HYBRID SEED PRODUCTION IN MAIZE.pdf
- 1. SEED SCIENCE & TECHNOLOGY HYBRID SEED PRODUCTION IN MAIZE Dr. K. Vanangamudi Formerly Dean (Agriculture), TNAU, Coimbatore. Dean, Adhiparasakthi Agricultural College, Professor & Head, Seed Science & Technology, TNAU, Coimbatore. Crossing technique: Manual emasculation by detasseling Detasseling: Removal of male inflorescence from the monoecious crop Time for detasseling: Shedding of pollen from tassel in 1-2 days after emergence. Detasseling Removal of tassel from female parent. Done when tassels emerged out of boot leaf, but before anthesis have shed pollen. Anthers take 2 - 4 days to dehisce after complete emergence. Only in few cases, anthers start dehisces before its complete emergence. In such case, detasseling should be done earlier. Detasseling is done every day from the emergence of tassel upto 14 days. Method Hold stem below boot leaf in left hand and base of the basal in right hand and pull it out in a single pull. Grasp entire tassel so that all the pollen parts are fully removed. Do not break or remove leaves as removal will reduce yields and will result in lower quality of seed.
- 2. Improper detasseling: A portion of the tassel is remaining in the plant while detasseling. Immature detasseling: Carrying out detasseling work when the tassel is within the leaves. Incomplete detasseling: Tassel is remaining in lower or unseen or unaccounted in within the whole of leaves. There should not be any shedding tassel. Shedding tassel: Either full or part of tassel remain in female line after detasseling and may contaminate the genetic purity of the crop.
- 3. System of Hybrid seed production Detasseling (Manual creation of male sterility ) Types of hybrids Single cross hybrid Cross between 2 inbreds A genotype will be detasseled and crossed with B genotypes COH 1- UMI 29 x UMI 51 COH 2- UMI 810 x UMI 90 CoH(M) 5-UMI 285 X UMI 61 Double cross Cross between two single crosses. Cross between 2 hybrids (A x B) x (C x D). (A x B) single cross hybrid will be produced by detasseling A and by crossing with B (C x D) hybrid will be produced by detasseling C and crossing with D. Then (A x B) will be detasseled and crossed with (C x D) hybrid.
- 4. Example Ganga 2: (CM 109 x CM 110) x (CM 202 x CM 111) Ganga 101: (CM 103 x CM 104) x (CM 201 x CM 206) COH3: ( UMI 101 x UMI 130 ) x (UMI 90 x UMI 285 ) Three way cross Cross between a single cross and an inbred. First generation resulting from the crossing of on approved inbred line and a certified open pollinated variety A x variety A will be detasseled and allowed for crossing in the variety. Example Ganga - 5: (CM 202 x CM 111) x CM 500. COH (M) 4: (UMI 90 x UMI 285) x UMI 112 Double top crosses The first generation resulting from the controlled crossing of a certified single cross and a certified open pollinated variety.
- 5. (A x B) x variety (Ax B) will be detasseled and crossed with a variety Seed production technology Season - November- December, Mid July, Jan, Feb and Sep. Oct Isolation distance Foundation seed (m) Certified seed (m) 1. Inbreds 400 - 2. Single cross hybrid 400 - Field standards for isolation (modification based on situation) For (foundation single crosses and hybrid of certified class) Foundation stage Certified stage Same kernal color 400 200 Different kernal colour 600 300 Field of single cross / inbreds not confirming to varietal purity 400 200 Single cross with same male parent confirming to varietal purity 5 5 Single cross with other male parent not confirming to varietal purity 400 200 In hybrid seed production (certified seed stage) alone, the isolation distance (less than 200 meter) can be modified by increasing the border rows of male parent, if the kernal colour and texture of the contaminant are the same as that of the seed parent. Determined by the size of the field and its distance from the contaminant as shown below. Area (ha) Isolation distance (m) Border rows < 4 ha 200 1 < 4 ha 150 5 < 4 ha 100 9 < 4 ha 50 13 10-12 ha 180 1 10-12 ha 130 5
- 6. 10-12 ha 80 9 10-12 ha 30 13 > 16 ha 165 1 > 16 ha 115 5 > 16 ha 65 9 > 16 ha 15 13 Spacing Seeds are sown in ridges and furrows Hybrids: 60x 25 cm Seed rate: Female : 7-10 kg ha-1 Male: 3 - 4 kg ha-1 Spacing: Female: 60 x 20 to 75 x 30 cm Male: 45 x 30 cm Planting ratio Single cross: 4:2 Double cross: 6:2 3 way cross: 6:2 Border rows a. Inbreds & single cross - 4 rows b. Others - 3 rows
- 7. Fertilizer NPK kg / ha : 200 : 100 : 100 Basal : 100: 100: 50 1st Top : 50: 0: 0 (20th days -vegetative phase) 2nd Top : 50: 0: 50 (Boot leaf stage at 45 days) Foliar : DAP 2% at 50% flowering In Zn deficient soil : ZnSO4 @ 25 kg ha-1 Roguing Shedding tassels are to be removed in roguing. Refers to the tassels in female parent rows, shedding pollen or that has shed pollen in hybrid maize plots. Field standard (%) FS CS Off types: 0.2 0.5 Shedding tassel: 0.5 1.0 (when receptive silk is 5% or more) Inseparable other crop: Nil (both stage) Objectionable weed: Nil (both stage) Designated diseases: Nil (both stage) Field standards –specific Specific factors Certified stage Off types shedding pollen when 5 % or more of seed parent in receptive silk 0.50 % Seed parent shedding pollen when 5 % of the seed parent is having receptive silk 1.0 % Total of pollen shedding tassel including tassel that had shed pollen for all 3 inspections conducted during flowering on different dates 2 .0 % Off types in seed parent at final inspection 0 .5 % Number of inspection: Four (Seed certification officers) One: Before flowering Three: During flowering
- 8. Harvest Harvest when the moisture content falls to 20-25%. Harvest male first and remove from the field and then harvest female. Threshing Dehusking - Husks are removed manually. Cob sorting - Remove ill filled, diseased cobs and cobs having kernel colour variation. Zenia Direct/visible effects of pollen on endosperm and related tissues in the formation of a seed colour. E.g. seed colour. In maize, gene present in sperm cell contributes in expression of colour of hybrid seeds. Metazenia Effect of pollen on the maternal tissues of fruit Shelling Cob sorting should be the first operation it is a post harvest, evaluation for genetic purity. Sheath is removed and check for kernel colour, shank colour, diseased cobs and kernel arrangement. Cobs are shelled either mechanically or manually at 15-18% moisture content. Improper shelling leads to 48% damage to kernel Crack on pericarp can be identified by FeCl3 or Tz test. Shelling is done mechanically using cob sheller and manually by rubbing with stones. Drying Seeds are dried to 12% moisture content. Seed treatment Slurry treat the seeds with 8% moisture content either with captan or thiram 75% W.P. @ 70 g/100 kg with 0.5 litre of water. Treated seeds can be stored for 1 year in cloth bag. Others: As in varietal seed production Seed yield: 2.5 - 3.6 t/ha
- 9. Seed standard Factor Maximum permitted (%) Physical purity minimum 98.0% Inert matter maximum 2.0% Other crop seeds maximum 10.0/kg Other distinguishable varieties (maximum) 10.0/kg (Number) Weed seeds basal on kernel colour and texture Nil Germination (minimum) 90.0 Moisture (%) (maximum) For moisture vapour pervious 12.0% For moisture vapour poof containers (maximum) 8.0%