فهرست مطالب a. moieni

Fusarium wilt disease is one of the most important diseases of melon, which causes damage between 20 and 80% in melon fields. In favorable conditions, the spread of the disease can reach 100%. In the improvement programs, achieving resistant cultivars is considered one of the most important methods of controlling this disease.

In this research, 46 melon landraces were collected from different parts of Razavi, Northern and Southern Khorasan provinces, along with two separate lines, Isabel and Charente T respectively as resistant and sensitive control cultivars to identify new sources of wilt disease resistance to Fusarium oxysporum f. sp. melonis. The experiments were carried out in a randomized complete block design with three replications in the greenhouse of the agricultural campus of Tarbiat Modares University. The seeds were grown in trays containing cocopeat and perlite in a ratio of 2:1; fourteen days after cultivation, the roots of the young seedlings were removed from the culture tray and inoculated for two minutes with the isolate Mt13-3a of F. oxysporum f. sp. melonis race 1.2 spore suspension solution, with a concentration of 106 conidium per milliliter. The symptom was evaluated nine days after inoculation. The spread of symptoms on the plants was recorded every day for 30 days until the complete death of the plant. Evaluation of resistance was calculated using the indices of the area under the disease progress curve (AUDPC), latent period (LP), disease severity index (DSI), and standardized area under the disease progress curve (SAUDPC) in landraces. Investigating the variation of the resistance of the studied landraces based on the mentioned indices was done using analysis of variance and cluster analysis.

The results of the analysis of variance of the data indicated the existence of a significant difference of 1% between the landraces for all four studied indices. Based on the heat map results, there is resistance to race 1.2 of F. oxysporum f. sp. melonis in the genotype Isabel and Tude Qaenat. Also, the cluster analysis of landraces based on Ward's method led to identifying six resistance groups from the 46 landraces studied, along with two differential control lines.

The results of the present research showed that for all four indices of LP, AUDPC, DSI and SAUDPC, there is resistance to race 1.2 of F. oxysporum f. sp. melonis in Isabel genotype as a resistant control and the landraces of Qaenat, Till Magasi, Till Zard, Till Torgh, Laki 1 and Till Keshideh compared to the sensitive control (Charente T).

Androgenesis has great potential in plant breeding due to its high efficiency and applicability in many plant species. Anther culture is one of the most common technique to induce haploids in plant breeding programs. In this study, to optimize anther culture of bell pepper, the effects of four darkness periods and five concentration levels of silver nitrate were studied in four commercial hybrids; Kamelot, Inspiration, Plato and Californium. The results showed that increasing dark treatment from six to ten days, increased the percentage of embryogenic anthers and the percentage of regenerated plantlets. The highest percentages of embryogenic anthers and regenerated plantlets were obtained using 10 mg l-1 of silver nitrate and incubating anthers cultured in CP medium for 10 days in darkness. The results also showed that the highest percentage of embryogenic anthers (16.66%) was observed in the interaction effect between 10 mg l-1 of silver nitrate and cv. Plato. Also, among the studied concentrations of silver nitrates, the highest percentage of regenerated plantlets (11.71%) was obtained using 10 mg l-1 of silver nitrate.

The availability of nutrients such as phosphorus in plant, in addition to plant yield increment, could increase growth rate and thus reduce plant growth period. Therefore, identification and overexpression of genes involved in nutrient uptake are the important steps to increase of yield and tolerance to environmental stresses particularly the end seasons stresses. Purple acid phosphatases, one of the most important phosphatase family, play a key role in increasing phosphorus availability in plants. In this study, the effect of knock-out and overexpression of AtPAP17 and AtPAP26 genes (two important members of Arabidopsis thaliana purple acid phosphatase family) on some physiological and phonological traits of Arabidopsis thaliana was investigated under Pi-sufficient (1.25 mM KH2PO4) and Pi-deficient (0 mM KH2PO4) conditions. For this purpose, single and double mutant plants of AtPAP17 and AtPAP26 genes were studied in this research. To confirm the function of mentioned genes in mutant plants, transformed Arabidopsis plants containing the CaMV-35S:AtPAP17 and CaMV-35S:AtPAP26 constructs were studied as overexpressed plants of AtPAP17 and AtPAP26 genes, respectively. The result showed that biomass and phosphorus content of plants increased in single mutant plants as compared to double mutant plants under Pi-sufficient condition. Superiority of single mutant plants as compared to double mutant plants indicated a remarkable contribution of AtPAP17 and AtPAP26 genes in phosphatase compensation network. Our results showed at least one of these genes (AtPAP17 and AtPAP26) activity is essential for increasing phosphorus availability and fast growth in Arabidopsis thaliana. Also, overexpressed plants displayed a significant increase in phosphorus content, flowering percentage, and biomass as compared to WT plants (Col-0). The results of this study showed that AtPAP17 and AtPAP26 genes could be important candidates for developing the plants with high ability of nutrient uptake, especially phosphorus, thereby reducing plant growth period.

In this paper, we introduce the novel parameters indicating Normalized Tenacity ($T_N$) and Normalized Toughness ($t_N$) by a modification on existing Tenacity and Toughness parameters.  Using these new parameters enables the graphs with different orders be comparable with each other regarding their vulnerabilities. These parameters are reviewed and discussed for some special graphs as well.

In Order to evaluated resistance to yellow rust in some doubled haploid lines and their parents in the spring hexaploid wheat, fourty doubled haploid lines together with their parents (Ghods, 9106 and 6605), and two cultivars Bolani (Susceptible check) and Triticum spelta var. album (Resistant check) in a randomized block design with three replications were tested in the greenhouse conditions in seedling stage to four races 134E134A+ , 38E2A- , 7E18A- and 230E62A+ of yellow rust. Resistance components measured were latent period (L. P.) and infection type (I. T.). The results showed that, some doubled haploid lines were resistant to the races of yellow rust, e.g. line (GH 91) DH3 was resistant (I. T. = 2) to race 134E134A+ , in spite of the susceptibility of both parents.