Harmful seed-borne plant pathogens (present in/on the seed), can be the source of infection on the crops that originated from infected seeds.

The use of healthy seed is therefore a very important tool for the success of the crop. Seed treatment aims at reducing/inactivating the inoculum of seed-borne pathogens or indirectly improve plant defence response using a mechanism known as biopriming.

In organic farming, where chemical solutions cannot be applied, products based on microbial consortia (MCs) and natural compounds (NCs) are currently being studied as sustainable alternative.

In order to preserve their activity, products containing MCs and NCs need to be stored using correct procedures normally provided by the manufacturer.

In fact, MCs and NCs are natural ingredients which are normally in nature and are susceptible to temperature, humidity, oxidation and UV exposure. Once opened, products should be used rapidly as oxygen will interact with NCs and promote MCs growth. If the products derived from NCs are usually stable, the MCs must be stored away from extreme temperatures (optimal range 10-30°C).

When using compounds such as MCs and NCs for an application on seeds, products should be diluted in water, at the doses recommended by the manufacturer.

Seed dressing should be carried out by soaking the seeds in the MC suspension/NC solution.

The recommended volume used is about 10 times the volume of seeds, in order to completely cover them.

After 10 minutes shaking to ensure a uniform distribution, the seeds need to be left to dry on absorbent paper.

It is recommended to sow the seeds within 24 hours of the seed dressing in order to maintain unaltered the NCs characteristics and MCs vitality during the first stages of germination.

Black bean aphid - Aphis fabae Scop. is a polyphagous specie, attacking over 200 plant species: ornamental shrubs represent primary hosts and herbaceous plants (celery for seed production, spinach, beans, corn, poppy, sugar beet, etc.) are secondary hosts. The black bean aphid is a small insect, 1.6 – 2.5 mm, black and soft-body. The insect sucks sap from leaves and form colonies on shoots, flowers, pods and on the underside of leaves. Due to the attack, the leaves are wrinkled, discolored and dry, and the pods remain small and give low yields. For seed crops, the pest is dangerous because it is the vector of some viruses, in beans, beet, etc.

Control

• Remove of the host weeds to diminish the biological reserve of the pest.

• Attracting species of parasites: Aphelinus sp., Praon dorsale Hal., Lisiphlebus fabarum Marsh., L. ambiguus Hal., Trioxys angelicae Hal.; predators: Coccinele septempunctata L., Hippodamia variegata L., Adalia bipunctata L., Syrphus sp., Leucopis griseola T., Chrysopa carnea Steph. C. pearla L. by cultivation of Umbelliferae and Compositae plants as sources of food and refuge places in hot days for useful fauna.

• Application of treatments with repellent products: extracts fermented by Artemisia absinthium, Urtica dioica, dolomite dust, ash.

• Application of treatments by spraying or dusting with botanical insecticides: neem, piretrins, rotenon, Quassia extract. If the attack is small, the treatments can be made localized, only on the attacked plants. If the attack is generalized, the treatments will be performed all over the surface.

• Application of treatments by spraying or dusting with biological insecticides based on entomopathogenic agents: Entomophthora aphidis Hoffm., E. fresnei Now., Cladosporium sp.

The high germination percentages of the seed samples and the growth of the derived plantlets are the main criteria to assess the quality of seed batches. The seed quality can be evaluated by seed germination tests. In the Council Directive 2002/55/EC of 13 June 2002 on the marketing of vegetable seed is defined that cauliflower and broccoli seeds being sold must exhibit at least 70 % and 75 % germination percentages, respectively.

To test the germination percentage of small seed lots, a simple method can be performed to test their quality.

Fifty seeds will be placed in three aluminum takeaway containers on absorbent paper which will be watered by distilled water without any flooding.

The seeds will be covered by absorbent paper and the alluminium containers will be placed at room temperature and in dark conditions (optimal temperature 20°C). Seedling assessment takes place at the cotyledon disclosure when the first true leaf appears.

Each day after sowing the number of germinated seeds will be registered and seedlings will be removed afterwards. After 12 days calculate the germinability (percentage of seeds providing seedlings in comparison to the total number of seeds) and the germination time (days) of the seed lots.

Common blight produced by Xanthomonas campestris pv. phaseoli is very important disease of bean culture in many regions of the world. Damages are very high losses of production can be between 25 to 60%. The bacterium is transmitted year by year through the infected seeds. Xanthomonas can survive over 15 years in seed and infect the bean plant in vegetation period. Throughout the vegetation, bacteria can be spread by humans, farm implements, insects, wind, rains or hail. The disease occurs on all air organs.

The main sympthoms are small, water-soaked areas that enlarge and become encircled by a comparatively narrow zone of lemon-yellow tissue. These lesions turn brown, the leaf rapidly becomes necrotic and defoliation may result. The stem surface often splits, releasing a yellow bacterial exudate (in halo blight infections, exudates are light cream or silver colored).

Controlling Common blight in organic bean

• Use certified seed of bean from organic agriculture.

• Bean seeds solarization after harvesting by sun exposure 6 - 8 hours (non-chemical environmentally friendly method for controlling diseases, using solar power to increase the seeds temperature to levels at bacteria will be killed or greatly weakened them infections).

• Choose local varieties less susceptible to common bacterial diseases.

• Avoid overhead irrigation where possible.

• Avoid working in fields when plants are wet.

• Incorporate infested bean debris into the soil after harvest.

• Rotate beans with non-host crops such as small grains for at least three-four years.

• Good sanitation by remove diseased plants or weeds from the field.

• Applying 2 - 3 treatments with Bordeaux mixture.

Harvest and clean the fruits, and slice them longitudinally. Crush the fruit sections into a mixture of

pulp, seeds, and juice. Subsequently pour the mixture into a large container where it ferments for a

period usually lasting three days. For acid extraction, apply an equal volume solution of hydrochloric

acid (HCl) 3% obtained by diluting commercially available HCl (20%) in water at a ratio of 15 ml of

commercial hydochloric acid in 1 litre of water, and leave the resulting mixture for 12–18 hours. For

optimal detachment of seeds from the placenta, temperatures of 35–40°C over a period of 12 hours

allows polygalacturonases enzymed naturally present in the pulp and juice to degrade pectines.

Wash the seeds in a strainer under running water and dry them on filter paper or a paper towel at

room temperature for one week, or alternatively in a ventilated oven at approx. 40°C for 24 hours.

Store the seeds in plastic or paper bags or vacuum

packed in a chamber at 4°C and less than 30% of

UR or in a no-frost fridge. Under these conditions,

the seeds can be stored for up to 15 years.

Before sowing, disinfect the seeds by immersing them in a

solution of 70% alcohol (ethanol) in a stirrer for 5 minutes

(the quantity depends on the number of seeds - for fewer

than 50, it is possible to use 10–15 ml ethanol). Then remove

the ethanol by placing the seeds in a strainer under running

water. Then immerse them in a solution obtained by diluting

commercial bleach with water at a ration of 1:2. Finally, place

the seeds into a stirrer once more and wash them under

running water.

To enhance germination, you can use gibberellin by

preparing a solution using a tablet of 5 grams of commercially

available gibberellic acid in 1 litre of water.

B. oleracea plants are usually self-incompatible and need to cross with other genotypes to generate progenies. The self-incompatible genotypes require specific management for controlled

pollination achieved by spatial isolation in the field or by the use of pollination chambers to avoid pollen contamination by pronubes.

The protocol to regenerate landraces or their selections by avoiding pollen contamination is

transplanting plantlets (3rd–4th leaf stage) into 10-litre pots filled with a peat/perlite substrate

(1:1 in volume). Plants are usually grown in the open until they reach the flowering stage and then

moved to pollination chambers either in a cold greenhouse or an open field. In some cases plants are

transplanted directly into the field and we then use isolation chambers.

The pollinators used are flesh flies (Sarcophaga

carnaria) because they are more efficient for small

pollination chambers than bumblebees or honey

bees. Their larvae, about 1000–2000 bought in fishing

shops each week, are developed into flies in one-litre

containers filled with peat and covered by a net until

the adult stage is reached. Metamorphosis occurs

when the temperature is between 13°C and 28°C. On average, 70–80% of

larvae reach the adult stage. Metamorphosis takes

place at 8 and 18 days at 28°C and 13°C, respectively

(this is very important to synchronise the availability

of adult flesh flies with plant flowering).

Adult flesh flies are released into the isolation

chambers when the plants reach the flowering stage.

During the presence of the flies in the pollination

chambers we can use protein-rich commercial

products to prolong the life of the flies, especially when there are few flowering

plants to feed them. At the end of the flowering

stage the plants are moved from the chambers to

the field to complete the fruit ripening stage.

Organic agriculture uses organic seeds or untreated conventional seeds when no alternative exists.

In both ways, seeds can carry diseases and are better treated using a method which

• is acceptable for organic farming

• has a good success rate at disinfecting

• does not significantly reduce the germination rate.

Prior to sowing your beans, this simple method can reduce or even remove seed infections.

For this you will need: a container, hot water (55°C), cold water and a thermometer.

If you have several lots to treat at the same time, you can use a cheese cloth or a mousseline cloth.

Make sure that you have at least 4 volumes of water for 1 volume of seeds.

You can also put the seeds in individual glass bottles filled with water at the right temperature and kept in the water bath.

Ensure the water is at 50°C for the whole 10 minutes duration of the treatment.

Re-drying takes a total of 6 hours at 25°C with an air dryer (1 hour running and a ½ hour break) or can be done overnight using a regular home ventilator.

Always treat your seeds close to the date of sowing as the wetting might speed up germination and check your plants for disease symptoms: while this method is usually successful at removing pathogens, it can like all methods sometimes fail.

Part of a bean variety trial of BRESOV, this method was used on all lots including a lot infected with Xanthomonas. The seeds were successfully cultivated, beans were harvested and no symptoms of Xanthomonas were observed. Many seedborne diseases are systemic and may be unnoticeable during cultivation but manifest later in the seeds.

Therefore, if you use this method to produce seeds, you should send a sample to a seed-testing laboratory to confirm they are pathogen free.