Surveys and inventories of plant genetic resources

Understanding crop diversity, including its distribution and changes over time, is a crucial prerequisite for the development and implementation of effective and efficient conservation strategies. Various studies have been conducted to survey and inventory plant diversity across different regions in Yemen by agencies such as the Agricultural Research and Extension Authority (AREA), colleges of agriculture and sciences in Yemeni universities, and institutions like the Social Fund for Development (SFD).

Al-Khulaidi (2013) reported the identification of 2,838 plant species, as part of the Yemeni flora, of which 2,602 are native, 129 are cultivated and 107 are introduced. Among these species, 608 were found to be endemic or semi-endemic (457 are endemic, among which 307 on Socotra Island alone), confined to Yemen or the Arabian Peninsula. The diverse topography of Yemen's plains, mountains, plateaus, valleys and deserts, with varying altitudes, has contributed to the emergence of this unique plant diversity in the country.

The uniqueness of such diversity extends to the varied crops grown in the country, which includes both tropical and temperate crops. Additionally, there is a diversity within species, with multiple crop varieties adapted to different environments or agroecological zones in the country. For instance, sorghum is characterized by a great diversity of types that mature over a range of durations (after three, four, five or even six months).

Table 1 presents the results of some recent studies and surveys, which involved counting and classifying plant species, compiling lists with their scientific and local names, providing photographs, and mapping their distribution in specific areas. These studies also identified the uses of the plant species, such as food, fodder, medicine and other purposes. Additionally, they focused on identifying threatened, rare, endemic and semi-endemic plants, some of which are introduced plants.

On-farm management and improvement of plant genetic resources for food and agriculture

Plant diversity plays a vital role in food security and adaptation to climate change. Therefore, it is crucial to focus on on-farm management and improvement of local crop varieties, including neglected and underutilized crops. By doing so, the resilience and adaptability of the cropping systems can be enhanced, enabling better withstanding of biotic and abiotic stresses and eventually better production and food security for the farmers’ households.

NGRC has undertaken various activities to support the management and improvement of genetic resources on farm through multiple projects (Table 2). These initiatives primarily involved the characterization, evaluation and dissemination of local varieties suitable for different agroclimatic zones. The germplasm collected by various projects has been safety duplicated at the national genebank. The aim was to increase genetic diversity and broaden the range of options available to farmers for selecting varieties that are well-adapted and tolerant to biotic and abiotic stresses prevalent in their specific local conditions.

Providing seeds to farmers and researchers in case of disasters to restore cropping systems

NGRC is ideally positioned to play an important role in preserving plant genetic resources, especially in the face of natural disasters (such as droughts and floods) and man-made disasters (like conflicts and wars). NGRC's mandate includes providing high-quality seeds adapted to farmers' environmental conditions in disaster-affected areas, in coordination with relevant National authorities and organizations like regional agricultural research stations, the General Improved Seed Multiplication Corporation (GISMC), the Public Corporation for Grain Development and Production (PCGDP), and provincial MAI offices. However, due to limited material and human resources, NGRC's efforts are constrained, particularly in the current challenging conditions within the country.

In 2016, the regional station for agricultural research in the western coastal plain (Al-Kadan, Sardoud, Tihama region) was severely damaged by airstrikes. The seed stores in the station were significantly affected, leading to spoilage and loss of different varieties that had been collected and preserved by the station's researchers over many years (Figure 1).

Nonetheless, NGRC has managed to provide services to farmers and researchers in conflict and war-prone zones in some instances. This has been achieved through quality testing of locally distributed seeds and by providing seeds of important local strains to research stations in the respective agricultural regions.

For example, NGRC collaborated with other organizations and international agencies operating in Yemen to provide seeds of cereal, legumes and vegetable crops to affected farmers as part of humanitarian relief activities. Organizations such as FAO, the Red Cross, Acted and others have contributed to seed distribution efforts. However, the distribution mechanism faced drawbacks, including poor coordination with official agencies, poor seed quality and sometimes unsuitable seeds for the targeted agricultural climatic zones. These issues created a negative impression among farmers and decision-makers regarding the effectiveness and safety of the distribution mechanism.

In response, measures were established to mitigate these negative effects. These measures included conducting seed quality tests in laboratories, seed screening and purification by GISMC, and ensuring direct coordination with government authorities and institutions in the targeted areas.

Unfortunately, there have been instances where poor-quality seeds have been distributed. In April 2021, MAI destroyed a large quantity of rotten seeds that were provided by FAO for distribution to farmers in Al-Hodeidah governorate. The spoiled quantity was estimated to be more than 240 tonnes. These seeds, intended as donated assistance to Yemeni farmers, were infected with fungi and deemed unsuitable for cultivation.

This incident highlights the importance of strict quality control measures and coordination among relevant authorities and organizations to ensure the effective and safe distribution of seeds in Yemen in line with the recommendation of the International Plant Protection Convention (IPPC) on “ensuring safe provision of seed during humanitarian assistance disbursement” (IPPC, 2021).

Changes and trends in on-farm genetic resources conservation

Yemen is known as one of the main countries that are growing qat. Qat or khat or khata (Catha edulis) is a mild stimulant plant consumed by most Yemenis in a daily afternoon session by chewing its fresh leaves (Zahran, Khedr, Dahmash, & El-Ameir, 2019). The expansion of qat cultivation at the expense of the main cereals and legumes (sorghum, millet, wheat, barley, lentil and pea) poses a significant threat to crop diversity in Yemen. The yearly agricultural statistics book indicates a decline in the cultivated area of cereal crops over the years, while qat cultivation has increased (GDSID/MAI, 2022). However, the actual increase in qat cultivation may be even greater than what is reflected in the official figures (Figure 2). Due to the war and resulting consequences, including the institutional divide and ineffectiveness, no agricultural census has been conducted for the past two decades.

The urban population expansion on agricultural lands is another factor threatening crop diversity. Figure 3 shows the trend in population growth over the past 70 years.

A study conducted by the Renewable Natural Resources Research Center (RNRRC) in 2021 on the urban expansion in Dhamar governorate revealed a dramatic increase over the past 50 years.

Reports from field surveys conducted by NGRC and RNRRC highlight the expansion of urban centres and population at the expense of agricultural lands (Figure 4). This phenomenon is considered one of the most critical factors endangering agricultural biodiversity.

The disappearance of certain plant species and fruit varieties (quince, walnuts, pear, peach, apricot, fig and grapes) from areas like Sana'a governorate, which used to be known for cultivating them, further emphasizes the negative impact of urban expansion on agricultural biodiversity. Parks and orchards (for example of walnuts, peach and grapes) have been replaced by commercial and residential areas, resulting in a significant decrease in green coverage.

On the other hand, there has been an expansion in the cultivation of some vegetable crops (tomato, onion, potato, pepper, carrot, cucumber, zucchini, cabbage), including varieties introduced from abroad. Although the cultivated area of vegetable crops fluctuates, the number of greenhouses in different regions of Yemen has increased. Strawberry cultivation has also grown in response to high demand from fresh juice shops in major cities.

The cultivation of fruit crops, particularly almonds, has expanded due to relatively low water requirements and the profitability of production. The almond cultivation area has increased between 2011 and 2020, with significant expansion in Sana'a governorate, particularly in the districts of Al-Haima and Bani Matar.

Coffee cultivation has also expanded due to increasing demand for Yemeni coffee locally and internationally. The cultivation area has increased over the past few years much more than the estimated figures made in the agricultural census book for 2020, which indicated an increase of 2,000 hectares in the coffee area between 2016 (33,900ha) and 2020 (35,900ha). Also, there has been a focus on improving agricultural processes and post-harvest operations to meet desired quality standards. High government authorities and MAI have shown increased interest in the coffee sector, establishing the National Center for Coffee Research and supporting farmers' associations. A decree was issued in 2022 banning the import of both processed and unprocessed coffee from abroad to encourage domestic cultivation and increase the income of coffee farmers.

Overall, while there is an expansion in certain crops, the threats to crop diversity posed by the expansion of qat cultivation, urbanization and population activities remain significant challenges in Yemen.

Supporting the targeted collection of plant genetic resources

The primary drivers for implementing targeted collecting of genetic resources were the risk of loss of on-farm diversity, opportunities for use, and the need to address deficiencies in ex situ conservation.Bawazir (2004) conducted a study on cereal diversity in southern Yemen and emphasized the importance of surveying and collecting genetic resources of cereal crops and their wild relatives across different agroclimatic zones in Yemen. The study aimed to document these resources and utilize them in breeding and genetic improvement programmes.

The study's findings revealed that sorghum varieties in these areas exhibited genetic variation within each environmental zone, as evidenced by differences in phenotypic characteristics, anatomical features and resistance to environmental stress conditions. The researcher pointed out that the varieties of sorghum grown in coastal areas showed early maturity (100–120 days), while the varieties grown in the highland areas matured late (160–180 days). According to the study, sorghum varieties in the highland areas were tallest (300cm) while in the coastal areas plant height ranged from 250–300cm.

The study also demonstrated that local wheat varieties possessed drought tolerance. This may be accounted for by their morphological and anatomical traits, such as the smaller number of seminal roots and the small size of seminal root vessels. Most of the local varieties of wheat grown in the southern, medium-altitude regions of Yemen belong to Triticum aestivum. In some areas, there may be a mixture of T. aestivum and T. durum.

The local varieties of millet grown in the southern Yemeni regions belong to Pennisetum glaucum (pearl millet), Pennisetum setaceum, Pennisetum rigidum (little millet) and Eleusine coracana (finger millet). Misibli is the local name for pearl millet throughout Yemen, Kanab is the local name for finger millet, and Heba is the local name for small (short) millet (and an early-maturing type) on Socotra Island.

The efforts made in collecting and conserving plant genetic resources in Yemen can be divided into three phases:

1) First phase (1970s and 1980s): During this period, international organizations collaborated with researchers from the El-Kod Research Station in Abyan governorate and the Southern Highlands Regional Agricultural Research Station (SHRAR) in Osaiferah, Taiz governorate to collect hundreds of samples. Notable collecting missions during this period in the different Yemeni regions are presented in Table 3.

Unfortunately, all the samples collected during this period were lost due to inadequate storage conditions, except for those preserved outside Yemen by supporting organizations, such as FAO, the International Plant Genetic Resources Insitute (IPGRI), the United States Agency for International Development (USAID), the International Maize and Wheat Improvement Center (CIMMYT) and others (Al-Mua’alem, Mansour, Jahlan, & Al-Ghaz, 1993).

2) Second phase (1990s): During this period, a specialized unit for plant genetic resources was established under RNRRC of AREA in Dhamar. Over 2,000 plant samples were collected during this phase. Notably, a joint team from AREA and the International Center for Crop Research in the Semi-Arid and Arid Tropical Areas (ICRISAT) conducted significant collecting trips. They collected 685 seed samples, mostly of sorghum and millets, from Al-Dhalea, Radfan, Yafe’a, Abyan, Lahj and Tehama. Details on this collection trip and other trips are presented in Table 3.

Despite having a refrigeration room for cold storage (-18˚C), frequent power shortages and blackouts led to the loss of many collected samples, despite their data being recorded in NGRC's records.

3) Third phase (2000s to present): This stage witnessed the establishment of NGRC in 2002, an increase in specialized staff and the establishment of various departments within the centre. FAO stated that NGRC in Dhamar held 3,281 samples in its genebank (FAO, 2009). The number of samples collected from different regions of the country has increased to over 6,500 accessions at present. Notable collecting operations, covering most Yemeni governorates, conducted by NGRC during this phase are displayed in Table 3.

The collecting trips conducted by NGRC between 1989 and 2013 to collect seeds from natural and cultivated plants, targeting all geographical regions in Yemen are shown in Figure 5.

Most of the collection activities previously reviewed were carried out with support and funding within bilateral or multilateral cooperation or joint work projects between Yemen and several partners over the previous decades, and copies of samples of genetic resources that were collected found their way abroad and have been preserved by institutions outside Yemen. Early reports indicate that over 8,000 samples were deposited in various genebanks abroad (Al-Ghouri et al., 1996). The Second National Report on the State of Plant Genetic Resources for Food and Agriculture stated that international organizations held 8,619 samples from Yemen (FAO, 2009). Currently, data on the Genesys platform show 8,958 samples from Yemen conserved in 19 genebanks, covering 44 plant species, with a focus on grain crops (Genesys, 2021). Data from FAO WIEWS and the Svalbard platform also align closely with these figures (Table 4).

Expanding diversity in genebanks

It is crucial to expand ex situ conservation efforts for neglected crops, crop wild relatives and forages to facilitate research and crop improvement. The genebank of NGRC currently conserves seeds from 45 different crops. These crops encompass cereals such as sorghum, maize, millet, wheat and barley; legumes including lentils, beans, kidney beans, cowpeas, peas and fenugreek; vegetables like onions, tomatoes, chilli peppers, cucumbers, zucchini, mallow, radishes, eggplant and okra; oil-producing crops like sesame and peanuts; less commonly utilized crops, such as black seed (Nigella sativa), henna (Lawsonia inermis), coriander (Coriandrum sativum), caladium, arugula (Eruca sativa) and mustard (Brassica juncea L.).

Additionally, field genebanks situated in various regions hold a diverse range of crops, including date palms, mangoes, citrus fruits, almonds, grapes, bananas and papayas, along with forage and forest crops. There are eight field genebanks in various regions – the northern, central and southern highlands, the Tihama coastal plains region, the southern coast region (Al-Kud, Abyan) and the Eastern Plateau region (Marib and Sayun). More details are provided in Table 5.

It is important to note that the acquisition of new species and samples to expand the genetic resources reserve at NGRC was temporarily halted between 2014 and 2018 due to the prevailing conditions of the war and the resultant socioeconomic deterioration and institutional ineffectiveness in the country.

Efforts have also been made to conserve genetic resources of threatened and endemic species ex situ in various research stations located in different agricultural regions. Notably, a specialized team from the El-Kod research station in Abyan governorate collected the Socotra wild pomegranate (Punica protopunica Balf. f.) in 1989 and 1990. This threatened species, which is endemic to the Island, has been confirmed by international organizations such as the International Union for Conservation of Nature (IUCN) to be one of the species at risk of overexploitation without natural regeneration. The collected seeds were grown, and the trees were nurtured at the El-Kod research farm (Bazara’a, 2000).

Regeneration and multiplication of genebank seed samples

Even under optimal storage conditions, it is necessary to periodically regenerate and multiply seed accessions due to the decline in viability over time and the limited quantity of preserved seeds resulting from their distribution to users such as researchers and farmers.

Hence, NGRC carries out annual processes to regenerate seed accessions that are at risk of viability loss and to multiply accessions with limited quantities. The most recent regeneration and multiplication initiative was conducted by NGRC in 2014. Due to the prevailing war conditions, regeneration operations were suspended from the beginning of 2015 until 2020, resulting in no activity in this regard during that period. Subsequently, with the initiation of the ‘Participatory Conservation and Sustainable Use of Local Varieties’ project, funded by the Benefit Sharing Fund (BSF) of the ITPGRFA, approximately 200 plant accessions (mainly cereal crops) were regenerated in the governorates of Dhamar and Hadramout (Seiyun) (FAO, 2023).

Table 6 shows the numbers of seed samples that have been regenerated until 2014 and those still requiring regeneration, as reported by NGRC in Dhamar.

Conservation changes and trends in genebanks

The study period witnessed several notable positive changes and trends in the field of genebank conservation, including:

• Increase and expansion of plant samples: The number of seed accessions in the NGRC genebank increased from 3,281 in 2006 to approximately 6,500 accessions in 2021. Similar growth was observed in the Genetic Resources Center (GRC) of Sana'a University, with the number of accessions rising from 1,528 to over 3,000 (Table 5).

• Improved energy security: Noteworthy progress was made in securing electrical energy for cold storage in the NGRC genebank in Dhamar. Solar energy systems were introduced in 2016, funded by the Agricultural and Fisheries Production Encouragement Fund (AFPEF). Additionally, the Public Corporation for Grain Development and Production (PCGDP) provided a solar energy system for the GRC at the Faculty of Agriculture, Sana'a University, in 2019.

• In 2022, with support from the Crop Trust and the ITPGRFA, the NGRC genebank in Dhamar was provided with several solar energy batteries to improve the electricity supply for cooling the long-term seed storage.

• Safety duplication: Copies of seed accessions from cereal and leguminous crops were sent to ICARDA in 2013 and subsequently stored in the Svalbard Seed Vault (Table 4).

However, there were also negative changes and trends observed in germplasm conservation in genebanks.

Negative impact on field genebanks: The conservation of plant genetic resources in field genebanks managed by research stations across the various regions was significantly affected by the war and its associated socioeconomic and institutional consequences. The lack of operational budgets hindered essential agricultural activities such as ploughing, levelling, weeding, pruning, grafting, fertilizing and irrigation. Fuel shortage and high prices further exacerbated the challenges faced by research stations in adequately maintaining the field genebanks. In certain field genebanks in the northern (Al-Errah) and central highlands (Dhamar), some fruit trees were cut down by residents for firewood during periods of gas shortage and high prices resulting from the war and siege (Figure 6). Complete destruction of field genebanks occurred in the Southern Highlands Agricultural Research Station (Osaiferah, Taiz) for mango, guava and coffee varieties, as well as in the Southern Coast Agricultural Research Station in El-Kod, Abyan governorate. Similarly, the field genebank for pomegranate at the College of Agriculture and Veterinary Medicine, University of Dhamar, experienced the same fate, with all preserved trees being cut down due to war and siege conditions.

Limited implementation of biotechnologies: The use of biotechnologies, such as tissue culture, for the conservation of plant genetic resources has not been possible due to a lack of resources, including electrical energy sources, laboratory materials and equipment. Thus, no duplicates of the accessions maintained in field genebanks had been maintained in tissue cultures and thus, as safety duplicates.

Limited multiplication and regeneration of seed samples: Except for a limited number of seed accessions regenerated and multiplied through funded projects such as the ‘Participatory Conservation and Sustainable Use of Landraces’ (2019–2023) (NGRC, 2022) and activities supported by the General Corporation for Grain Production and Development, the war's economic effects halted vital regeneration programmes and seed multiplication activities. Improper storage conditions, insufficient seed quantities and difficulties in providing seeds to farmers and researchers have led to a decline in seed viability. Hundreds of samples are currently at risk of spoilage and loss, requiring regeneration and multiplication.