watershed segmentation result not proper

Hello,

I applied watershed segmentation on Intensity Image, and you see the result in image-1. It's not proper to exract the leaf exactly. How can I fix this problem? How can I get target leaf (first and biggest) as largest region? Please see also below image-2 (marker image), image-3 (orginal image) and my code.

Thanks in advance.

image-1:

image-2:

image-3:

my code:

% I--> intensity image
% Gmag--> gradient mag.

se = strel('disk', 30);

Ie = imerode(I, se);
Iobr = imreconstruct(Ie, I);
figure
imshow(Iobr), title('Opening-by-reconstruction (Iobr)')

Iobrd = imdilate(Iobr, se);
Iobrcbr = imreconstruct(imcomplement(Iobrd), imcomplement(Iobr));
Iobrcbr = imcomplement(Iobrcbr);
figure
imshow(Iobrcbr), title('Opening-closing by reconstruction (Iobrcbr)')

fgm = imregionalmax(Iobrcbr);
figure
imshow(fgm), title('Regional maxima of opening-closing by reconstruction (fgm)')

% modify area 
I2 = I;
I2(fgm) = 255;
figure
imshow(I2), title('Regional maxima superimposed on original image (I2)')

se2 = strel(ones(10,10));
fgm2 = imclose(fgm, se2);
fgm3 = imerode(fgm2, se2);

fgm4 = bwareaopen(fgm3, 100);
I3 = I;
I3(fgm4) = 255;
figure
imshow(I3)
title('Modified regional maxima superimposed on original image (fgm4)')

% background markers

bw = im2bw(Iobrcbr, graythresh(Iobrcbr));
figure
imshow(bw), title('Thresholded opening-closing by reconstruction (bw)')

D = bwdist(bw);
DL = watershed(D);
bgm = DL == 0;
figure
imshow(bgm), title('Watershed ridge lines (bgm)')

gradmag2 = imimposemin(Gmag, bgm | fgm4);

L = watershed(gradmag2);

I4 = I;
I4(imdilate(L == 0, ones(3, 3)) | bgm | fgm4) = 255;
figure
imshow(I4)
title('Markers and object boundaries superimposed on original image (I4)')

Lrgb = label2rgb(L, 'jet', 'w', 'shuffle');
figure
imshow(Lrgb)
title('Colored watershed label matrix (Lrgb)')

figure
imshow(I)
hold on
himage = imshow(Lrgb);
himage.AlphaData = 0.3;
title('Lrgb superimposed transparently on original image')