CTCRI - CENTRAL TUBER CROPS RESEARCH INSTITUTE

ICAR-CTCRI is the National Active Germplasm Site (NAGS) for tropical tuber crops conserving 5542 accessions comprising important tuber crops like cassava, sweet potato, yams, edible aroids and minor tuber crops. These include around 50 species.

The Field Gene bank (FGB) includes landraces collected from different states of India as well as exotic accessions from Africa, Latin America, China, the Pacific Islands, etc.

Pre-breeding lines (inbreds, inter-specific backcross) of tuber crops and crop wild relatives (CWR) are conserved in the FGB/ net houses.

The Division of Crop Improvement has released 71 high-yielding improved varieties of tropical tuber crops, comprising 20 cassava, 21 sweet potato, 16 yams (9 D. alata, 5 D. rotundata, and 2 D. esculenta), 10 taro, 2 elephant foot yam and 1 Chinese potato. The varieties were developed to cater to the following categories –industrial, food and fodder.

Crop wise database of varieties released by ICAR CTCRI

The developed varieties cater to the following categories: industrial, food, and fodder. They were developed with high yield, high starch, and high dry matter, bio-fortified with vitamins, minerals, and antioxidants, enhanced resistance to biotic and abiotic stresses, climate resilience, nutrient use efficiency, eco-regional suitability, and adaptability to different cropping systems. These include:

• World’s first greater yam hybrid- Sree Shilpa
• World’s first dwarf white yam- Sree Dhanya

The other major highlights are:

• India’s first cassava mosaic disease-resistant variety- Sree Padmanabha
• First hybrid elephant foot yam developed for Kerala- Sree Athira
• First hybrid taro developed for Kerala- Sree Kiran

Cassava Mosaic Disease (CMD) is a major setback for the otherwise prospective cassava industry. To address this issue, many cassavamosaic-resistant varieties were also developed by the Division, which has been a boon to the farming community as well as the Industries.

Climate resilience is an important trait to target under unpredictable and changing climatic conditions. The Division has successfully developed many climate-resilient varieties of cassava (5), sweet potato (10), greater yam (2), white yam (3), and taro (5).

Biofortification is of utmost interest as it naturally fortifies important vitamins, minerals, etc. Biofortified crops fetch a better price in the market and ensure the nutritional security of the nation. The Division developed many naturally biofortified tuber crop varieties, including cassava (3), sweet potato (6), and greater yam (1).

Naturally biofortified cassava and greater yam varieties

Apart from these varieties, few other lines are in the pipeline, which will be proposed to be released soon.

• First varieties in arrowroot, one for the State of Kerala and two for Central release
• First varieties in tannia, one for the State of Kerala and another for Central release
• A non-trailing high yielding white yam variety for the state of Kerala.
• A variety of yam bean, the first from ICAR-CTCRI.
• Two bio-fortified sweet potato varieties

Various biotechnological tools were adopted for the conservation and improvement of tuber crops, viz.,

1. In vitro Active Germplasm (IVAG) for conservation
2. Standardization of in vitro protocols.
3. Standardization of cryopreservation protocols.
4. DNA fingerprinting of released varieties using different markers
5. Standardization of bioprospecting in different germplasm of tuber crops
6. Oomics approaches for the development of improved varieties.
7. Transgenic approaches for quality improvement in cassava.
8. Genetic modification through gene editing
9. Transcriptome sequencing
10. Bioinformatics for gene mining

The major achievements through biotechnological means

1. In vitro conservation was used to maintain and conserve the important accessions and varieties in the in vitro active germplasm (IVAG) at the HQ and the Regional Station.
2. In vitro protocols were standardized for all the major tuber crops, such as cassava, sweet potato, yams, aroids, and minor tuber crops, for conservation under IVAG.
3. Protocols were also standardized for cryopreservation in cassava, yams, and taro using pollen. The viability of cryopreserved pollen from cassava and yams was validated. The cryopreserved pollen was successfully used for hybridization in cassava and taro.
4. Bioprospecting studies were performed on different germplasm of tuber crops to identify novel traits with industrial/pharmacological values.
5. DNA fingerprinting of tuber crop varieties using SSR markers was done.
6. Standardised synthetic seed production for cassava.
7. Standardized transformation and regeneration protocols Indian cassava varieties.
8. Genetic modification through gene editing approaches are also been attempted especially for the development of waxy cassava.
9. Transcriptome sequencing of cassava for drought and PPD as well as TLB in taro was done.
10. Whole genome re-sequencing of cassava elite breeding lines 8S-501 and 9S-127 was successfully completed.

Analysis of 8S-501 and 9S-127 draft genome sequences revealed the presence of 7,789,154 and 7,130,986 SNPs in 8S-501 and 9S-127 respectively. Comparative analysis showed the presence of 1,104,776 and 943,104 InDels in 9S-127 and 8S-501 respectively

The SNPs and InDels identified in this study will be utilized for the identification and development of molecular markers linked to important agronomic traits including high starch, profuse flowering and CMD resistance. The high-quality draft assembly would be helpful for mining SSRs and the development of molecular markers for marker-assisted backcross breeding in cassava.