Oct

Preserving the genetic diversity of dryland crops for posterity: The role of phytosanitation

Elaborating the significance of phytosanitation. Photo: S Punna, ICRISAT

The ICRISAT genebank in India chronicles over 10,000 years of cultivated dryland crops history. It conserves over 120,494 accessions of dryland cereals and legumes from 137 countries. This genetic diversity has also been saved for posterity in the Svalbard Global Seed Vault also known as the ‘doomsday vault’, in Norway. Safeguarding, maintaining and expanding valuable collections in genebanks is a humongous task.

The aim of phytosanitation is to ensure that seed and plant materials are pest and disease free. At ICRISAT, this task is under the responsibility of the Plant Quarantine Unit (PQU). This unit is also responsible for the international exchange of germplasm and for ensuring that the plant material periodically regenerated by the genebank is clean. It services the genebank, the breeding units of the mandate crops and also other CGIAR centers housed at ICRISAT.

As the Germplasm Health Units (GHU) of CGIAR Research Centers observe International Phytosanitary Awareness Week, exceptional achievements in this domain deserve mention. From 1973 to 2016, ICRISAT, in collaboration with the Indian authorities, facilitated export of 1.32 million seed samples of ICRISAT’s six mandate crops and small millets to 173 countries, and imported 180,000 seed samples from 96 countries, without introduction of any exotic pests into the importing country and in India.

International exchange of germplasm is critical to genetic improvement of crop cultivars to meet the ever-increasing demand of food, feed and fodder and also to create backups in other locations in case of a manmade or natural disaster (the recent case of the seed bank in war-torn Syria was an eye-opener for international genebanks for creating emergency backups).

International movement of seed material increases phytosanitary risks such as introduction of exotic insect pests and pathogens. In India, ICRISAT’s PQU, in collaboration with the National Bureau of Plant Genetic Resources (NBPGR) of the Indian Council of Agricultural Research (ICAR) and the Directorate of Plant Protection Quarantine Storage (DPPQS), plays an important role in minimizing such risks.

Photo: ICRISAT

“The role of PQU is crucial to prevent the entry of exotic pests which have the capacity to blow up into large-scale epidemics that can wipe out entire crops,” says Dr Rajan Sharma, Head, Plant Quarantine Unit, ICRISAT. A recent article in the The Guardian on the fall armyworm destroying cereals in Africa clearly illustrates this. “Originally from the Americas, caterpillars eat maize, a staple in many African countries. So far, they have been found in 28 African nations – 16 more than they were detected in five months ago. If nothing is done, they could eat between 20% and 50% of the maize produced in 12 of Africa’s maize-producing countries…” says the article.

Referring to the many stringent measures that are taken at ICRISAT with regard to phytosanitation, Dr Sharma cites the example of how a possible epidemic of downy mildew in hybrid pearl millet was contained.

Major diseases detected

Till date, 69 insect pests and pathogens of quarantine importance have been detected in imported seed materials and 53 in the seed samples processed for exports. The major diseases detected at the post-entry quarantine isolation area (PEQIA) at ICRISAT are:

Fungal diseases

Wilt (Fusarium udum) in pigeonpea from Indonesia (1999)

Blast (Pyricularia grisea) in small millets from Zimbabwe (2003) and Nepal (2012).

Bacterial diseases

Bacterial leaf streak (Xanthomonas vasicola pv. holcicola) and Bacterial leaf stripe (Pseudomonas andropogonis) in sorghum from the Yemen Arab Republic (2003)

Bacterial wilt (Ralstonia solanacearum) in wild Arachis from Brazil (1998), Australia (2000), Malawi (2003) and Senegal (2012).

Viral disease

Peanut stripe virus in Arachis spp. from China (1996), Japan (2006) and Senegal (2012).

Some of these infected consignments could be partly salvaged, while some had to be incinerated.

Screening processes

Photo: ICRISAT

The ICRISAT PQU uses state-of-the-art screening tools and techniques for pest and disease detection that include tests like ELISA, agar and radiography depending on the crop. Suitable seed dressing chemicals are used to eliminate seed-borne organisms during export/import.

The various legal requirements for the issuance of a phytosanitary certificate and import permit are meticulously followed. India is a signatory to the World Trade Organization’s Sanitary and Phytosanitary Agreement and since 1986, NBPGR is the regulating agency for exports and imports. All imported crop germplasm are grown in isolated plots (PEQIA) or the PQ greenhouse for pest and pathogen inspection and release by NBPGR.

Currently, ICRISAT’s PQU is working towards using more sensitive diagnostic tools that facilitate molecular detection of pests and pathogens.

The Germplasm Health Unit (GHU) component is part of the CGIAR Genebank Platform coordinated by the Crop Trust. For more information visit https://www.genebanks.org/the-platform/germplasm-health/

Phytosanitary Awareness Week: For seed and plant health biosecurity

Photo: S Punna, ICRISAT

As part of the International Phytosanitary Awareness Week program, national and regional station heads of ICAR-NBPGR were invited to address ICRISAT scientists on 26 October.

Dr SC Dubey, Principal Scientist and Head, Division of Plant Quarantine, spoke on Importance of ‘germplasm health’ in preventing transboundary spread of pests and pathogens. He cautioned that seed-borne pests and pathogens can survive in genebanks for decades and care needs to be taken to ensure seed health. He said that in India there was a need to improve screening procedures as there have been recent instances where new pests, pathogens and weeds have been introduced through imports. He commended ICRISAT and other CGIAR centers for maintaining a good track record over the last 50 years.

Dr Sarath Babu, Principal Scientist and Officer-in-charge, Regional Station, Hyderabad, spoke on Emerging challenges to international distribution of germplasm. He dwelt on the recent stringent export regulations introduced in India to safeguard the nation’s biodiversity. In fact, a recent article that appeared in the Financial Express tells how Indian officials were able to contain damage on discovering the entry of wheat blast disease from Bangladesh.

In the question-answer session that followed, ICRISAT scientists talked about the difficulty they were facing in exporting material of ‘unknown’ origin or those that had even one line of Indian origin (not FAO designated ) in their pedigree. The officials said that a permission from the National Biodiversity Authority was needed and that with the introduction of online filing, the process is taking much lesser time than before.

Dr Suhas Wani, Research Program Director-Asia, presided over the seminar and urged the scientists to share their learnings from the seminar with colleagues. Dr Rajan Sharma, who organized the seminar, highlighted the role of ICRISAT PQU/GHU in international distribution of pest-free germplasm.