Agriculture Business Week

Climate Change is for real and it would lead to greater variability of rainfall, resulting in increased frequency of extreme events like flash floods, or more and longer dry spells due to high temperature.

Experts have predicted that at the worse, rainfall in 2050 will increase by 20 percent compared to the global average from 1961 to 1990 and the sea level will rise. This means that flooding would be the problem and not drought.

Even at present, typhoons are frequently occurring from July to December, bringing in strong winds and excess water that result in continuous flooding of rice fields. In the Philippines, 10 to 40 percent of the rice area during this period is damaged by flashfloods, especially in Nueva Ecija, Isabela, Cagayan, Pangasinan, Bulacan, Pampanga, Camarines Sur, Occidental Mindoro, Tarlac, and Nueva Vizcaya.

Almost all of the popular varieties cannot survive under prolonged submergence (more than three days), resulting in huge losses for the farmers. At the national level, production losses are estimated at an average of P2 million every year.

In the rainfed areas, which International Crops Research Institute for the Semi-Arid Tropics (ICRISAT ) Director General Dr. William, D. Dar calls “the hotspots of poverty, malnutrition, and child mortality,” climate change poses a grim picture of water scarcity and high temperature.

Aware of these conditions, researchers of the Philippine Rice Research Institute (PhilRice) are trying to find ways of mitigating the adverse effects of climate change.

SUBMERGENCE TOLERANCE
PhilRice Executive Director Dr. Leocadio S. Sebastian said that included among the activities being done by the Institute is the development of a variety that could withstand complete submergence for at least two weeks. PhilRice researchers conduct their own breeding work as well as collaborate with the International Rice Research Institute (IRRI) scientists in the adaptation and dissemination of promising submergence tolerant lines, including the IRRI line IR 64-Sub 1, which contains the Sub 1 gene from the Indian variety FR13A, and is claimed to survive under water up to two weeks.

At PhilRice Midsayap in North Cotabato, Jonathan M. Niones, a senior science research specialist, has come up with a line that can withstand continuous submergence up to 28 days. Tagged as PR33395-27-1-B-B-B, this Tainted advance elite line is a cross of Malay I and Matatag 1. Malay I is an advance upland breeding line, while Matatag I is a rice tungro-resistant and irrigated lowland variety.

PhilRice’s submergence tolerant line was named Raeline 10, which stands for rainfed advance elite line. Raeline 10, according to Niones, is tungro-resistant and early maturing (105 days), has intermediate resistance to bacterial leaf blight, has moderate to shatter ability, and its eating quality is comparable to IR 64.

Results of two Midsayap screen house tests in cemented ponds in 2006 and 2007 showed that Raeline 10 had a 100 percent plant survival in 21 days of submergence. In contrast, the IRRI line IR 64-Sub 1 only had 75 percent survival, while SwarnaSub 1, which was found earlier to survive complete submergence in northern Bangladesh, did not survive extended submergence.

In the same screen house tests of Niones, the original IR 64 had 50.5 percent survival at 21 days of submergence, while IR 36 and IR 45 had 75 percent like IR 64-Sub 1. PSB Rc68 also had 75 percent survival, while PSB Rc18 had 50 percent.

In a field adaptation trial set up on October 15, 2007 in Brgy. Bulucaon, Pigcawayan, North Cotabato to demonstrate the PhilRice and IRRI lines, a large percentage of the Raeline 10 plants survived 28 days of continuous submergence under water, while IR 64-Sub I was almost wiped out.

Under irrigated lowland conditions at PhilRice Midsayap, Raeline 10 yielded 4.38 t/ha, a little lower than Raeline 4 (4.67 t/ha), drought-tolerant Raeline 3 (4.58 t/ha), and Raeline 9 (4.40 t/ha).

PhilRice scientists at the Institute’s Central Experiment Station in Maligaya, Science City of Munoz, Nueva Ecija are also collaborating with IRRI scientists primarily on the evaluation and adaptation of lines available at IRRI with submergence tolerance, which are available at IRRI, as well as on the multiplication and distribution of the seeds. The project also includes loss and risk assessment, development of a response plan, training programs for extension workers in the national research and extension system, and a follow-up study.

Dr. Nenita Desamiro, team leader of the PhilRice team, is being assisted by Dr. Norvie L. Manigbas, Thelma Padolina, Niones, and Ofelia Malonzo.

The PhilRice team started in July 2007 to screen nine elite lines and six lines derived from anther culture for submergence tolerance, Dr. Manigbas said. The elite lines were IR 64-Sub 1, FR13A, Swama-Sub 1, Samba Mahsuri, IR 42, IR 64, PSB Rc68, PSB Rc82, and NSIC Rc 146. The plants were submerged for 12 days at 30 days after transplanting with murky and cloudy water from the irrigation canal and nearby fields. Dr. Manigbas said none of the entries survived 12 days of submergence.

In a second screening consisting of two batches in October and November 2007, the submergence tolerant lines IR 64Sub 1, FR13A, and Swarna-Sub 1, Samba Mahsuri survived after 10 days of continuous flooding. The PhilRice lines derived from anther culture also showed tolerance to submergence.

Aside from screening, the PhilRice researchers will also try to determine the best management practices that should be followed after submergence.

HEAT TOLERANCE
Among the possible impact of temperature rise by about 1 C would be increased heat stress on crops, higher night time temperatures that could adversely affect grain formation, possible decline in rainfall in some regions, and increased evapo-transpiration rates as a result of higher temperatures, according to reports.

To help mitigate the effects of higher temperatures caused by climate change, Dr. John de Leon, chief science research specialist of PhilRice, is trying to identify rice lines or germplasm that can complete their flowering in rainfed areas before noon when heat stress is at its peak. He said heat affects anthesis or the date and time when the pollen grains shed. Higher temperatures make the shedding of pollen grains difficult because these become sticky for reasons that are not yet known. One thing is sure: Heat produces sterile grains.

In a collaborative study with IRRI scientists, a study on heat-tolerant lines was set up simultaneously at PhilRice and IRRI in the 2007 dry season. Some 157 varieties from Philippines, Pakistan, Iran, Africa, and Nepal that are stored in the IRRI genebank were used in the experiment. Based on reports, these varieties have heat tolerance of varying degrees.

Dr. Manigbas said planting was done so that flowering would coincide with the hottest period of the year-third week of April to the second week of May. Among the data collected were flowering date and anthesis. Pollen staining was also done to determine the sterility or fertility of the pollen grains.

Of the 157 varieties, 56 were frilly fertile despite the heat and, hence, were selected for the 2008 dry season set up: Five direct seeding dates were followed so that flowering would coincide with the hottest period – January 13, January 24, February 2, February 14, and February 26.

In doing so, PhilRice and IRRI scientists are hoping to identify varieties that could either avoid or tolerate heat stress.

At the moment, nothing is definite yet but the prospects on the immediate mitigation of climate change impact are bright even if the greater challenges are way ahead. Likewise, PhilRice and IRRI scientists, are crossing their fingers on highly favorable results of their efforts.