Dear Gitla,

I assume you are referring to a variety bred as a result of hybridising two different cultivars and developed by mass or progeny selection method, not by crossing homozygous inbred lines that produce F1 hybrids for growing like in maize.  If that is the case, bitter gourd being highly cross pollinated, there could have been intercrossing from the male parent type growing in a close-by field and segregation may have occurred. Alternately the variety may have not been selected thoroughly for uniformity. Even if yours is a F1 hybrid, outcrossing during production of hybrid seed could be the reason.

Dear Dr.Gitla Rahman

I would like to thank you for your question

I think this may be off types from out crossing.

The F1 plants must be Aa (heterozygous and homogeneous)

with best regards

Khaled

Dear Gitla, 

Out crossing must be there and male dominancy may be there because of 

Dear Gitla,

I know to little about genetic background of Bitter gourd, but in general in the F1 will be all individuals Aa. So I think there is two points:

1. how are You sure, that the parents were homozygos(I mean AA and aa). So in this case, it will posible AA Aa and aa... I for my self work with cherries, and if I crossing the same female with the same male variaties, so I get seedlings, that are different in the traits....

2. another posibility - epistasis, and I think that is more propably in You case. 

Dear Gitla,

if the number of plants having male type characters are very few then it must be off types otherwise there might be some other reasons

Hi Gitla, if you use homozygous inbred lines to generate hybrids, probably you have an outcrossing during the production of hybrid seed. You can corroborate this by molecular markers.

HI Gitla, If you are sure you have used homozygous line mean AA, aa then it could be possibility there is some out crossing with some flowers having similar character to male parent from the adjacent filed coz Bitter gourd is highly cross polinated crop or there is some epistatic effects. I think you should repeat this in controlled condition then you can find the exact reason either this is out crossing or epistasis.

Rgds

first see check points

1) self the male and female parents separately - if your getting segregation, then your parental lines are not in homozyhous condition. if your parents are homozygous all F1 population should be homozygous/ uniform.

2) in F1 pooulation all plants are showing male types fruits? if  your getting male parent fruit type (if male trait is dominant it will express in F1) but fruit shape, size, length (more than 4 genes), width all are quantitative in nature. may not expect the male type fruit.

3) F1 population how many plants /(ratio) your getting this male type fruits, if it is negligible ratio, those are off types, if considerable in ratio, then your your parents are not pure/ no control on pollination.

4) see other traits of F1 like fruit tips, curving nature,tubercules all the traits looking similar? very minor traits will also counts.