Physiological Tests on Soybean Mutant Lines against Stem Rot Disease Athelia Rolfsii Curzi Paisal Mizra Mulyadi 1 , Diana Sofia Hanafiah 2 , Revandy Iskandar Muda Damanik 3 , Irda Safni 4 , Luthfi Azis Mahmud Siregar 5 {pmanday.pm@gmail.com 1* , dedek.hanafiah@yahoo.co.id 2 , damanik_revandy@hotmail.com 3 } 1,2,3 Agroecotechnology Departmen, Faculty of Agriculture, Universitas Sumatera Utara, Indonesia *pmanday.pm@gmail.com Abstract. Soybean plants are often attacked by soil fungi that cause the plants to become wilted and generally caused by Athelia rolfsii Curzi. The research aims to test the physiology of soybean mutant lines against the stem rot disease of Athelia rolfsii Curzi. The results of data analysis showed that the inoculation of fungi to soybean mutant lines increases the content of the enzyme SOD and POD’s in each soybean genotypes. There are lines selected with the character resistant to stem rot A. rolfsii Curzi namely M100 A17 (18/5), M100 A25 (3/7), M200 A17 (18/5) and M200 A12 (6/5). Keywords: soybean, mutant lines, Athelia rolfsii Curzi, SOD, POD 1 Introduction The efforts that can be done in increasing genetic diversity and the improvement of varieties to obtain superior varieties can be made through the induction of genetic mutations. One way that can be done with physical mutagen. The physical mutagen is as ionizing radiation, one of them is gamma ray [1]. One of the technological innovations that can improve soybean productivity is the use of superior varieties. In the period from 1918 to 2015 there are 83 varieties of soybeans that have been removed and sought to be distributed to farmers. These superior varieties have a variety of potential character outcomes, harvest age, seed size, seed skin color, resistance to biotic/abiotic stress, and adaptation areas [2]. One of the common fungi is A.rolfsii Curzi often attack soy, green beans, and peanuts in the gardens scope of the crops research of legumes and tuber-Umbian (Iletri). The results of identification of diseases of the plants that are attacked wilt generally show the disease caused by A.rolfsii Curzi. A.rolfsii Curzi fungus survives in the soil or remnants of plants in the form of Hyfa or Sclerotia as microorganisms that are of facultative parasites. A.rolfsii Curzi is the cause of the stem rot at the soybean crop. The fungus will live as saprophytes when the host plant is not found. In humid conditions, this fungus is also infected with soybean branches and leaves that are near the ground. Such microorganisms have the ability of low saprophyte competition activity [3]. The damage can caused by A.rolfsii Curzi can trigger changes to physiological, such as membrane disorders, nutrient imbalance, impairs the ability to detoxify reactive oxygen species (ROS). The concentration of ROS formed for the value of the highest SOD activity shows the plant to recovery itself to overcome the hick against the stem rot disease. The high IC2RSE 2019, December 04, Medan, Indonesia Copyright © 2020 EAI DOI 10.4108/eai.4-12-2019.2293809