3.0拓扑图，如果去除红色圆圈？echarts tree配置项内容和展示

如题，想自定义样式。怎么也去不掉红色圆圈，求助！！

      var testData = {
    name: "test",
    children: [{
        name: "test1",
        children: [{
            name: "test1_1",
            value: 100
        }, {
            name: "test1_2",
            value: 100
        }]
    }, {
        name: "test2",
        children: [{
            name: "test2_1",
            value: 120
        }, {
            name: "test2_2",
            value: 120
        }]
    }]
};
option = {
    tooltip: {
        trigger: 'item',
        triggerOn: 'mousemove'
    },
    series: [{
        type: 'tree',
        data: [testData],
        top: 45,
        left: 15,
        right: 5,
        bottom: 15,
        symbol: 'emptyCircle',//如何去除红色圈圈？
        //symbol: 'none',//整个图形不见
        //自定义图片，有红色边界。怎么去除？或者样式可以自定义吗？
        //symbol:'http://tb.himg.baidu.com/sys/portrait/item/96f2613235323333323234306b0c',
        symbolSize:20,
        //symbolSize:0,//设置为0，文本标签页不见了
        orient: 'vertical',
        expandAndCollapse: true,
        label: {
            normal: {
                position: 'top',
                rotate: -90,
                verticalAlign: 'middle',
                align: 'right',
                fontSize: 19
            }
        },
        itemStyle:{
            borderWidth:0
        },
        leaves: {
            label: {
                normal: {
                    position: 'bottom',
                    rotate: -90,
                    verticalAlign: 'middle',
                    align: 'left'
                }
            }
        },
        animationDurationUpdate: 750
    }]
};