India: Meeting pesticide residue challenge in basmati – by breeding for resistance

Pesticide residues are an issue, more so when it concerns products such as basmati rice, fetching the country annual export revenues ranging from $ 3.23 billion in 2016-17 to $ 4.52 billion in 2014-15. The burden of consignments being rejected ultimately falls on the farmer, who has to, then, use new-generation pesticides that are safer, but costlier and very often proprietary/patented molecules.

The most recent example is of Tricyclazole. A single 120-gram spray of this common fungicide, against leaf and neck blast disease in paddy, hardly costs Rs 150-170 per acre. But with the European Union (EU) deciding not to allow import of any rice having Tricyclazole levels above 0.01 parts per million (ppm) from January 1, farmers would find it difficult to spray the generic chemical sold under assorted brands like ‘Sivic’, ‘Baan’ and ‘Beam’. The existing tolerance limit stipulated by the EU (which accounts for about 3.5 lakh tonnes of India’s total annual basmati shipments of 40 lakh tonnes) for Tricyclazole is one ppm or 1 mg/kg; 0.01 ppm will make it 1mg/100 kg!

With Tricyclazole ruled out, farmers may, henceforth, have to go for fungicides that are considered environmentally friendlier, though costing ten times more. These include Azoxystrobin (a single 200-ml spray, sold under the Swiss company Syngenta’s ‘Amistar’ brand, costs around Rs 900 per acre) and Picoxystrobin (the cost of a single 400-ml spray of this formulation, sold under DuPont’s ‘Galileo’ brand, comes to Rs 1,300 per acre). No less expensive is ‘Nativo’. This combination fungicide of Bayer CropScience, containing Tebuconazole and Trifloxystrobin, costs Rs 1,000 for a single 160-gram spray per acre.

However, an alternative approach to pesticide application — necessary, especially keeping in view basmati’s premium quality attributes and huge export market — is to “breed for disease resistance”. This involves transfer of specific disease-resistance genes, from both traditional landrace cultivars and wild relatives of paddy, into existing high-yielding basmati varieties. That is what scientists at the Indian Agricultural Research Institute (IARI) have sought to do.
The New Delhi-based institute — under a collaborative project with the Indian Council of Agricultural Research’s National Research Centre on Plant Biotechnology — has transferred the ‘Pi9’ gene into its popular Pusa Basmati-1 variety. This gene, sourced from Oryza minuta (a wild relative of Oryza sativa, which is the normal cultivated paddy), provides “very high resistance” against leaf blast and “moderate resistance” against neck blast fungus.

The resultant variety, which is called Pusa Basmati-1637, combines Pusa Basmati-1’s high-yielding trait with resistance against a fungus that infests the leaf and neck nodes of the rice plant’s main stem, from where the grain-bearing earheads (panicles) emerge. Blast disease affecting the leaf basically damages the chlorophyll, thereby impeding photosynthesis that involves absorption of sunlight and using its energy to synthesise carbohydrates. Neck blast, if severe, can cause the stem to even break. If the panicles at that point have only partially formed grains, in their early milky stage, the yield losses can be huge.

Rajeev Kharb, a farmer from Tito Kheri village in Safidon tehsil of Haryana’s Jind district, has grown Pusa Basmati-1637 in five out of his total 80-acre holding. The latter includes 28 acres of own and 52 acres of leased land. High temperatures and humidity levels this time round has resulted in the bulk of his planted area – mainly under Pusa Basmati-1401, Pusa Basmati-1 and Pusa Basmati-1509 – suffering gardan-marod (the local term for blast, whose literal translation is “curling of the neck”) to the extent of 10-20 per cent.

“But nothing has happened to my Pusa Basmati-1637 field. This, even without spraying any Tricyclazole,” says Kharb. A loss of 10-20 per cent isn’t small. Taking per-acre yields of 22-25 quintals for Pusa Basmati-1, 25-28 quintals for Pusa Basmati-1509 and 28-30 quintals for Pusa Basmati-1401, and current average price realisations of Rs 2,800/quintal, it works out to anywhere from Rs 7,000 to Rs 14,000 per acre.

“We will continue to have to spray for other diseases (bacterial blight and sheath blight fungus) and pests (brown plant hopper and stem borer). But with this new variety, there is still significant savings from not using Tricyclazole or other expensive fungicides against blast,” points out Pritam Singh Hanjra, a progressive farmer from Urlana Khurd village in Madlauda tehsil of Panipat district.

Hanjra, who has sown Pusa Basmati-1637 in five out of his 105-acre holding (30 acres own and the rest leased), estimates expenses on crop protection chemicals at Rs 3,000-4,000 out of the total cultivation costs of Rs 20,000-22,000 per acre for paddy. “It can go up, depending on the extent of pest and disease incidence. Either way, this is the second biggest expenditure head after manual harvesting-and-threshing (Rs 4,500-5,000), and more than fertilizers (Rs 2,100-2,200),” he claims.

A K Singh, head of IARI’s Division of Genetics, notes that Indian breeders have, over a period, managed to raise crop yields. The traditional tall basmati cultivars, for instance, gave barely 8-10 quintals of paddy per acre. With improved dwarf high-yielding basmati varieties, these have gone up to 25 quintals or so. “Our challenge now is to protect these yields and preferably through breeding for resistance, as opposed to pesticide application,” he adds.
IARI is, in fact, working on transferring other blast resistance genes as well — such as ‘Pi54’, ‘Pi25’, ‘Pi2’ and ‘Pib’, all from wild relatives and land races of rice — to high-yielding basmati varieties.

“We want to do pyramiding of these genes (combining two or more of them), in order to impart more durable resistance against blast. Besides, we have already developed and released two new varieties, Pusa Basmati-1718 and Pusa Basmati-1728, both of them incorporating the Xa21 and xa13 genes that confer resistance to the bacterial blight pathogen. The first variety is basically Pusa Basmati-1121 and the second one Pusa Basmati-1401, containing both these genes obtained from Oryza longistaminata (another wild relative of paddy) and BJ1 (a traditional land race), respectively,” informs Singh.