC) was evaluated in 74 guava landraces using direct titration method with iodine during two seasons. Results showed that the highest value of VCC was 284.0±1.33, while the lowest VCC was 152.83±1.83 with an average of 221.26±3.17 mg/100g fresh weight. Analysis of variance showed the presence of highly significant differences among the tested landraces, as well as the interaction between landraces and seasons. Data of VCC showed normal distribution with high values of both broad sense heritability (0.97) and genetic advance (78.49) indicating high ability for selection. On the other hand, molecular analysis was performed using two molecular markers, i.e. sequence related amplified polymorphism (SRAP) and inter sequence simple repeats (ISSR) to determine unique and specific bands for high or low VCC. SRAP was more informative than ISSR and was able to generate 12 specific bands. Among these bands, 10 bands were specific for bulked DNA of landraces with high VCC, while the other two bands were specific for low VCC. However, ISSR only showed four bands where all of them were specific for low VCC. Results of this study gave good information for genotype selection for high VCC which could be used in guava breeding programs and/or biotechnological approaches. In addition, the specific bands generated by SRAP might assist in rapid screening for genotypes with high VCC, which could be identified in seedling or graft stage, therefore this would save time in a plant with long juvenile period like guava. Furthermore, these bands would be analyzed by sequencing in subsequent studies to locate related genome regions.

Vitamin-C content (VCC) was evaluated in 74 guava landraces using direct titration method with iodine during two seasons. Results showed that the highest value of VCC was 284.0±1.33, while the lowest VCC was 152.83±1.83 with an average of 221.26±3.17 mg/100g fresh weight. Analysis of variance showed the presence of highly significant differences among the tested landraces, as well as the interaction between landraces and seasons. Data of VCC showed normal distribution with high values of both broad sense heritability (0.97) and genetic advance (78.49) indicating high ability for selection. On the other hand, molecular analysis was performed using two molecular markers, i.e. sequence related amplified polymorphism (SRAP) and inter sequence simple repeats (ISSR) to determine unique and specific bands for high or low VCC. SRAP was more informative than ISSR and was able to generate 12 specific bands. Among these bands, 10 bands were specific for bulked DNA of landraces with high VCC, while the other two bands were specific for low VCC. However, ISSR only showed four bands where all of them were specific for low VCC. Results of this study gave good information for genotype selection for high VCC which could be used in guava breeding programs and/or biotechnological approaches. In addition, the specific bands generated by SRAP might assist in rapid screening for genotypes with high VCC, which could be identified in seedling or graft stage, therefore this would save time in a plant with long juvenile period like guava. Furthermore, these bands would be analyzed by sequencing in subsequent studies to locate related genome regions.

Forty landraces of guava were subjected to drought tolerance evaluation based on in vitro polyethylene glycol (PEG) treatment. Nodal stem segments with lateral buds were used as explant. Five concentrations (i.e. 0, 4, 6, 8 and 10%) of PEG were tested, among which the optimum concentration for screening was determined as 8%. Analysis of variance showed highly significant variation among the tested landraces, concentrations of PEG and the interaction between them in the percentage of response (%R), number of shoot per explant (NSE) and drought susceptibility index. The average percentage of reduction due to PEG treatment was 48.30 and 52.57% for the %R and NSE, respectively. Heritability and genetic advance were increased due to drought stress for %R, while they were decreased for NSE, indicating that %R was more related to drought stress than NSE. The molecular analysis of the highest and lowest responsive landraces was performed using sequence related amplified polymorphism (SRAP) and inter-simple sequence repeats (ISSR). Both markers were effective in discriminating the tested landraces and completely separated them into two clusters related to %R under PEG. ISSR showed a higher percentage of polymorphism, polymorphic information content and diversity index compared with SRAP. However, SRAP was more effective than ISSR in showing a higher primer resolving power and a number of unique specific bands for drought tolerance and susceptibility. Drought in vitro evaluation method established here is effective, inexpensive and manageable in genotype screening for drought tolerance in guava and could be used in other woody plant species.

Forty landraces of guava were subjected to drought tolerance evaluation based on in vitro polyethylene glycol (PEG) treatment. Nodal stem segments with lateral buds were used as explant. Five concentrations (i.e. 0, 4, 6, 8 and 10%) of PEG were tested, among which the optimum concentration for screening was determined as 8%. Analysis of variance showed highly significant variation among the tested landraces, concentrations of PEG and the interaction between them in the percentage of response (%R), number of shoot per explant (NSE) and drought susceptibility index. The average percentage of reduction due to PEG treatment was 48.30 and 52.57% for the %R and NSE, respectively. Heritability and genetic advance were increased due to drought stress for %R, while they were decreased for NSE, indicating that %R was more related to drought stress than NSE. The molecular analysis of the highest and lowest responsive landraces was performed using sequence related amplified polymorphism (SRAP) and inter-simple sequence repeats (ISSR). Both markers were effective in discriminating the tested landraces and completely separated them into two clusters related to %R under PEG. ISSR showed a higher percentage of polymorphism, polymorphic information content and diversity index compared with SRAP. However, SRAP was more effective than ISSR in showing a higher primer resolving power and a number of unique specific bands for drought tolerance and susceptibility. Drought in vitro evaluation method established here is effective, inexpensive and manageable in genotype screening for drought tolerance in guava and could be used in other woody plant species.

Forty landraces of guava were subjected to drought tolerance evaluation based on in vitro polyethylene glycol (PEG) treatment. Nodal stem segments with lateral buds were used as explant. Five concentrations (i.e. 0, 4, 6, 8 and 10%) of PEG were tested, among which the optimum concentration for screening was determined as 8%. Analysis of variance showed highly significant variation among the tested landraces, concentrations of PEG and the interaction between them in the percentage of response (%R), number of shoot per explant (NSE) and drought susceptibility index. The average percentage of reduction due to PEG treatment was 48.30 and 52.57% for the %R and NSE, respectively. Heritability and genetic advance were increased due to drought stress for %R, while they were decreased for NSE, indicating that %R was more related to drought stress than NSE. The molecular analysis of the highest and lowest responsive landraces was performed using sequence related amplified polymorphism (SRAP) and inter-simple sequence repeats (ISSR). Both markers were effective in discriminating the tested landraces and completely separated them into two clusters related to %R under PEG. ISSR showed a higher percentage of polymorphism, polymorphic information content and diversity index compared with SRAP. However, SRAP was more effective than ISSR in showing a higher primer resolving power and a number of unique specific bands for drought tolerance and susceptibility. Drought in vitro evaluation method established here is effective, inexpensive and manageable in genotype screening for drought tolerance in guava and could be used in other woody plant species.