Продолжение рекомендаций Bayer на тему действий после обнаружения вируса ToBRFV в хозяйстве. Кому-то может пригодиться. На английском, переводить некогда.

Growing with ToBRFV - a new reality: Minimizing the virus spread after detection

Where Tomato Brown Rugose Fruit Virus ( ToBRFV) is detected, growers must find the right balance between continuing with their normal levels of hygiene or taking extra hygiene precautions. This article wants to help find the right balance and determine which measures will be useful – and why – for your location. Slowing down the spread of the virus after it has been detected may potentially lead to the production of a better crop and a higher yield compared to no action taken. "The virus moves with plant material, with water, with people, with equipment and through the air", says Harmen Hummelen; Vegetables By Bayer Field Quality Lead, explaining further on how to act.

Basics

There are 3 basic steps:

1. Make sure that plant growth is good by adjusting the climate and reducing crop stress.
2. Ensure basic hygiene is in place. For example, this means – without exhaustive hand washing, cleaning equipment, and reducing direct contact with infected plants by people and equipment.
3. Stop the virus moving through the greenhouse. ToBRFV is mechanically transmitted, so it can 'hitchhike' to the next plant on all kinds of materials and equipment. These transport routes have to be blocked as much as possible.

This article will focus on point #3.

People and virus transmission
People pose a high risk of spreading the virus. Not every person poses the same risk or even considers him- or herself as being a risk. Creating awareness about how virus transmission happens is the first step towards managing the spread.

Workers are the largest group who interact with the crop every day. There may be full-time employees and temporary workers. It may be that some workers can work in different tomato greenhouses yet use the same car or live in the same house. Their personal belongings may be mixing, for example shoes next to each other or even exchanging shoes. This is an example of how the virus can be moved from greenhouse to greenhouse through clothes or shoes off-site. Some workers may also work at multiple locations, sometimes on the same day.

Workers may grow tomatoes at home or bring store-bought tomatoes for lunch. These risks need to be mentioned to the workers and, if possible, reduced.

Owners and managers are also a high risk because they may bypass hygiene protocols to complete actions quickly. But any interaction with plants, equipment, or structures can lead to the virus being picked up and moved. A quick visit by a manager or owner is enough to help the virus move to another plant. It is often very difficult for managers, owners, and the parents of owners to adapt to a new way of working and not to be able to 'quickly' visit a greenhouse.

External visitors are always seen as a high risk, particularly if those people visit other tomato or horticultural locations. Some of these visitors are fully aware of the risk and take good precautions. Other visitors, like contractors repairing or building, are often not plant- or 'green'-minded and do not see any risks. Both groups should follow strict protocols before entering the location. This includes not allowing equipment from other locations to enter the greenhouse without cleaning.

Visualize transport routes of the virus
The virus moves with plant material, water, people, equipment, and through the air. The virus is not visible, so workers can find it difficult to visualize or imagine. A helpful tool can be to draw a picture of the greenhouse with all the routes that plants, people, water, and equipment follow, and which doors are used.

All these steps can be listed, and a risk assessment can be carried out. Many of these steps are in the mind of you as a grower or technician, but it is also very useful to get other people, including workers and managers, to add to the list. This helps everyone to know all the risks and reduces the risks of some steps in the process being forgotten.

Reviewing the list 1 or 2 times a year helps keep people alert to the risks and keeps the assessment up to date. Reviewing can be done by management, but asking workers to join is really helpful in hearing what is really done in the greenhouse. Workers helping with the risk assessment will also feel more involved and will take better care and can be ambassadors in the greenhouse for better hygiene.

An example of a drawing of the greenhouse is shown in the below picture. Lines are drawn to show walking routes, and doors and disinfection locks are also shown. If this overview of the greenhouse is printed on a big piece of paper and put in an area such as the canteen people are more likely to discuss it. Discussion creates awareness and people will be more involved and supportive.

Figure: Example of schematic drawing of a greenhouse showing all the people and equipment moving lines. Making such an overview helps identify all possible routes of entry and spread of a virus in the greenhouse.

Example, Risk assessment table
Examples are given of risks, along with example scores for the likelihood, impact, and risk level (1 being lowest, 5 being highest). Every company should make their own list of risks and determine their likelihood, impact, and risk level. Overall risk is determined by multiplying the likelihood with the impact.

If risks are known, actions can be defined and executed.

Extra measures after virus infection
Hand washing and changing shoes and clothes is becoming a basic hygiene measure at many locations. This creates a cost, and it can be discussed if this has to be done the whole year (however, it should be considered whether the potential cost of lost crops due to ToBRFV is likely to be higher than the costs of good hygiene). Stricter rules for the first 3-5 months after an initial infection is found can be a good compromise. After some months, the virus may be so widely spread that prevention levels might be lowered, depending on the balance between cost and risk a company wants to take.

Separating the first infection spots is certainly useful at the beginning. One hypothesis is that the virus moves 2-4 rows away from the initial infection (hotspot) every week if no hygiene measures are taken. Extra hygiene in those rows and working in this area by dedicated people and, at the end of the day, slows down the spread.

The experience is also that a first hotspot is often followed by other spots some weeks later. Because the virus has probably moved from the first hotspot to other locations before it was visible. Separating the first hotspot can also reduce the number of secondary spots.

In case of a late infection (e.g., 6 months after planting and in summer), we have seen that removing the hotspot by removing plants in the adhering 3-6 rows can 'stop' the infection from spreading. This removal of plants feels very rigorous, but the spread is stopped because there are no plants anymore, and workers are not going into those rows and are not contaminated. This also reduces the risk of secondary spreading. In older crops, the balance between destroying or extra hygiene can be in favor of destroying some rows.

Separated blocks
A good basic measure is to divide a greenhouse into blocks with separate people and equipment for each block. Reducing the number of crossing lines between blocks also reduces the spread of the virus all over the site. The size of these blocks depends on your company and can be based on the way the greenhouse is built for example, if the greenhouse is square, 4 blocks may be ideal. In many cases, the people and harvested fruits are still moving over the same main path or corridor, which is not optimal but does reduce the exchange of viruses.

If possible, trolleys and harvesting crates should also be dedicated to a certain block. This way of working is not easy, and the optimal size of a block seems to be between 1 and 5 hectares. The idea of blocks can be useful not only for virus control, but also to treat only affected parts of the site with other pests or diseases.

A ToBRFV infection can easily happen, and taking precautions and being prepared is the first step to take measures that are working and reasonable. A risk assessment and making people aware support this approach. In general, the later an infection starts and the less the virus is spread, the better it is for the plants and for the final yield.

For more information:
Bayer
www.bayer.com

Publication date: Wed 17 Apr 2024

Research shows uneven virus increase and distribution in plants

Tomato Brown Rugose Fruit Virus (ToBRFV) is not 'infecting' the plant and plants in a row in an equal way. The virus wants to be where the active growing points are and multiplicate there fastest. Viruses prefer some parts of the plant more than other parts. This is the conclusion of an experiment conducted by Bayer in red coloring truss tomatoes.

Virus increase in plants
There seems to be a big difference in ToBRFV increase between tomato plants. In the case of the experiment, we looked at an uncontrolled natural infection at a grower's location. Individual plants on the same gutter were tested every 2 weeks, sepals of the red fruits, see graph, with the RT-qPCR method. The lowest amount of virus that can be detected reliably is around a Ct 32. For that reason, the graph starts at 32. In case of an active infection the Ct value goes down in time, meaning the virus amount increases.

The graph shows that in 2 weeks' time the virus increases strongly, with several plants going from Ct 30 till around Ct 15 (rows e and f). Other plants are still around a Ct of 30. The plants in row e and f continue to show decreasing Ct values reaching a Ct around 10 after 4 to 6 weeks.

Looking at row b (the red line) this plant is maybe not really infected at 0, 2 and 4 weeks, as the Ct is around 30. The low levels of virus being detected may be virus coming from neighboring plants, meaning that the virus is lying on the outside of this plant rather than internal infection. Six weeks after starting testing, the Ct is 21 indicating virus infection is present, and in the weeks after the Ct values continue to drop.

The group of plants with an early infection shows a strong initial drop in rows e and f (lines in blue and green). Plants in these rows which are tested later in time seem to have a slower increase of the virus.

First measurement was towards the end of April and 4 weeks later it is half May, and in those plants the virus increase seems reduced.

After 4 till 10 weeks all plants are becoming heavily infected reaching a Ct value around 10.

ToBRFV increase in tomato plants over time. ToBRFV virus presence was measured with RT-qPCR and expressed in Ct values. Lower Ct values means higher virus numbers.

2 stems other infection level
Monitoring for ToBRFV in 2 stems of 1 plant in which the stems are hanging in 2 different paths, showed in some cases a big difference of virus concentration. The difference in virus concentration was up to 15 Ct points in the following weeks and differences in visible symptoms were also observed.

This was surprising because it was expected that virus would be spread from the stem through the stem base and roots then to the other stem of the plant. It looks like the 2 heads of the plant may be more or less autonomous. It is known that the above plant parts are in contact with their 'own' roots but virus exchange was expected to occur as it is a shared rooting system. This is only a small experiment and this may not be standard in all cases.

Tomato plants were tested with RT-qPCR for ToBRFV concentration. Lower Ct values mean higher virus numbers. Plant stems were hanging in 2 different paths, indicated as left and right from 1 plant. Week 0 is the beginning of June; biweekly testing is done till the half of July.

Observations
Plants on the same slab or gutter can have different viral loads. The viral load is even different between the 2 stems on the same rootstock of 1 plant hanging in different paths. Both observations indicate that the roots are probably not the most important transmission way for the virus.

It looks like the transmission of the infection between the top of the plants is spreading much faster in the same row. This supports the advice that disinfection of trolleys and gloves is a way to reduce the spreading of the virus.

This article was prepared by Harmen Hummelen, field quality lead, and is #3 of our Bayer's Growing with ToBRFV: A new reality series. Stay tuned for part 4 of this series on ToBRFV on virus prevention after detection, which will be published shortly

For more information:
Bayer
www.bayer.com

 

Publication date: Fri 17 May 2024

https://www.hortidaily.com/article/9627456/research-shows-uneven-virus-increase-and-distribution-in-plants/

Инактивация ToBRFV: определяем эффективные стратегии

Вирус коричневой морщинистости плодов томата считается одной из самых больших угроз для производства томатов из-за своего глобального распространения, лёгкой механической передачи внутри теплиц и пагубного воздействия на товарный вид плодов. Он включён в Единый перечень карантинных объектов ЕАЭС.

Обзорную статью В. Рябининой (ООО «Фитодиагностика») можно прочитать полностью, скачав по прямой ссылке электронную версию журнала Perfect Agriculture за 2-й квартал 2024 года (http://perfectagro.ru/wp-content/uploads/2024/05/ЗГ_спецвыпуск-2-2024_сайт-1.pdf).

Изменено 26 июня пользователем BKB
Поправка.

Прогресс никогда не стоит на месте!

Также в этом выпуске журнала можно ознакомиться с весьма интересным интервью со специалистом компании BASF|Nunhems по селекции томатов для высокотехнологичных теплиц! Кейс Аммерлаан рассказал об значительных успехах фирменной селекции в борьбе с ToBRFV.

Интервью с К. Аммерлааном на русском языке представлено О. Мещеряковой (ООО «ГроуТэк»).

Изменено 26 июня пользователем BKB

В настоящее время все голландские селекционные фирмы предлагают в той или иной степени устойчивые к ToBRFV гибриды. В настоящее время проблема в том, что для этой инфекции нет дефиниции, что означает резистентный (HR), а что толерантный (IR). Над этим работают.

Сейчас многие компании мира предлагаю устойчивые гибриды к ToBRFV, но по прежнему у производителей нет понимания о урожайности новых гибридах, как они себя ведут на светокультуре.

Все производители подобрали гибриды, которые дают в их условиях  лучший экономический эффект, а теперь нужно все менять, подбирать, подстраивать к новым гибридам, на это в лучшем случае уйдет пару лет. Значит в переди долгий увлекательный путь во всем своем великолепии.

Неделю назад ездили в Турцию, посмотрели их гибриды, и как идет работа над устойчивостью к ToBRFV - турки впечатлили, жалко в лаборатории снимать видео и фото было запрещено.  

 

Размышления на тему TOBRFV

Рассказывает Тоби Райт, главный агроном комбината Tom d’Aqui

Итак, если вирус придет ко мне в теплицу и мне придется с ним как-то жить до тех пор, пока не наступит следующий оборот и я не переключусь на резистентные гибриды, что я буду делать?

Я однозначно пересмотрю стратегию выращивания, переведя ее на вегетативный режим. Нужно помочь растению нарастить силы, пока вирус совсем его не поборол и хоть как-то закончить текущий цикл. Хотя с светокультурой будет тяжело реализовать этот план, так как на досветке растения обычно генеративны.
У меня был подобный случай с бактериозом (Clavibacter).

Обычно это заболевание проявляется перед первыми сборами, и ты понимаешь, что деньги утекают от тебя. В этот момент нужно честно ответить на вопрос – смогу я с этим жить дальше? Если мои растения вегетативны – да, я смогу. Если мои растения генеративны – нет, не смогу.

Я сравниваю вирус TOBRFV с тем, как начинался вирус Pepino. Когда появился вирус Пепино в начале  2000-х, все агрономы считали, что наступает конец света. Мы больше не сможем выращивать томат!

Потом мы изучили вирус и нашли способы выращивать и с ним. То же самое и с вирусом TOBRFV – оценка факторов – сможем выдержать или нет.

Все чаще я слышу от агрономов, что есть уже техники выживания в ситуации, когда вирус пришёл на комбинат – они отпускают дополнительные головы, оставляют дополнительные кисти, делают все, чтобы сохранить прогнозируемую урожайность. С такой стратегией вы потеряете процентов 30, но не делая ничего, потеряете все. Это ваш выбор.

С вирусом TOBRFV все зависит от степени поражения. Чем сильнее поражение, тем больше вирус визуализируется на растении. Можно постоянно все дезинфицировать, но толку не будет. Здесь нужна аналитика.

В Нидерландах самые тяжелые случаи поражения были зарегистрированы в феврале. К этому времени растения уже прошли 8 месяцев роста. Растения становились более и более генеративными, слабыми. Это и есть основа понимания заболевания.

Агрономы обычно делятся на две группы:
🍅первые говорят – мне нужна защита, я выбираю резистентный гибрид;
🍅вторые говорят – я знаю свой гибрид, я с самого начала начну делать упор на наращивание силы, подберу вегетативную стратегию, я смогу пройти оборот.

Но что еще нужно учесть? Те, кто выращивают на досветке, выбирают резистентные гибриды, так как их культура гораздо дороже и, если они не смогут вовремя сбалансировать растения, вирус ждать не будет. Покупка резистентных гибридов – это как покупка страховки. Вирус на светокультуре идет очень быстро, вы не сможете выиграть в этой войне.

Источник: www.growtech.pro

Изменено Среда в 17:23 пользователем BKB