Pioneering marker-assisted breeding results in pearl millet hybrid resistant to downy mildew

Farmers growing pearl millet in Haryana and Rajasthan need not fear the downy mildew (DM) disease any longer. Collaborative research between the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) and the Haryana Agricultural University (HAU) has resulted in the development of a new hybrid, HHB 67-2, which is resistant to downy mildew. It is the first ever product of marker-assisted breeding in pearl millet to be released for cultivation in India.

With the Haryana State Varietal Release Committee approving the release of HHB 67-2 on 14 January, there are possibilities of the new hybrid’s seeds reaching the farmers this coming rainy season. The new hybrid HHB 67-2 is an improved version of the popular pearl millet hybrid HHB 67, which again was a result of collaborative research between ICRISAT and HAU.

According to Dr William Dar, Director General of ICRISAT, this significant breakthrough is a result of ICRISAT’s cutting edge scientific research and effective partnerships. The new hybrid HHB 67-2 brings to the farmers additional benefits, even while retaining the qualities of the earlier popular hybrid.

Dr C Tom Hash, ICRISAT Principal Scientist, said that the release of the new hybrid HHB 67-2 represents the delivery to the farmers the first product of a 15-year series of projects supported by the Department for International Development (DFID) of the UK Government. The continuity of this support was critical to the research team being able to deliver the new hybrid.

The original HHB 67 is now grown on at least 400,000 hectares in Haryana and Rajasthan. It was released in 1990 by HAU and is very popular since it matures very quickly – within 65 days – thereby escaping the end-of-season drought and providing an opportunity for double cropping. Unfortunately, there has been no alternative available in its maturity group. In the recent years, HHB 67 was starting to succumb to DM. Since HHB 67 is highly preferred by the farmers for more than a decade, attempts were made to improve the parental lines of HHB 67 for DM resistance. This was successful and after testing the resulting hybrids for three years, the best of these has been identified for release as HHB 67-2.

The fungus Sclerospora graminicola causes DM, a major disease affecting pearl millet. If the plants are infected at an early stage, their growth gets stunted and they die. Infection at later stages results in failure of grain formation.

By rapidly adopting the improved hybrid HHB 67-2, farmers in Haryana and Rajasthan can avoid grain losses approximating Rs 28.8 crores, in the first year of a major DM outbreak. In years of severe DM attack, up to 30% of the pearl millet harvest can be lost. The income losses due a severe DM outbreak on HHB 67 can be estimated from an average grain yield of 800 kg per ha, and a minimum selling price of Rs 3 per kg.

To develop the new hybrid HHB 67-2, the parental lines of the original hybrid were improved for downy mildew resistance through marker-assisted as well as conventional backcross breeding programs at the ICRISAT campus at Patancheru.

The gene for downy mildew resistance was added to the male parent, H 77/833-2, through marker-assisted breeding using ICRISAT elite parent ICMP 451 as the resistance gene donor. A PhD student from HAU working with ICRISAT’s team carried out this marker-assisted backcross breeding work. The gene for DM resistance was added to the female parent, 843A/B, from ICRISAT line ICML 22 through conventional backcross breeding. The All India Coordinated Pearl Millet Improvement Project (AICPMIP) did the field-testing of the new hybrid at various locations over the past three rainy seasons.

By using biotech-based molecular marker-assisted selection, the male parent for HHB 67-2 could be developed in one-third of the time required for the developing the female parent by conventional selection methods. By identifying and marking the gene responsible for DM resistance in ICMP 451, it could be checked whether the gene had transferred to the next generation in the progeny of crosses between ICMP 451 and the male parent of HHB 67. By using molecular marker technology the presence of the gene can be tested even while the next generation is a seedling, saving precious breeding time. In conventional breeding, the presence of a gene can be verified only after the plant grows to maturity and seed from an individual plant is sown to screen for the DM resistant character.

ICRISAT has produced Breeder Seed of the parental lines of HHB 67-2, which can now be used to multiply the hybrid, and this will be supplied to seed multiplication agencies.

Source: Crop Biotech Update

With the help of marker assisted breeding (MAB), the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) and the Haryana Agricultural University (HAU) have developed a new pearl millet hybrid resistant to downy mildew (DM). The hybrid, designated HHB 67-2, is the first ever product of marker-assisted breeding in pearl millet to be released for cultivation in India.

DM is caused by invasion of the fungus Sclerospora graminicola. Infection of millet at early stages of development can result in stunted growth of the plant, or even death. Infection at later stages results in failure of grain formation. In years of severe DM attack, up to 30% of the pearl millet harvest can be lost.

To develop the new hybrid HHB 67-2, parental lines of the original hybrid were improved for downy mildew resistance through marker-assisted as well as conventional backcross breeding programs. The gene for downy mildew resistance was added to the male parent, H 77/833-2, through marker-assisted breeding using ICRISAT elite parent ICMP 451 as the resistance gene donor; while the gene for DM resistance was added to the female parent, 843A/B, from ICRISAT line ICML 22, through conventional backcross breeding.

For further information, contact Dr CT Hash at c.hash@cgiar.org