Punjab Agricultural University develops leaf curl virus-resistant breeding lines for cotton crop

By Divya Goyal 

In a breakthrough for the cotton crop cultivation in the region, the Punjab Agricultural University (PAU), Ludhiana, has successfully developed virus-resistant breeding lines against the Cotton Leaf Curl Disease (CLCuD) by utilising a wild cotton species Gossypium armourianum.

Speaking to The Indian Express, Dr Satbir Singh Gosal, Vice-Chancellor, PAU, said that the breakthrough has been achieved after more than two decades of research by the university’s cotton scientists.

″Carried by sap-sucking insect whitefly, CLCuD is the most severe disease affecting American cotton in the North Indian states of Punjab, Haryana, and Rajasthan, as well as in Pakistan. The disease has also been reported in China. The management of leaf curl disease is crucial for the sustainability of cotton production, especially in Asia,″ said Dr Gosal.

During the cotton season 2015-16, a severe epidemic of whitefly (locally knows as ″chitti makhi″) incidence was noticed in the northern region, especially Punjab, causing heavy losses to farmers. Consequently, many farmers shifted from cotton to water-guzzling paddy, putting stress on Punjab’s already-depleting groundwater resources.

Calling it a ″major breakthrough″ for cotton cultivation in the country, Dr Y G Prasad, Director, ICAR-Central Institute for Cotton Research (CICR), Nagpur, while speaking to The Indian Express, said that PAU’s work on developing virus-resistant breeding lines was ″a breakthrough for the region″ and something that ″takes a very long time to be achieved″.

″It is one of the examples of fine pre-breeding. We will be supporting and taking their work ahead for the commercial release after trials at multiple locations. Leaf curl disease is a serious problem for cotton farmers. The cross they have achieved takes a very long time to be successful. It will now be tested at multiple locations.

Once we have pre-breeding lines, scientists can further work on developing varieties which are resistant to multiple pests, including pink bollworm,″ said Dr Prasad.

Dr Prasad further said: ″We are already supporting PAU, and more funding will be provided for plant breeding and genetics work. CICR is the nodal institute for any great work that is done for cotton in the country and we will fast-track it. We are further going to fund them to study genetics and DNA of genes involved in this resistance and a research proposal will be prepared for the same.″

Explaining how the resistance has been achieved, Dr Dharminder Pathak, principal cotton breeder, PAU, said that related species and wild relatives of crop plants are rich sources of economically important genes. Consequently, PAU initiated a wide-hybridisation programme nearly 20 years ago to incorporate genes governing CLCuD resistance from wild cotton species into American cotton.

This challenging process, hindered by numerous pre- and post-fertilisation barriers, has now borne fruit. PAU has developed elite American cotton breeding lines carrying resistance to CLCuD, with the resistance genes transferred from the wild cotton species Gossypium armourianum.

″We had started working on this around 20 years ago. We primarily attempt crosses within the species but whenever we do not find any trait/gene of interest within cultivated species, then we look for particular trait in wild species and this is more so for stress-related traits such as disease resistance/insect pest resistance, etc.

The extant material has been developed for incorporating gene conferring resistance to the leaf curl virus. The CLCuD resistant cotton breeding lines will be commercialised after thorough evaluation in the multi-location trials. Pre-breeding lines will also be tested for tolerance against pink bollworm,″ said Dr Pathak.

Bhagirath Choudhary, founder director, South Asia Biotechnology Centre, Jodhpur, said: ″PAU’s research outcome is a significant scientific work to develop elite CLCuV resistance donor lines which will definitely complement the ongoing efforts by CICR and private cotton seed companies in the country. Post-2015 outbreak of cotton leaf curl virus (CLCuV) in North cotton growing zone and subsequent research by CICR mandates companies to evaluate cotton hybrids every year at six locations before they are recommended by CICR to respective state governments for commercial approval for planting based on CLCuD tolerance and minimum CLCuV threshold level.

Moreover, CICR and private seed companies have recently released commercial cotton hybrids derived from GVS 8 and GVS 9-resistant sources imported through NBPGR which are showing robust tolerance to CLCuV. In addition to developing good resistance donor line by PAU, what is desperately needed is to develop, evaluate and field test cotton lines resistant to devastating pink bollworm, Punjab agriculture department must issue timely NOCs for pending application for field trials of novel Bt genes and also deploy already-approved mating disruption technologies such as PBKnot to rebuild confidence of farmers in cotton in North India.″

Quoting the figures from International Cotton Advisory Committee (ICAC), Dr Ajmer Singh Dhatt, Director of Research, said that the three countries – India, Pakistan, and China – produce nearly half (49%) of the world’s cotton. Of the estimated 24.19 million global cotton farmers, approximately 85% (20.44 million) reside in these three Asian countries. Therefore, managing CLCuD is crucial for the sustainability of cotton production both in Asia and worldwide.

Dr V S Sohu, Head, Department of Plant Breeding and Genetics, PAU, said that the economic losses of around $5 billion were reported in Pakistan from 1992 to 1997, besides 40% reduction in cotton yield in India due to the virus. Beyond yield loss, CLCuD also adversely affects the quality of cotton fibre, the primary economic product of the crop.

Detailing the symptoms of CLCuD, Dr Pankaj Rathore, Principal Cotton Breeder and former director of PAU’s Regional Research Station in Faridkot, informed that it begins with the thickening of small veins on young leaves, leading to a continuous network of small veins. Other symptoms include the upward or downward curling of leaves, and in severe cases, the formation of cup-shaped outgrowths on the lower surface of leaves, resulting in stunted plants with fewer bolls.

He stressed that developing CLCuD-tolerant cotton varieties is the only viable option for managing this disease. Although several tolerant varieties have been developed in the past, new viral strains have rendered all existing varieties susceptible, including transgenic Bt-cotton hybrids.