The first generation progeny of cross between two genetically diversified parents is called hybrid (seed) and the whole procedure of seed production is called hybrid seed production.
Diagram 1: Represent how the hybrid seed produced by crossing between A x B.
Agronomic Approaches for Hybrid Seed Production:
Different strategies are adopted for hybrid seed production which are given below:
- Site selection
- Isolation distance
- Fertilizer requirement
- Raising of parental lines
- Plant protection measures
- Irrigation scheduling
- Physiological disorders
- Site selection:
Medium to heavy deep well drained soil is considered ideal for seed production in cotton.
- Isolation distance:
Maintenance of genetic purity for certified seed production of male sterility based hybrids depends upon proper creation of isolation distance. For cotton hybrid seed production plot should have 30 m isolation distance from all sides from all other fields. The isolation distance between parents should be minimum of 5 m.
- Fertilizer requirement:
Fertilizer dose of 100: 50: 50 or 150: 75: 75 kg/ha NPK depends upon soil fertility, out of which 50: 50: 50 or 75: 75: 75 NPK as basal dose and remaining 50 or 75 (N) is applied in two splits as at starting of square formation and at boll development.
- Raising of parent lines:
If male sterile lines are used as parent’s lines then following steps or rules are adopted for raising of parental lines, which are given below:
- Inbred line should be approved by certified agency.
- It should be the progeny of 2 approved inbred lines of which one is male sterile.
- Inbred line should be true breeding strain resulting from self-pollination with selection.
- A male sterile line should contain cytoplasmic genetic male sterility which shed no viable pollens, maintain by normal sister strains which are used as pollinators.
The sowing date of parental lines are so adjusted there is a synchronization of flowering in females and male parent and there will continuously supply of pollen till crossing season is over. Staggered planting of male done depending on date of flowering in male and female.
- Plant protection measures:
Attack of sucking pest is controlled by confidor @ 100 ml/ha. Boll worm attack on flowers and squares are manage by spraying endosulphan @ 2L/ha.
For control of pink boll worm attack, spray of thiodecarb @ 1 kg /ha.
Bacterial disease is control by Bavistin @10g/ 10 litre water.
- Irrigation scheduling:
By the use of alternate furrow method, irrigation is done whenever required.
- Physiological disorder:
Leaf reddening, potassium deficiency and boll shedding are the major disorders related to the physiology of hybrid.
Foliar spay of 2% DAP solution, 2%urea solution are used to overcome the reddening problem, whereas foliar spray of 1% potassium chloride solution is sprayed during flowering to maintain potassium deficiency.
Application of auxins @ 10 ppm prove helpful for better fruit set and increase yield.
Pick that bolls which are completely opened, collect in proper bags.
Clean and stored in gunny bags with proper tagging. Under developed and damaged bolls should be removed and the remaining should be sent for ginning purpose and finally hand over to seed certification.
STEPS INVOLVE IN HYBRID SEED PRODUCTION:
Emasculation of female parent by following methods:
- Doak method
- Pinching off of top of corolla
- Straw tube
- Petal remove
For emasculation there is highly skilled labour is required. different emasculation methods are used which are described below:
- Doak method /thumb nail method:
Successful method used in hybrid seed production of tetraploid cotton. This method is involving removal of corolla along with anther sheath by giving shallow cut at the base with thumb nail and removing corolla and anther column in one jerk twisting action.
- Pinching off of top of corolla:
Such method is used for emasculation of diploid flowers where flower top bud is pinched loss using thumb nail and first finger nails by hand so that stigma tip get slightly exposed and bud is covered with mud, as bud matures, the stigma tip extend sufficiently for enabling pollination.
- Straw tube method:
The top of corolla of bud is pinched off and a piece of straw is used by inserting it into style to separate all anthers from anther column and leaving the tube in same position and pollen is applied to next morning.
- Petal remove and brushing off anthers:
Petals are removed by thumb nail, anthers brushed off by the lightly touching and moving thumb on stamina column. This method is useful for herbaceous type of cotton buds because anthers are granule shape and easily removable.
FACTORS AFFECTING YIELD AND QUALITY OF HYBRID:
- Male female ratio
- of male flowers for pollinating proper female plants.
- Staggering sowing pattern of parent plants for better chance of pollination
- Stage and period of crossing
- Vigor of female parental seed.
- Pollen production ability of male parent
- Position of boll set on the plant
ECONOMICS OF HYBRID SEED PRODUCTION:
Different crucial expenditures are involved in the production of hybrid seed as given below:
- Land lease
- Cost on preparatory tillage
- Cost on parental seed purchasing
- Sowing cost
- Inspection charges
- Cost of fertilizer
- Roughing off
- Irrigation charges
- Plant protection measures
- Emasculation efficiency
- Pollination efficiency
- Picking of crossed bolls
- Storage carefully
- Transport to gin
- Ginning charges
- Packing charges
HONEY BEES AS A POLLINATORS IN HYBRID SEED PRODUCTION:
Insects such as (Apis mellifera) honey bees are the major pollinators.
Honey bee visit on cotton flowers according to
- Day hours
- Temperature severity
50 pollen grains per stigma are enough to fertilize all ovules, an average 10 bees / 100 cotton flowers are enough practically coat all stigma with pollen. Sucrose is an important source show positively relation with honey bee visit as high sucrose content is directly proportional to the visit of honey bees on cotton flowers.
SEED STANDARDS FOR CERTIFIED HYBRID SEED OF COTTON:
|Pure seed (min.)||98.0 %|
|Other crop seed||10/kg|
|Germination %||70 %|
Written by .
Muhammad Umair Yasin*1, Hina Ahmed Malik2.
1Department of Agronomy, University of Agriculture, Faisalabad, Pakistan.
2Soil Agriculture Research Center Lab D-138, Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan.
*Corresponding author’s email: firstname.lastname@example.org