growth stages of wheat

it explains brief information on phenological studies at different growth stages of wheat

1. UNIVERSITY OF AGRICULTURAL SCIENCES DHARWAD Course title: Agronomy of major cereals and millets [AGR-506] (2+1) Presentation topic:- Phenological studies at different growth stages of wheat Submitted by:- Suresh Jambagi Sr. MSc(Agri),Entomology PGS18AGR7711

2. WHEAT Genus- Triticum Family- Gramineae Origin= Mediterranean region or S-W Asia (Turkey) C3, Long day plant. First cultivated around 9600 BC. Cultivated wheat Triticum aestivum is an allohexaploid (2n=6x=42). Staple food of about 35% of world population. Contains spongy protein i.e Gluten (colloidal complex of gliadine and glutenin ) essential for baking Considered as ‘Versatile cereal food’. Area Production WORLD 222.68Mha 756MT INDIA 30.79Mha 98.51MT KARNATAKA 1.74 Lakh ha 1.56 Lakh tons

3. Classification Diploid wheat (2n)= 14 chromosomes Tetraploid wheat (2n)= 28 chromosomes Hexaploid wheat (2n)= 42 chromosomes 1. Einkorn wheat (2n=14) – Triticum monococcum (cultivated) 2. Emmer/ Khapli wheat (2n=28) – Triticum dicoccum (cultivated) Triticum dicoccoides (wild) 3. Durum/Macaroni wheat (2n= 28)- Triticum durum 4. Bread wheat (2n=42)- Triticum aestivum

4. GROWTH STAGES OF WHEAT I. Pre-establishment stages Pre-emergence- Germination of seeds, which produces seminal roots and coleoptiles. Emergence- Germinating seeds produce coleoptile above the soil surface. II. Vegetative stages 3. Seedling- Young plants establish larger root systems in their seedling stage. 4. Crown root stage- This coincides with three/four leaf stage of plant. 5. Tillering - Plant produces crown and branch out into tillers from their base at soil surface. 6. Jointing- At this stage, the plants starts elongating when the nodes start developing above the crown node.

5. III. Reproductive stages 7. Booting- The upper most leaf swells out into flag holding the spike into it. 8. Heading- The spike starts emerging out from the leaf sheath. 9. Flowering- Anthesis of florets and fertilisation of ovaries take place. IV. Post-anthesis stage 10. Filling- After fertilisation, the ovaries start elongating in ovules or seed passing through milk, soft dough and hard dough stages. 11.Maturity- At this stage, the colour of glumes changes and kernels become fairly hard. 12.Harvest

6. Growth stages of winter wheat ( Waldren and Flowerday , 1979 Growth stage Description Emergence of coleoptile 1 Crown is visible, tillers develop 2 Leaf sheaths elongate and forms a false stem 3 Culm elongation . First internode visible (jointing) 4 Top of flag leaf visible (Boot stage) 5 Peduncle elongates . Inflorescence emerges (heading) 6 Flowering (anthesis) 7 Anthesis complete. Grain filling begins, lower leaves change colour 8 Grain is stiff dough. Flag leaf has lost green colour 9 Ripening . Grains hard but will not crack. Inflorescence lost green colour . Uppermost node still green 10 Maturity . Grain cracks and is easily separated from chaff.

7. Phenology of wheat: Organ differentiation defines the various stages of wheat development. Physiologically, the stages are usually distinguished as germination, emergence, tillering , floral initiation or double ridge, terminal spikelet, first node or beginning of stem elongation, boot, spike emergence, anthesis and maturity. These stages may be grouped into: 1. germination to emergence (E); 2. growth stage 1 (GS1) from emergence to double ridge. 3. growth stage 2 (GS2) from double ridge to anthesis. 4. growth stage 3 (GS3), includes the grain filling period, from anthesis to maturity. NOTE: * The time-span of each development phase essentially depends on genotype, temperature, day-length and sowing date. * Physiological maturity= The time when the flag leaf and spikes turn yellow ( Hanft and Wych , 1982).

8. I . Germination to emergence The minimum water content required in the grain for wheat germination is 35 to 45 percent by weight. Germination may occur between 4° and 37°C, optimal temperature being from 12° to 25°C. Seed size does not alter germination but affects growth, development and yield. Bigger seeds have several advantages when compared to smaller seeds, such as faster seedling growth, higher number of fertile tillers per plant and higher grain yield. During germination, the seminal roots grow first , followed by the coleoptile, which protects the emergence of the first leaf. The length of the coleoptile limits sowing depth, and its length changes with genotype, increasing only slightly when seeds are sown deeper. Semi-dwarf wheat has shorter coleoptiles than tall wheat.

9. II. Emergence to double ridge (GS-I) Floral initiation (double ridge) occurs at 20 DAS in spring wheat and 35 DAS in winter wheat The duration of this stage (GS1) may vary from 60 to 150 days depending on sowing date and genotype. Wheat tillers grow from the axils of the main shoot leaves. The potential number of tillers varies with genotype, particularly among flowering types. winter types having a greater number. Semi dwarf wheats usually have a high number of tillers. Bud differentiation into tillers and tiller appearance generally end just before stem elongation starts. Tillering does not end at any specific wheat development stage, but rather it is controlled by a number of genetic and environmental factors. Longnecker  et al.(1993). Not all tillers produce spikes in wheat, and many tillers abort before anthesis. The number of productive tillers depends on genotype and environment and is strongly influenced by planting density. Under favourable conditions, one and one-half fertile tillers per plant is a usual number.

10. III. Double ridge to anthesis Wheat plants have 4 to 6 leaves in the main shoot when the growing apex changes from the vegetative to the reproductive stage. The glume and lemma primordium stages follow. The floret primordia are found in the axil of each lemma. Temperatures above 30°C during floret formation cause complete sterility. Each spikelet has 8 to 12 floret primordia in the central part of the spike. The basal and distal spikelets have 6 to 8 florets. Less than half of these florets complete anthesis; the rest abort or are insufficiently developed before anthesis to be fertilized.

11. IV. Anthesis to physiological maturity The wheat spike contains only one spikelet per rachis node. Each spikelet has 3 to 6 potentially fertile florets, which are self-pollinated in 96 percent of the cases. Anthesis begins in the central part of the spike and continues towards the basal and apical parts during a 3 to 5 day period. The proximal florets of the central spikelet are fertilized 2 to 4 days earlier than the distal florets. These grains usually have a greater weight. After floret fertilization, cellular division is rapid, during which the endosperm cells and amyloplasts are formed. This period is known as the lag phase and lasts for about 20 to 30 percent of the grainfilling period. After there is a phase of cell growth, and differentiation and starch deposition in the endosperm, which corresponds to linear grain growth and takes from 50 to 70 percent of the grainfilling period. The embryo is formed at the time of endosperm growth.

12. Days from emergence to physiological maturity in a spring and winter wheat Development stage Time (days) Spring wheat Winter wheat Emergence Floral initiation (double ridge) 20 35 Terminal spikelet 45 60 First node 60 80 Heading 90 120 Anthesis 100 130 Physiological maturity 140 170

13. Wheat needs Cool and moist weather –Vegetative period Warm and dry weather – Reproductive stage Vernalisation Vernalisation is the requirement to be exposed to cold temperatures in order for the reproductive phase to begin. Temperatures in the order of 1° – 12° C are needed to meet this requirement depending on varietal characteristics. Wheat varieties that have little or no vernalisation requirement are often referred to as spring types , and temperatures in the range of 7 to 18° C for brief periods will be sufficient for vernalisation . Wheats that have a strong vernalisation requirements are called winter types , and lower temperatures of between 0° and 7° C for several weeks are needed for vernalisation . Vernalisation is a useful tool in that it gives an environmental cue to the plant on when is the most suitable time to transform to the reproductive phase , and so offer a greater sowing window.

14. REFERENCES:- Agronomy of field crops – S R Reddy, Y. Reddi Ramu Modern techniques of raising field crops – Chidda singh , Prem singh , Rajbir singh Botany of field crops- J.S Nanda and P.K Agarwal websites

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