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Question : What is supplementary pollination and how it is to be done ?
Answer :

Rice is a self pollinated crop and after anther dehiscence, there is no natural mechanism for release and wider distribution of pollen grains unlike in the cross pollinated crops. Hence for obtaining the wider distribution of pollen grains for effective pollination of CMS lines in seed production plots, the panicles of male parent at the time of anthesis are shaken mechanically. This is called supplementary pollination. It is done by vigorously shaking the panicles of male rows at the time of anthesis either with the bamboo sticks or with the help of rope held at both the ends. 4-5 times a day during 9.00 A.M. to 12.00 noon at the time of peak anthesis, for a period of 7 to 10 days. If temperatures are higher, supplementary pollination is done early around 8.00 A.M. and if temperatures are lower and weather is cloudy, it is started after 10.00 A.M. The best time to start the first supplementary pollination is 30 minutes after the dehiscence of 5-6 spikelets in the male parent.

Question : What is leaf clipping and why it is done ?
Answer :

Leaf clipping is cutting off of one third of flag leaf from the tip. Just before emergence of panicle (i.e. at booting), 1/3rd of flag leaf from the top is cut. Leaf clipping is done to facilitate cross pollination by removal of obstruction of part of leaf coming in the way of free movement of pollen grains. Percentage of out crossing and consequently seed set and seed yields are increased by leaf clipping. However, leaf clipping should not be done where BLB disease is a problem.

Question : Why GA is used in hybrid rice seed production ?
Answer :

Panicles of most of the CMS (female) lines are partially enclosed in the flag leaf and do not come out (exsert) completely from the flag leaf. About 25-30% spikelets in the panicles of female line are not exposed for pollination from the male parent. Therefore, Gibberellic Acid-3 is used in hybrid seed production primarily for better exsertion of panicle in female lines. This application also helps in better exsertion of stigma, wider opening of glumes and higher seed set.

Question : What is the recommended package for hybrid rice seed production ?
Answer :

The recommended package for hybrid seed production is as follows.

Activity

Particulars

Isolation distance

100 m. for hybrid seed production 500 m. for CMS multiplication

Seed rate

"A" line or female Parent : 15 kg/ha "B" or "R" line or male parent : 5 kg/ha

Nursery

Sparse seeding (15-20 g/m2) to ensure multi-tillered (4-5) seedlings in 25 days

Row ratio

2B: 8A for CMS multiplication
2R : 10 A for hybrid seed production

Number of seedlings/hill

2      seedlings/hill for female parent
3      seedlings/hill for male parent

Spacing

Male : Male = 30 cm Male : Female = 20 cm Female : Female = 15 cm Plant : Plant = 15 cm or 10 cm

GA3 application

60-90 g/ha in 500 litres of water at 5-10% heading in two split doses on consecutive days

Supplementary pollination

Four to Five times a day at peak anthesis with 30 minutes interval during flowering phase

Roguing

     At vegetative phase   -
     At flowering           -
     At maturity        -

Based on morphological
characters of leaf and
plant type Based on panicle characteristics Based on grain characteristics and percent seed set.

Seed yield

1.5 - 2.5 t/ha.

Question : Which are the suitable locations/seasons for hybrid rice seed production ?
Answer :

The appropriate season for large scale seed production is rabi (dry) season due to favorable weather conditions such as bright sunshine and absence of continuous rainy days during flowering period and moderate wind velocities to favour cross pollination.

The ideal locations for seed production should have well drained fertile soils with assured irrigation facilities with a mean temperature of 25-300 C, relative humidity of 70-80% and no continuous rainfall during flowering period. Large scale hybrid seed production in India is concentrated in Karimnagar & Warangal districts of Andhra Pradesh. ( seed science).

Question : Among the available hybrids, which have better grain quality ?
Answer :

Among the available released hybrids, ADTRH-1, DRRH-1 and PHB-71 have comparatively better grain and cooking quality characteristics. The hybrid Pusa RH-10 possess basmati like grain characteristics.

Question : Whether head rice recovery is lower in hybrids as compared to the varieties ?
Answer :

There are certain reports of lower head rice recovery in hybrids as compared to the varieties. Most of the presently cultivated hybrids based on the CMS line IR 58025A, possess long slender grains. When milling is done in mills primarily designed for the medium slender grains, there is more breakage of long slender grains. This problem of low head rice recovery can be overcome to a great extent, by parboiling and developing hybrids with medium slender grains.

Question : What other techniques can improve head rice recovery in hybrids ?
Answer :

For increasing the head rice recovery in presently available hybrids, harvesting is to be done at right stage. There should be proper post harvest handling. Head rice recovery can also be increased through the process of parboiling. Studies have shown that head rice recovery in hybrids could be increased by 5-6% by parboiling.

Now with the development of hybrids possessing medium slender grains in the pipeline, this problem of low head rice recovery may be overcome to a great extent.

Question : How much is the average yield advantage and net profit per hectare by cultivation of hybrids ?
Answer :

Based on the large number of demonstrations conducted in the farmers' fields during the last six years, the average yield advantage realized by the farmers over the high yielding check varieties of the regions ranged from 1.0 — 1.5 t/ha. The net profit to the farmer by cultivation of hybrids as compared to the high yielding varieties of the region ranged from Rs. 3500/- to Rs. 6000/- per hectare.

Question : Why hybrids give higher yield than varieties ?
Answer :

Hybrids give higher yield than varieties due to the phenomenon called Heterosis or Hybrid Vigour. Hybrids combine desirable features of both the parents and exhibit higher magnitude of these features including yield as compared to the parental lines. Hybrid vigour also imparts better adaptability and survival value. The higher yield obtained with rice hybrids is mainly due to higher number of spikelets and filled grains per panicle.

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