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Agriculture

The menu for next few years

Specialists predict a decline in the number of new diseases and plagues – and the related emergencies - resulting from climate change diseases

The Face project, in Jaguariúna: coffee plants enriched with CO2 are taller

EDUARDO CESARThe Face project, in Jaguariúna: coffee plants enriched with CO2 are tallerEDUARDO CESAR

Specialists are networking to predict the possible effects of climate changes on agribusiness, which accounts for one third of Brazil’s GDP. There are signs indicating that the production of soya, wheat, and other crops may decline dramatically and the incidence of diseases may rise, as a reaction to the probable increase in temperature and changes in rainfall distribution throughout the country. The fear is that prices will go up and the variety of grains, vegetables and fruit will decrease. In anticipation of scenarios that predict harsh times ahead, research centers and companies are developing and introducing varieties of grains and vegetables that are more resistant to high temperatures and to attacks from organisms that cause diseases and plagues. The tendency is that plants, pests, consumers and also the economy will readjust and rebalance.

A study funded by the World Bank enabled researchers from the State University of Campinas (Unicamp) and from the Brazilian Agricultural Research Corporation/Embrapa’s Agricultural and Animal Husbandry Infotech to use 23 computer simulated models related to the global climate and to three regional climates. These simulations detected a clear tendency for cotton, rice, bean, soybean, wheat and corn yields to drop as an effect of the probable rise in temperature from 2020 to 2030. This drop may correspond to 64% in the case of beans, and to 41%, in the case of wheat, even from the most optimistic point of view, where the annual mean temperature goes up insignificantly. From a pessimistic point of view, the yield of beans may drop by 70% and soybeans, by 24%. According to this study, only sugarcane and pastures will benefit from a warmer climate.

Concurrently, specialists from Climapest, a research project coordinated by Embrapa Meio Ambiente, in the town of Jaguariúna, has identified that some diseases – especially those caused by fungi – and pests may increase in many of the 19 crops analyzed in the project. These crops – which include soybeans, corn, coffee, rice, beans, bananas, mangoes and grapes – will be affected by higher levels of CO2 in the air, by warmer temperatures and stronger ultraviolet B radiation, as predicted in climate change scenarios (see table).

Another possible consequence is the migration of diseases such as the black sigatoka, caused by a fungus that destroys banana plantations. Specialists believe that the disease will decline in some banana-producing regions and will migrate to the south, where no incidence of this fungus has been seen yet. “The battle against these diseases is endless,” says Wagner Bettiol, of Embrapa Meio Ambiente. “The plants and the plagues in the upcoming decades may be different from the current ones.”

040_Pragas_198-1AThe prediction is that the incidence of some diseases may increase and others may decrease. “But it’s impossible to generalize what will happen,” says Raquel Ghini, a researcher at Embrapa in Jaguariúna and coordinator of the Climapest project. Created three years ago thanks to a R$ 5 million investment from Embrapa and R$ 2 million from other public and private institutions and companies, the project brought together 134 researchers from 17 Embrapa units and 22 research institutes and universities and is expected to result in a book – scheduled for publication by the end of the year – with maps indicating the probable distribution of agricultural diseases and plagues in Brazil in the upcoming decades.

“A warmer climate drives the proliferation and reproduction of insects,” says José Parra, a professor at the Luiz de Queiroz School of Agriculture (Esalq) of the University of São Paulo (USP). Parra is also the coordinator of the biological control of plagues department at the National Science and Technology Institute. He adds that “the damage depends on interaction with other insects and with the environment, on the reactions of the plants, and on the water supply.”

According to him, natural enemies might develop faster and control the plagues. “If the geography of the crops changes, as could happen in the case of citrus fruits, the plagues might change and those that are more resistant to high temperatures will prevail,” he says.

Visible effects
“We have clearly seen that the number of coffee plantations has dropped significantly and actually disappeared in the northwest region of the State of São Paulo and in the southern region of the State of Minas Gerais. These regions have been affected by rising temperatures in the last few decades,” says Hilton Silveira Pinto, a researcher at Unicamp and one of the coordinators of the study funded by the World Bank. Previous studies indicated that the availability of land for coffee crops will drop by nearly 90% in the regions suitable for the planting of coffee in the states of Goiás, Minas Gerais and São Paulo and by 75% in the state of Paraná by 2020, as a result of rising temperatures. Coffee will most likely continue to be planted only in the highlands of the southeast or further down south, including the state of Rio Grande do Sul, where today coffee is only consumed. “Climate change is already changing the transportation and distribution networks and rural organization, the result of unemployment or the migration of skilled labor.”

The increase in carbon gas (CO2) levels in the air might have a positive effect, in the sense of increasing crop yields and making plants grow faster. Embrapa in Jaguariuna is conducting an experiment called FACE – the acronym for free air carbon dioxide enrichment – in which the coffee plants enriched with extra doses of CO2 grew taller and are now as tall as those planted a year before that were nourished by the CO2 found in the atmosphere.

040_Pragas_198-1BThe Face experiment which started in August 2011 is being conducted on 6.5 hectares of land planted with coffee. Twelve octagons with 10-meter diameters stand out in the midst of these plants. The coffee plants on six of the octagons are enriched with CO2 with a concentration of 550 parts per million (ppm), simulating the atmosphere at the end of the century. Every day, sensors automatically activated according to the direction and strength of the wind release 600 kg of the gas onto the plants. The carbon gas comes out of a 10-meter tank. The coffee plants on the other six octagons only get the CO2 from the atmosphere, with a concentration of 400 ppm –higher than the 350 ppm that Raquel used 10 years ago to predict plant behavior. “Ten years ago, nobody believed anything being said about climate change,” she says.

The accelerated growth of plants can also be a problem. In the last two years, flower growers in the town of Holambra noticed that the plants flowered earlier than expected, because of the increase in the region’s mean temperature. In this case, accelerated growth is a tragedy for flower suppliers who must deliver fresh flowers into the hands of consumers on special dates, such as the eve of Mother’s Day or during All Souls’ Day.

At Embrapa Semiárido in the city of Petrolina, state of Pernambuco, Francislene Angelotti has conducted a number of tests in open greenhouses. She noticed that the main fungi-caused diseases that damage grapes – mildew, powdery mildew, and plant rust – react differently to the increase in CO2 concentrations. Differences were also found according to the grape variety. The Sugraone variety proved to be more sensitive to rust, whereas the Crimson variety was more sensitive to the fungus that causes the powdery mildew on the grape vines. On the other hand, mildew was less aggressive to the Italia variety. As happened in the case of the grapes, the incidence of the fungus that causes powdery mildew on tomatoes, lettuce, bell peppers, and melons will probably be higher, due to higher temperatures and humidity. The fungus that causes mildew on lettuce and at present only thrives in cooler temperatures and lower humidity, will probably become less recurrent in a warmer, drier climate.

040_Pragas_198-2However, specialists warn that the disease-causing agents can adapt or come out of the shade, taking up the space left by other agents. The Pseudoperonospora cubensis, a microorganism that causes mildew in pumpkins, melons, lettuce and zucchini, usually dies when temperatures go up. Apparently, the microorganism has already adapted itself to a warmer, drier climate.

“Mildew has become a common disease in the north of the state of Minas Gerais, because the fungus has already adapted itself to a warmer climate,” says Kátia Regiane Brunelli, a researcher at Sakata Seed Sudamerica Ltda., a Japanese corporation that develops and produces genetically improved vegetable seeds. “Since the climate tends to become warmer and drier,” says Romulo Fujito Kobori, the company’s director of research and development, “some virus-caused diseases might become more prevalent than they are nowadays.”

Alternative varieties
Soon after his conversations, seven years ago, with the team from Climapest on the diseases most likely to prevail in the forthcoming years, Kobori and his team of geneticists began to intensify the search for varieties that are more resistant to climate changes. A visit to the greenhouses and to the vegetable plots at the company’s experimental station in the city of Bragança Paulista attests to the fact that the work has matured for most of the vegetables subject to genetic improvements: “In 20 years, if the climate changes significantly, this variety of broccoli won’t be any good, but this other variety will do well,” he says, pointing to the vegetable plots in front of him. The vegetable plots are planted with broccoli and tomatoes with subtle yet decisive differences in terms of size, shape, thickness of the leaves, and the capacity to survive diseases.

Some years ago, Sakata began to sell tomato, lettuce, bell pepper, melon, carrot, onion, pumpkin, zucchini and cucumber varieties that had become genetically resistant to fungi, viruses and bacteria expected to proliferate significantly in tropical regions in the upcoming years. This is long-term work: each new variety needs 10 to 15 years of work until it becomes commercially feasible. Kobori hopes that molecular biology techniques will cut this time by half, by identifying the plants with the genes that have the characteristics of interest, such as quality, productivity, and resistance to diseases.

The genetic selection of new varieties of fruit trees takes even longer. “The varieties we are using are 60 years old,” says Renato Bassanezi, a researcher at the Fundo de Defesa da Citricultura (Fundecitrus), a research center funded by citrus fruit growers from the city of Araraquara. Orange trees that are more resistant to climate change would be most welcome because climate change is already interfering in citriculture, one of the major economic activities in the State of São Paulo. The state is the leading Brazilian producer of oranges and one of the biggest such producers in the world. 230 million orange trees are currently being cultivated in the state.

The Podosphaera xanthii, which causes powdery mildew, growing on the leaves of a cucumber plant: one of the likely hazards that will have to be dealt with in the future

EDUARDO CESARThe Podosphaera xanthii, which causes powdery mildew, growing on the leaves of a cucumber plant: one of the likely hazards that will have to be dealt with in the futureEDUARDO CESAR

In 2009, unexpectedly heavy rains in the orange growing region jeopardized the flowering season and triggered the growth of fungi; the crop yields went down by 10%. According to Bassanezi, the orange growers purchased fungicides, which proved to be unnecessary, because the weather was dry in the following year. Nearly 20 days of steady rainfall in early June this year is expected to lead to early flowering, which will again trigger the growth of weeds, fungi, and disease-transmitting insects.

Citrus canker, a widespread, bacteria-caused disease that proliferates easily, may become more serious in a climate whose average yearly temperatures are high and rainfall is heavy and concentrated. “If the predictions on climate change are confirmed,” says Bassanezi, “the country’s north and south regions will become more susceptible to citrus canker epidemics.”

Germplasm banks
If plagues and diseases become more prevalent, the germplasm banks – organized collections of rice, bean, soybean, corn and other plant varieties of economic interest maintained in refrigerated rooms or in the field – will become increasingly important. The current state of the germplasm banks is not good, because there is no updated inventory of the collections, which are housed at research centers, universities, botanical gardens, and companies.

“The collections of less than 10% of the germplasm banks are properly described,” says José Baldin Pinheiro, a professor at Esalq and president of the Paulista genetic resources network, created in March this year. At a meeting to be held in the city of Piracicaba at the end of this month, the members of the network will present updated information on the collection and the state of conservation of the germplasm banks in the State of São Paulo.

It is possible that many plants that will comprise agriculture in the future are already being cultivated in the northeast of Brazil. In November 2006, Francislene moved from the state of Parana to the city of Petrolina. At that time she had already marveled at how resistant the region’s plants were to drought and at their power to regenerate. During the drought, the plants looked as if they had been burnt by fire; two weeks after heavy rainfall, they began to flourish again.

A few months ago, Francislene tasted the apples, pears, and Japanese persimmons grown in Embrapa’s experimental fields and was quite surprised. “The pear varieties cultivated at the Agronomy Institute of Campinas and the apple varieties cultivated at the Agronomy Institute of Parana adapted very well,” says Paulo Coelho Lopes, coordinator of the crop diversification project conducted at the Embrapa Semiárido unit. “Nobody had ever believed that fruit grown in a temperate climate could flourish here.”

The Projects
1. The effect of global climate change on plant diseases (nº 04/01966-7); Modality Regular Line of Funding for Research Project; Coordinator Raquel Ghini – Embrapa Meio Ambiente; Investment R$ 61,151.03 (FAPESP)
2. Climapest; Modality Embrapa Macroprogram; Coordinator Raquel Ghini – Embrapa Meio Ambiente; Investment R$ 5,028,798.47 (Embrapa)

Scientific article
GHINI, R. et. al. Climate change and diseases of tropical and plantation crops. Plant Pathology. v. 60, n. 1, p. 122-32. 2011.

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