Consuming a SOAP Webservice in c# , throwing object reference not set to an instance of an object

Question

Please check the below code which , i am trying to consume a SOAP webservice which requires an object of the type ZPLM_BOM_EXPL_MAT to be passed. I have created the object "test" and when I am assigning a value some value at the index [0] , the error "object reference " is thrown. Please help

static void Main(string[] args) {

        GetBom.ZPLM_BOM_EXPL_MAT_WEBSERVICEClient client1 = new 
        GetBom.ZPLM_BOM_EXPL_MAT_WEBSERVICEClient();
        client1.ClientCredentials.UserName.UserName = "****";
        client1.ClientCredentials.UserName.Password = "****";

        GetBom.ZPLM_BOM_EXPL_MAT test = new GetBom.ZPLM_BOM_EXPL_MAT();
        GetBom.ZPLM_BOM_EXPL_MATRequest ttt = new GetBom.ZPLM_BOM_EXPL_MATRequest();            
        test.T_PO_ITEM[0].EBELN = "4506474386";
        test.T_PO_ITEM[0].MATNR = "6644856";`
        GetBom.ZPLM_BOM_EXPL_MATResponse resp = new GetBom.ZPLM_BOM_EXPL_MATResponse();
        resp = client1.ZPLM_BOM_EXPL_MAT(test);

}