Abstract
Seven papaya genotypes- Shahi, P020, P045, P092, Pusa Nanha, Pusa Dwarf and
CO.2 of which the first four are local genotypes and the rest are exotic, were crossed in
all possible combinations without reciprocals in a diallel fashion. It was done to know the
nature and magnitude of heterosis, obtain information on combining ability of parents and
their crosses and the pattern of inheritance of some vegetative and fruit characters in
papaya. The study was conducted at the Central Research Station of Bangladesh
Agricultural Research Institute, Gazipur during the period from September, 1993 to
March, 1996. Both positive and negative heterosis at varying levels were recorded in all
the characters under study. The highest yield heterosis was recorded in the cross Shahi
x Pusa Nanha (43.24%) over better parent followed by P092 x C0.2 (39.04%) and P045
x C0.2 (37.77%). Heterotic effect up to 26.72% was recorded in the cross Pusa Nanha
x Co.2 for total soluble solids (TSS). In respect of plant height the highest negativeheterosis was recorded in the cross P020 x Shahi (20.25%) over mid-parent.
The parents P020, Shahi and Pusa Nanha were estimated as good combiners andthe cross P020 x Pusa Nanha exhibited the highest positive sca effects followed by PusaNanha x Pusa Dwarf and Shahi x Pusa Nanha for fruit yield per plant. High gca effectsin the desirable direction for total soluble solids were shown by the parents P020, P045
and Shahi and the promising crosses were Pusa Nanha x Co.2, P092 x Co.2 and P092 x Shahi.
For plant height the parents P020, Pusa Nanha and Pusa Dwarf were identified
as good general combiners and the crosses like P020 x Shahi, P020 x C0.2 and P045 x
Pusa Dwarf were found promising for dwarfness due to significant negative sca effects.
The parent P020 was a good combiner for all the characters except fruit diameter and
flesh thickness while Pusa Nanha was a good combiner for all the characters other than
fruit length and TSS. The local variety Shahi was a good combiner for six characters
including fruit yield and TSS.
Analysis of variance for combining ability and estimates of the components of
genetic variation revealed that both additive and non-additive gene effects were significant
for almost all the characters under study. Fruit yield per plant and total soluble solids
were controlled by dominance and additive gene effects. At least four gene groups were
found to be involved in the inheritance of fruit yield per plant and the other two important
characters TSS and plant height were controlled by at least one gene group. The
heritability in narrow sense for the above three characters were 70, 61 and 69%
respectively. The Vr-Wr graphs showed wide genetic diversity among the parents.