In its fight against pathogens, mustard can get some help from chickpea. Indian scientists studying a fungal pest that causes extensive damage to mustard and rapeseed crops found that the rabi pulses crop has an in-built mechanism in its genes to ward off the fungal attack, which they hope could someday come to the help of the important oilseed crop of India.
Researchers from the National Institute of Plant Genome Research (NIPGR), New Delhi, and Assam Agricultural University in Jorhat, led by NIPGR plant biologist Muthappa Senthil-Kumar, are looking for a better way to manage blight, a plant disease caused by fungus Alternaria brassicae, which can lead to a crop damage of up to 47 per cent in mustard. The pest also affects a variety of other crops, including cabbage, broccoli and cauliflower.
On an average, India grows mustard and rapeseed over an area of 6.18 million hectares with an annual production of 7.36 million tonnes, making it one of India’s main oilseed crops along with soyabean and groundnut.
It is said that the area under cultivation in India infected by Alternaria is nearly 2.97 m ha per year, if the climatic conditions are favourable for disease. In a bad year, the loss can be as high as 3.4 million tonnes.
Drastic drop in yield
Studies in the past have shown that the yield in a field infected by fungus Alternaria brassicae can come down by as much as by 47 per cent, if remedial measures are not taken.
“But the losses in Rajasthan and Uttar Pradesh, where mustard is grown in huge quantities, are lower these days as farmers are more aware and apply fungicide during early days of infestation. However, the problem is severe in States like Assam where the crop was introduced later,” said Senthil-Kumar.
“Since mustard plant’s wild relative varieties do not have a resistance mechanism to fight the fungus, plant breeders all over the world were not able to develop rapeseed mustard varieties that are blight-resistant through conventional breeding or modern biotechnological approaches. Highly infectious, this fungus can infect the host plant at all stages of growth. As a result, it is currently controlled through chemical fungicides,” Senthil-Kumar told BusinessLine.
The NIPGR scientists, who worked with Assam Agricultural University researchers, quite accidentally stumbled upon chickpea plants which, despite being in an adjoining plot to an Alternaria-infected field, remained unaffected. The team, comprising Senthil-Kumar, his NIPGR colleague Urooj Fatima and AAU scientist Priyadarshini Bhoralim reported their findings in the journal Molecular Plant-Microbe Interactions recently.
Such plants are normally called non-host plants as they resist the pest’s attempt to destroy them. “We came across several crops that can do this to Alternaria, but chickpea was more efficient in doing it,” said Senthil-Kumar.
According to him, non-host resistance (NHR) is the most durable resistance against fungal pathogens. While Alternaria typically penetrates the epidermis or the stomata of a host plant, this is unable to deploy this attack on plants protected by NHR. To protect mustard crops from this fungus, scientists are studying the mechanisms of NHR in order to develop improved crop varieties.
The Indian scientists found that the chickpea actively suppressed the fungal development, penetration, and colonisation even after hours of infection. They also studied chickpea transcripts to pinpoint several genes involved in the plant’s pathogen defence.
“These genes are interesting candidates for additional study to determine their precise involvement in NHR,” said Senthil-Kumar, adding that these genes could then be transferred to mustard plants to develop blight-resistant crops.