Seed Health Management for Better Productivity - Govind Ballabh ...

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(Seed Health Management for Better Productivity)the seed quality assurance. Different methods can be used to enhance seeds and seedlingperformances namelyi) Film-coating methods: It allows the chemicals to be applied in a synthetic polymer that issprayed onto the seeds and provide a solid, thin coat covering them. The advantage of thepolymers is that they adhere tightly to the seed and prevent loss of active materials like fungicides,nutrients, colorants or plant hormones. Some novel applications of film coating are used to modifyimbibitions and germination. They can confer temperature-sensitive water permeability to seeds oraffect gaseous exchange. By this they control the timing of seed germination and seedlingemergence.ii) Seed pelleting methods: This adds thicker artificial coverings to seeds, which can be used tocover irregular seed shapes and add chemicals to the pellet matrix, e.g. of sugar beet or vegetableseeds. The pellet matrix consists of filling materials and glue. Loam, starch, tyllose (cellulosederivative) or polyacrylate/polyacrylamide polymers are commercially used. Seed pelleting is alsoused to increase the size of very small horticultural seeds. This provides improved plantingfeatures, e.g. singulate planting, the use of planting machines, or precise placement and visibilityin/on the soil.iii) Seed Priming methods: It is the most important physiological seed enhancement method.Seed priming is a hydration treatment that allows controlled imbibition and induction of the pregerminativemetabolism ("activation"), but radicle emergence is prevented. The hydrationtreatment is stopped before desiccation tolerance is lost. An important problem is to stop thepriming process in the right moment; this time depends on the species and the seed batch.Molecular marker can be used to control the priming process. Priming solutions can besupplemented with plant hormones or beneficial microorganisms. The seeds can be dried back forstorage, distribution and planting. Germination speed and synchrony of primed seeds areenhanced and can be interpreted in the way that priming increases seed vigor. A widertemperature range for germination, release of dormancy and faster emergence of uniformseedlings is achieved. This leads to better crop stands and higher yields. A practical drawback ofprimed seeds is often a decrease in storability and the need for cool storage temperatures.Several types of priming viz. Osmopriming, Hydropriming and Matrixpriming are commonly used.i) Osmopriming (osmoconditioning) is the standard priming technique. Seeds are incubated inwell aerated solutions with a low water potential, and afterwards washes and dried. The low waterpotential of the solutions can be achieved by adding osmotica like mannitol, polyethyleneglycol(PEG) or salts like KCl.ii) Hydropriming (drum priming) is achieved by continuous or successive addition of a limitedamount of water to the seeds. A drum is used for this purpose and the water can also be appliedby humid air. 'On-farm steeping' is the cheep and useful technique that is practiced by incubatingseeds (cereals, legumes) for a limited time in warm water.- 190 -
(Seed Health Management for Better Productivity)iii) Matrixpriming (matriconditioning) is the incubation of seeds in a solid, insoluble matrix(vermiculite, diatomaceous earth, cross-linked highly water-absorbent polymers) with a limitedamount of water. This method confers a slow imbibition.Hybrid seeds production:The contribution of agriculture to the national economy has been constantly declining45.2% to 21% during 2005-06 in India. The challenge is to increase productivity in the scenario ofreducing/ stagnant resources of land and water, and significant losses due to several biotic andabiotic stresses. Hybrid seed technology can contribute to the overall productivity once usedjudiciously.The successful development and use of hybrid rice technology in china during 1970’s ledthe way for development and release of rice hybrid varieties elsewhere. India has made goodprogress in this regard and numbers of hybrid varieties of rice are being used by the farmers.Hybrid-rice can be produced in the following ways.1. Three-line system: The hybrid seed production involves multiplication of cytoplasmicgeneticmale sterile line(A line), maintainer line (B line) and a restorer line (R line); andproduction of F1 hybrid seed (AxR)2. Two-line system: The hybrid seed production involves the use of photo-period sensitivegenetic male steriles (PSMS). Any normal line can serve as a restorer.3. By using chemical emasculators: Chemicals that can sterilize the stamen, with little or noeffect on the normal functioning of the pistil, can be used to emasculate female parents forhybrid rice production. The advantages are obvious, no special development of malesterile or restorer lines is required, and extensive varietal resources are available.Chemical emasculators such as male gametocie 1(MF1) and male gametocie 2(MG2) weredeveloped in China and have been successfully used in hybrid rice production. In chemicalemascultion, physiological male sterility is artificially created by spraying the rice plant withchemicals to induce stamen sterility without harming the pistil. In hybrid seed production,two varieties are planted in alternate strips, and one is chemically sterilized and pollinatedby the other.Artificial seeds production:Cell culture and regeneration techniques allow the mass production of somatic embryos,which can subsequently be packed in a suitable gel-type matrix (agar- agar, gums, dextrans) andcovered with artificial seed coat and are referred as artificial seeds. This can be used to generategenetically identical seedlings of poplar, orchids and other species. Further it can be used as animportant packaging system.Biotechnological interventions in quality seed productionAlthough conventional plant breeding methods have led to development of crop varietieswhich eventually resulted in sustained increase in crop productivity, they are now superseded byselection procedures based on modern biotechnological tools such as marker assisted selection- 191 -
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Page 219 and 220: potential. An improvement in qualit
Page 221 and 222: 9. Session Arrangement CommitteeDr.
Page 223 and 224: 9. Dr. Pradip Kumar BorahSr. Scient
Page 225 and 226: TRAININGONANNEXURE-IIISEED HEALTH M
Page 227 and 228: ANNEXURE-IVCENTRE OF ADVANCED STUDI
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