Seed Production of Vegetable, Tuber and Spice Crops (2+1)

Factors influencing seed storage

1. Biotic factors
   
2. Abiotic factors
   
1. Biotic factors
a. Factors related to seed

• Genetic make up of seed
• Initial seed quality
• Provenance
• Seed moisture content
b. Other biotic

• Insects
• Fungi
• Rodents
• Mishandling during sampling, testing
2. Abiotic factors

• Temperature
• Relative humidity
• Seed store sanitation
• Gaseous atmosphere
• Packaging material
• Seed treatment
1. a. Seed factors
1. Genetic factors

• The storage is influenced by the genetic make up of the seed. Some kinds are naturally short lived eg. Onion, Soybeans, Ground nut etc., Based on the genetic make up seeds are classified into
• Micro biotic – short lived
• Meso biotic- medium lived
• Macro biotic – long lived
Initial seed quality

• Barton (1941) found that the seeds of high initial viability are much more resistant to unfavourable storage environmental conditions than low viable seed. Once seed start to deteriorate it proceeds rapidly. The seed which injured mechanically suffered a lot and loses its viability and vigour very quickly. Generally small seeds escape injury whereas large seeds are more likely to be extensively damaged eg., bean, lima-bean and soybean. Spherical seeds usually give more protection than flat or irregularly shaped seeds.
Effect of provenance

• The place where the seed crop was produced greatly influences the storability.
• eg., Red clover seeds grown in Canada stored for 4 years with 80 per cent germination whereas, seeds grown in England and New Zealand stored only for 3 years with per cent germination. This is due to different climatic conditions and soil types prevailing in different places.
Effect of weather

• Fluctuating temperature during seed formation and maturity will affect seed storage. Pre-harvest rain may also affect the viability.
Pre harvest sanitation spray

• In pulses, insect infestation comes from field eg., bruchids.
Seed moisture content

• Most important factor influences the storability. The amount of moisture in the seeds is the most important factor influencing seed viability during storage.
• Generally if the seed moisture content increases storage life decreases. If seeds are kept at high moisture content the losses could be very rapid due to mould growth very low moisture content below 4% may also damage seeds due to extreme desiccation or cause hard seededness in some crops.
• Since the life of a seed largely revolves around its moisture content it is necessary to dry seeds to safe moisture contents. The sage moisture content however depends upon storage length, type of storage structure, kind / variety of seed type of packing material used. For cereals in ordinary storage conditions for 12-18 months, seed drying up to 10% moisture content appears quite satisfactory. However, for storage in sealed containers drying upto 5-8 % moisture content depending upon particular kind may be necessary.
Classification seed based on moisture content and storability
Orthodox

• The seeds able to tolerate moisture loss and less seed moisture favours the storage i.e., decreased moisture increased storage period. Eg. Rice, sorghum and most of the cultivated species.
Recalcitrant

• Just opposite to the orthodox. Seeds not able to tolerate moisture loss. Required high moisture for viability maintenance.
Microflora, Insects and Mites

• The activity of all these organisms can lead to damage resulting in loss of viability. The microflora activity is controlled by Relative Humidity temperature and Moisture Content of seed.
• Treated seeds with fungicides can be stored for longer periods.
• Fumigation to control insects will also help to store longer period.
• Fumigants - eg., methyl bromide, hydrogen cyanide, ethyline dichloride, carbon tetra chloride, carbon disulphide and napthalene and aluminimum phosphine.
2. Abiotic factors
Relative humidity

• Relative humidity is the amount of H2O present in the air at a given temperature in proportion to its maximum water holding capacity. Relative Humidity and temperature are the most important factors determining the storage life of seeds. Seeds attain specific and characteristic moisture content when subjected to given levels of atmospheric humidity. This characteristic moisture content called equilibrium moisture content.
• Equilibrium moisture content for a particular kind of seed at a given Relative Humidity tends to increase as temperature decreases. Thus the maintenance of seed moisture content during storage is a function of relative humidity and to a lesser extent of temperature. At equilibrium moisture content there is no net gain or loss in seed moisture content.
Temperature

• Temperature also plays an important role in life of seed. Insects and moulds increase as temperature increases. The higher the moisture content of the seeds the more they are adversely affected by temperature. Decreasing temperature and seed moisture is an effective means of maintaining seed quality in storage.
Gas during storage

• Increase in O2 pressure decrease the period of viability. N2 and CO2 atmosphere will increase the storage life of seeds.