Training Manual Development Of Cultivars And Seed ... - icrisat

It is important, as indicated earlier, that the hybrid parents should 'nick' in their flowering when
sown simultaneously. Further, information on the flowering behavior of the hybrid parents is useful in
deciding the sowing dates of the isolation involved for hybrid seed production. Also, care should be taken
to ensure that the seed develops and matures during a period when it does not rain and when relative
humidity in the air does not exceed 5 0 % .
It is difficult to predict the flowering time of the parents accurately, because many A- and R-lines
interact with temperature and day length. The interactions cannot be predicted (day length can be
calculated for a given location, but temperature cannot be predicted). So it is always advisable to stagger
the sowing of R-lines, especially when they are known to flower earlier than the A-lines. For example,
if the male parent is known to take 62 days to 5 0 % flowering at a given location and the A-line 72 days,
the male parent has to be sown 13-15 days after sowing the A-line. Pollen shedding from the R-line
usually lasts 10-15 days. Transplanting the plants either in strips in each row or all plants in one of the
two rows in the R-line is known to delay flowering by 8-10 days and thus increase the period of pollen
availability; this leads to higher seed-setting on the A-line.
It is important that roguing of off-types should be done regularly before and during anthesis in both
the A- and R-lines. Also, monitoring for pollen shedders in the A-line and removing them should be done
without fail during anthesis. All possible precautions should be taken against seed contamination through
mechanical mixing during harvesting and threshing. It is recommended that the R-line should be
harvested first and removed from the field and yard before starting the harvest of the hybrid seed.
Further, the following precautions will enhance seed production:
• Selection of a field with good fertility and appropriate previous crop, preferably a legume, will be
useful in achieving higher productivity of seed with good quality.
• Monitor flower-bud development 20-30 days after sowing. Differences in the time of initiation and
size of panicle initially in the A- and R-lines would indicate differences in their time of 5 0 %
flowering; so hasten flowering by selective irrigation and/or application of nitrogenous fertilizers
such as urea or ammonium sulphate.
• Follow uniform crop management practices to grow a good crop across the entire isolation.
• Follow plant-protection measures and control pests and diseases because differential
susceptibility in the parents may lead to asynchronous flowering (Murty et al. 1994).
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