Cucurbit Genetics Cooperative Report 10:49-50 (article 28) 1987
Development of Gynoecious Lines in Muskmelon
T. A. More, V. S. Seshadri and M. B. Magdum
Division of Vegetable Crops, Indian Agricultural Research Institute, New
Delhi-110012, India
Development of true breeding gynoecious lines has led to phenomenal exploitation
of heterosis and development of hybrids in cucumber. Research on this aspect
in muskmelon has been in progress and Peterson et al. (1983) developed a
stable gynoecious line, Wisconsin 998 (WI 998).
At the Indian Agricultural Research Institute, New Delhi, three gynoecious
lines namely 86-104, 86-105, and 86-118 have been bred for true breeding
gynoecious sex. The first two lines came from a cross between a gynomonoecious
line and hermaphrodite-2 (Ac. No. 433), two of the parents were introduced
from Bulgaria and the third one came from a cross between Monoecious-1 (developed
at this Institute) and hermaphrodite-1 (EC 70674 i.e. AC No. 354). Original
crosses were made by Magdum in 1979-80 and reported in 1982. All the gynoeocious
lines in this report are in F6 generation. From F2
onwards, efforts were made to select only the pure gynoecious plant from
the segregating population and plants were maintained by layering followed
by 400 ppm silver-nitrate spray. Perfect flowers were induced after three
months of scoring for gynoecism and were increased either by selfing or
sibbing. For advancing the generations from F4 onwards, the plants
were scored for gynoecious stability for 8-10 weeks at which stage they
were sprayed with 400 ppm silver-thiosulphate (STS). This treatment induced
perfect flowers and seeds were produced. Thus, the parents were maintained
in pure gynoecious state. By this way the scoring for gynoecious stability
and maintenance was achieved in the same growing season. In later generations
the selected lines were sprayed with 400 ppm STS at two true leaf stage
and the perfect flowers were induced, which were used for perpetuation of
gynoecious stock. In this method, it was assumed that a genetically true
breeding gynoecious plant, after temporary induction of perfect phase, should
revert back to gynoecious phase again, once the effect of exogenously applied
STS has been lost.
F:C ratio and number of seeds per fruit were higher in I.A.R.I. gynoecious
lines compared with WI 998 (Table 1). All the four gynoecious lines have
to be improved for T.S.S. content, keeping in mind the consumers' preference
for sweet fruits in India. For the remaining characters, WI 998 was comparatively
better than the gynoecious lines under report.
Summing up the results, it is reported that these gynoecious lines need
further improvement for horticultural characters especially fruit weight,
shape index (preferably round) and T.S.S. content. These characters can
be improved to the desired level by further selections. It is worthy of
mention here that these lines were always scored for gynoecism from the
end of March to the middle of June when the temperatures were 40°/25°C
(day/night) and above with the prevailing long photoperiod, under field
conditions. This report brings out the possibility of developing a stable
gynoecious line in muskmelon under high temperature and long photoperiodic
conditions compared to the earlier report of Peterson et al. (1983) who
developed a stable gynoecious line under comparatively moderate environmental
glasshouse conditions.
Table 1. Mean performance of different gynoecious lines.
Average fruit weight and number of seeds/fruit were equated to
the nearest whole number.
Literature Cited
- Magdum, M. B. 1982. Studies on sex forms in muskmelon (Cucumis
melo L.). A Ph.D. thesis submitted to Post-Graduate School, Indian
Agricultural Research Institute, New Delhi, India. (Unpublished)
- Peterson, C. E., K. W. Owens, and P. R. Rowe. 1983. Wisconsin 998
muskmelon germplasm. HortScience 18(1):116.
