| Garlic (Allium sativum) is one of the most important plants used as vegetable, spice and flavoring agent for foods and medicine. China is the main producer of garlic in the world, with the production accounting for77.4%of the world. Additionally, Egypt is the fourth producers with the highest average yield of25.287ton/ha recorded. However, limited natural variation can not meet the requirement for genetic improvement and little breeding work for higher yield, good quality and resistance to biotic and a biotic stress has been done so far since garlic does not reproduce sexually. In addition, it is difficult to measure the secondary metabolic components and characterize the genetic variation accurately by conventional methods. So, it was important to discover elite germplasm and create new variants. UPLC as an effective method has developed for allicin quantification. SSR markers as a co-dominant marker have many advantages in identifying genetic variation. Mutagenesis based on tissue culture techniques may offer an effective method in improving vegetative propagated plants. For these reasons, three experiments were carried out:Firstly, assessment of impact of genetic and environment factors on allicin content in garlic germplasm from Egypt and China, Secondly, estimation of genetic diversity among garlic germplasms based on morphological traits and new SSR primers, lastly, somaclonal mutagenesis technology by gamma radiation and ethyl methane sulphonate (EMS) treatment on garlic callus. The main results are summarized as follows:1. Impact of genetic and environment factors on allicin content of garlic germplasmAllicin contents were quantified among104garlic germplasms (83accessions from China and21from Egypt) by UPLC. All germplasm were clustered into four groups based on allicin content. The germplasms with the highest allicin content clustered into Group A, which comprises one germplasm from Egypt and one from China. Cluster analysis revealed a wide range of variation in allicin content among these garlic germplasms, which can be exploited by selection in garlic breeding programs to improve garlic quality. It was found that some selected clones had higher allicin content than their parents, which shows that clone selection from a natural population can be effective for genetic improvement in garlic. The effects of germplasm, geographical location, and the interaction between germplasm and geographical location on allicin content (P<0.001) of Egyptian garlic germplasm were all highly significant. Egyptian garlic germplasms grown in China had lower allicin content than that grown in Egypt. The reduction in allicin content of the same germplasm grown in these two locations ranged from16%to63.7%. This finding confirmed that the choice of garlic growing region is of critical importance for improving allicin content for the garlic industry. 2. Estimation of garlic genetic diversity based on morphological traits and new microsatellite markersGenetic diversity of Chinese (83accession) and Egyptians (21accession) garlic germplasms have been analyzed using19morphological characters and16new microsatellites (SSR) primers developed upon transcriptome sequencing. These designed16new microsatellites primers generated44alleles among all accessions and the numbers of alleles per primers pair ranged from1to4with average polymorphic alleles per locus were2.75. The allele frequency ranged from0.5048to0.9615. The gene diversity ranged from0.0740to0.5000. Moreover, the hetrozygosity ranged from0.0481to0.9904and the average of PIC was0.2225. The obtained cluster tree based on morphological characters separated the germplasms into two major groups. However, dendrogram constructed based on SSR data using16novel microsatellites, divided the104garlic germplasm into three main clusters. Furthermore, there is a notice that both of dendrograms were almost in accordance with geographical location. In addition,12primers of16novel SSR primers confirmed the genetic variation between the clonal offspring selected and its parent, which proved that clonal selection could be effective method for garlic improvement.3. Study of mutation induction technology from garlic callus by gamma raysCallus of two Chinese garlic varieties (’Yong Nian’ and ’Zhong Mou’) were exposed to1,3,5and7Gray of gamma radiation. The obtained results revealed that YN was sensitive to high dose of gamma ray, while the variety ZM was the better performing variety for all growth parameters at higher gamma ray doses. More specifically, the average number of callus producing sprouts, sprout number per callus, total number of sprouts, the number of sprouts forming plantlets and plantlet’s length (which were33.33,2.37,296.00,170.00and13.32cm, respectively) were higher when callus was treated with1Gy in variety YN compared with other dosages. Whereas, in the former phenotype,10.33,3.00,92.00,78.00and17.10cm for the same parameters, respectively were higher in variety ZM at7Gy. Furthermore, days for bud emergence in ZM were shorter (154d) at4Gy irradiation treatment. However,129.7days were needed for variety YN callus treated with1Gy. SSR analysis showed that two primers out of16novel primers detected out genetic variation among treated materials. Two mutants were obtained from ’Yong Nian’when callus were treated with5Gray while one mutant was created in ’Zhong Mou’callus treated with7Gray of gamma rays. It could be found5-7gray of gamma ray could be the effective dosage for induction of genetic variations (mutation).4. Effect of EMS treatments on performance of garlic callus, regenerated sprouts and formed plantlets.In this investigation, it was observed that different genotypes responded to EMS in different ways. Certain concentration and exposure time of EMS were effective to initiate the callus to differentiate and enhance the sprout to growth only on ZM callus. However, all treatment combinations even control failed to induce sprouts in YN callus and the treated callus turned to browning.The main results from ZM showed that the reduction in the average number of sprouts per callus, total number of sprouts, number of sprouts forming plantlets, plantlet length and root number were observed with the increase in the concentration of EMS and its exposure duration. More specifically, the maximum value for previous most parameters above were recorded when the callus was treated with lowest EMS concentration (0.2%) for short duration (1h). However, the maximum root length was observed in the plantlet formed from callus subjected to0.2%of EMS for2h. Moreover, the most leave number was obtained from0.4%of EMS for2hour. Additionally, the treated callus with0.5%for3h gave the biggest bulblet diameter. From phenotypes, there are potential genetic variations. |
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