The newest transgenic cotton cultivar developed by Embrapa - BRS 500 B2RF - combines high productivity with resistance to the main diseases, with emphasis on ramularia spot and root-knot nematode, two serious problems faced by cotton farmers today.
Ramularia spot, caused by the fungus Mycosphaerella areola, It is currently considered the main cotton disease in the country, requiring around eight fungicide sprays per harvest on cultivars most susceptible to the pathogen. The root-knot nematode (Meloidogyne incognita) is a difficult disease to control. The pest parasitizes the roots of several crops and in cotton compromises cotton plume productivity by up to 40%. The best method of controlling nematodes is the use of resistant or tolerant crops and cultivars.
An alternative for managing these problems, BRS 500 B2RF, is recommended for cultivation in the Cerrado region, where the occurrence of ramularia spot is prevalent, or in areas with incidence of root-knot nematode. Recent surveys carried out in the two main cotton-producing states detected infestation with this nematode in 25% of the areas sampled in Mato Grosso and in 37% in Bahia. The data comes from the Instituto Matogrossense do Algodão (IMAmt), Embrapa Algodão, Fundação Bahia, Associação Baiana dos Produtores de Algodão (Abapa) and Instituto Brasileiro do Algodão (IBA).
“In 27 trials conducted in the Cerrado environment in the 2017/2018 and 2018/2019 harvests, the BRS 500 B2RF cultivar had a minimum severity of ramularia spot, demonstrating the stability of this characteristic”, says the researcher responsible for obtaining the cultivar, Nelson Suassuna.
He explains that the fact of not requiring fungicide applications to control ramularia spot implies a reduction in production costs and represents an environmental gain. “It is not uncommon for eight fungicide applications to be carried out per harvest to control the disease in susceptible cultivars, at a cost of more than R$100,00 per application per hectare. Considering the national area cultivated with cotton, the adoption of this technology can bring substantial gains,” he says. “Partial resistance to root-knot nematode also gives producers security in infested areas, avoiding losses associated with this pathogen,” he adds.
In addition to high resistance to ramularia leaf spot and partial resistance to root-knot nematode, the BRS 500 B2RF cultivar is also resistant to the main crop virus in Brazil, known as typical blue disease, and angular leaf spot.
Associated with multiple disease resistance, the cultivar still presents good agronomic performance. The average productivity obtained in 27 locations was 5.667 kilos per hectare of seed cotton and 2.579 kilos per hectare of fiber. In the last harvest, the average productivity of seed cotton in the Cerrado was 4.287 kg/ha and 1.802,11 kg/ha of fiber, according to data from the Brazilian Association of Cotton Producers (Abrapa). BRS 500 B2RF also has desirable fiber quality for the textile industry, with average fiber length values of 30,4 mm (average fiber); micronaire index of 4,6 and fiber strength of 30,8 gf.tex-1.
The new cultivar relies on technology Bollgard II Roundup Ready Flex (B2RF, from Bayer), which provides resistance to some lepidopteran pests (caterpillars) and tolerance to the herbicide glyphosate at all stages of crop development.
It took more than a decade of research to combine all these characteristics into a single material. Researcher Camilo Morello, leader of Embrapa's cotton improvement team, recalls that in 2004 studies began to identify sources of resistance to ramularia spot and nematodes. From these sources, the resistant conventional cultivar BRS 372 was obtained in 2014, providing complete resistance to ramularia leaf spot and partial resistance to root-knot nematode for the BRS 500 B2RF cultivar.
“There were intense years of research to find sources of resistance, understand the inheritance of resistance and develop molecular markers to assist in the selection process. Finally, transgenic technologies [FRdC1] were introduced to assist in the management of invasive plants and insect pests, Roundup Ready Flex(RF) and Bollgard II (B2), respectively, with the generation of populations, selection of plants and progenies, testing of lineages in different environments, until we arrive at the cultivar”, reports Morello.
The BRS 500 B2RF will be available to producers in the next harvest, according to the head of Technology Transfer at Embrapa Algodão, João Henrique Zonta. The company licensed to sell the seeds is IST Cotton Brasil Ltda., which is carrying out actions to publicize the cultivar. “This year we should harvest around nine tons of genetic seeds, which will enable the production of basic seeds to supply the market from the next harvest onwards”, he states.
Receive the latest agriculture news by email
Receive the latest agriculture news by email
