| Tomato(Solanum lycopersicum L.) as one of the important economic crops is widely cultivated all over the world, which plays an important role in people’s daily diet and nutrition intake. Several problems are exsited in the current process of tomato breeding and seed production. For example, the genetic basis of tomato varieties are narrow because only a small number of key breeding parents used in breeding, and the level of hybrid seed purity testing and the seed vigor of varieties is low. Therefore, the SSR technology was used to analysis the genetic diversity in inbred lines of different tomato types in this study, the SSR technology was used to build a rapid tomato seed purity testing system, and the seed priming technology was used to improve the seed vigor. The main results obtained are as follows:1. Seed vigor of105core collection was identified under normal, salt and drought stress conditions in tomato. The results showed that the amplitude of germination potential (GP) and germination rate (GR) were0to98%and0to98%under normal conditions; the amplitude of GP and GR were0to98%and0to98%under10%PEG drought stress conditions; the amplitude of GP and GR were0to52%and0to66%under100mM NaC1stress conditions. There were significant differences in GP and GR between varieties. The GP of most varieties were80to100%,80to100%and0%, respectively, the percentages were42.86%,47.6%and69.5%of total germplasm under normal, drought and salt stress conditions. However, the GR of most varieties were80to100%,80to100%and<10%, respectively, the percentages were55.23%,60.95%and63.80%of total germplasm under normal, drought and salt stress conditions. The varieties with high seed vigor were also screened in this study. For example,20varieties with high vigor seeds (GR, GP>90%) were screened and the percentage was19%of total germplasm under normal conditions;22varieties with high vigor seeds (GR, GP>90%) were screened and the percentage was20.9%of total germplasm under10%PEG drought stress conditions;4varieties with high vigor seeds (GR, GP>50%) were screened and the percentage was3.8%of total germplasm under100mM NaC1stress conditions. These tomato germplasm will benefit to the cultivation of tomato varieties with high seed vigor and to gene mapping and cloning in future study.2. A study was conducted to determine the genetic diversity of39determinate and indeterminate tomato inbred lines collected from China, Japan, S. Korea, and USA. Using35SSR polymorphic markers, a total of150alleles were found with moderate levels of diversity, and a high number of unique alleles existing in these tomato lines. The mean number of alleles per locus was4.3and the average polymorphism information content (PIC) was0.31. Unweighted Pair Group Method with Arithmetic Mean (UPGMA) clustering at genetic similarity value of0.85grouped the inbred lines into four groups, where one USA cultivar formed a separate and more distant cluster. The most similar inbred lines are from USA, both with determinate type, whereas the most different lines are from USA (Us-16) and Japan (Ja-2) with determinate and indeterminate growth habit, respectively. Clustering was consistent with the known information regarding geographical location and growth habit. The genetic distance information reported in this study might be used by breeders when planning future crosses among these inbred lines.3.35SSR markers were used to screen the polymorphic and co-dominant markers among tomato hybrids and their parents. The results indicated that16SSR markers showed polymorphic in the parents in which7SSR markers were co-dominant performance. The co-dominant SSR markers (AI778183、SSR136、LEat014) that could amplify clear and stable bands were selected to identify the accuracy of SSR testing in different artificial configuration purity of tomato samples, and the testing of field also was conducted. The similar results were found between the SSR and field testing with error about1%. The SSR testing system of seed purity will be broadly applied in future with the advantages of rapid and accurate identification in tomato.4. Priming is a pre-sowing treatment that improves seed vigor under stress conditions. This study investigates the effect of osmopriming on seed vigor under aging and salinity stress of a tomato hybrid. Tomato seeds of the ZZ1hybrid variety, stored for four years under natural (aged) or-20℃(unaged) conditions, were primed in10%(w/v) polyethylene glycol (PEG) solution for2d at20±1℃in the dark. The vigor of primed, aged seeds under normal condition (water) at25±1℃for7d was evaluated. The results showed that the germination potential (GP), germination rate (GR) and germination index (GI) of primed, aged seeds were significantly enhanced, with a substantial increase in the radicle length (RL), shoot length (SL) and total fresh weight (FW) and a reduction of the mean germination time (MGT) compared with unprimed, aged seeds. The vigor of aged seeds was comparable to that of unaged seeds due to the priming treatment. Furthermore, the vigor of primed, unaged seeds was evaluated under the100mM NaCl condition at25±1℃for7d. Similarly, the GP, GI and FW significantly increased in primed seeds compared with unprimed seeds under salinity stress. In contrast, MGT significantly decreased, while GR, RL and SL did not show significant differences. Under the field condition, the priming of tomato seeds significantly improved the stand seedling establishment and the seedlings from primed seeds had greater RL, SL, FW than the un-primed seeds. Among priming treatments, further results showed that osmopriming could reduce seed lipid peroxidation. A decline in the relative electrolyte leakage (REL) and in malondialdehyde (MDA) was detected in primed seeds during the imbibition stage compared with unprimed seeds under aging and salinity stress. Similarly, there were negative correlations between seed vigor and REL and MDA, which suggests that seed priming improves seed vigor under stress conditions associated with a decrease in lipid peroxidation. |
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