Interactions with mycoriza and Phytophthora citrophthora in some citrus rootstocks

With the global climate change, the rapid increase in the world population inversely proportional to the decrease in productive agricultural production areas has brought along reliable food. Agricultural production must be increased in a sustainable way in order to reliably meet the food needs of future generations. Thus, it will be possible to contribute to the sustainability of agricultural supply. In this context, one of the most effective methods that can be used in sustainable agricultural production is the use of microorganisms that are beneficial to the environment and human health. At the beginning of these organisms, Bacillus spp. "Root Bacteria Stimulating Plant Growth", which also includes the species. Bacillus spp. species have a supportive effect on plant growth and development in terms of their positive properties such as facilitating the intake of plant nutrients and promoting the secretion of phytohormones. In addition, beneficial fungi, which are in close relationship with plant roots in the rhizosphere, are one of the most researched areas in agricultural production. Trichoderma fungi and mycorrhizal fungi are among the most frequently studied microorganisms among beneficial fungi. In particular, mycorrhizal fungi are in a symbiotic relationship with plant roots based on mutual water-nutrient exchange. These fungi ensure the integrity of the soil, facilitating the uptake of nutrients needed by the plant from the soil. Bacillus spp., Trichoderma spp. Due to the many advantages they provide to plants, mycorrhizal fungi contribute to the growth of plants in a healthier way by promoting plant growth and development. The use of such beneficial plant production will contribute to the sustainability of food supply security in the coming years. Citrus is one of the most cultivated fruit groups both in our country and in the world, with a high commercial value and an important source of income in terms of agriculture. However, citrus cultivation in the world and in our country is adversely affected by many biotic and abiotic factors. At the beginning of these negative factors are the problems related to biotic stress. One of the most important biotic stress factors in citrus fruits is Phytophthora citrophthora, which causes brown rot and stem mucilage in fruits. This disease factor causes high losses in both yield and quality in citrus orchards. Based on these problems, this study was planned to evaluate the pathogenicity of P. citrophthora isolate against Citrus and Carrizo citrange rootstocks and their relationship with other applications, and also to evaluate the use of microbial fertilizers (Trichoderma spp. It is aimed to determine the possibilities of using it in control. This research was carried out in the greenhouses of Akdeniz University, Faculty of Agriculture, Department of Horticulture in 2022-2023. As a plant production material, a 1.5 L pot type was used together with the Citrus rootstocks and Carrizo citrange rootstocks. As a microbial fertilizer, Trichoderma spp. and Bacillus spp. species, in cocktail form as mycorrhiza Glomus spp. IBA was also tested as an auxin, along with some species. The P. citrophthora isolate obtained from the Western Mediterranean Agricultural Research Institute (BATEM) was used as the disease agent. Microbial fertilizer, mycorrhiza and auxin applications were applied by dipping the bare plant roots into the prepared mixtures during the transplanting of the seedlings into the pots, and the mixtures were prepared again at the same rate in the following periods and applied 4 times in total, at 7-day intervals, to the root zone of each seedling as 50 ml. A mixture of peat, perlite, cockpit and sand at a ratio of 2:2:1:1 was used as the medium. In the study, besides the climatic data, the tolerance of rootstocks to P. citrophthora, the antagonistic effects of microbial fertilizer, mycorrhiza and auxin applications against the development of the disease and the prevention of disease formation in rootstocks were investigated. As a result of the research, Trichoderma spp. and Bacillus spp. the effect of the use of seedlings on seedling growth and development significantly contributed to the control group. In addition, applications using mycorrhizal fungi in increasing the fresh and dry weights of underground organs of seedlings gave the most positive results compared to other applications. It was determined that auxin applications did not provide statistically significant contributions to the development of underground and above-ground organs of seedlings.