Tungro-resistant Matatag rice varieties

By Sosimo Ma. Pablico

THE tungro virus disease is a very serious pest of rice such that it can cause heavy damages on standing rice crops. It is transmitted by green leafhoppers as they feed on the rice plants. That is if the insects have been feeding earlier on rice plants infected with the disease. 

When the population density of the nymphs in rice fields increases, the rice leaves turn yellow to orange as a result of heavy feeding. The leaves become mottled and the plant exhibit mild to severe stunting. Consequently, the plants do not develop well. Heavily affected farmers would be lucky if they would be able to recover their cost of production.

Although the average life cycle of rice leafhoppers is 20 to 30 days, several generations could occur in one season if uncontrolled and, hence, it is very difficult to predict severe infestations way ahead.
 

Thus far, the best method of combating the tungro virus disease is by planting rice varieties with intermediate resistance to the disease. Three varieties have been released already by the NSIC (National Seed Industry Council) for commercial planting. These are NSIC Rc118 (Matatag 3], NSIC Rc120 (Matatag 6), and Matatag 9 as a stop gap variety.

Bred by IRRI and developed into a variety by the PhilRice-led Rice Varietal Improvement Group (RVIG), Matatag 3 has a fairly early maturity (107 days when transplanted, 101 days when direct wet seeded). It grows to 94 cm when transplanted, but reaches 96 to 97 cm when direct wet-seeded. It produces 4,666 to 4,910 kg/ha when transplanted and 4,837 to 5,014 kg/ha when direct wet-seeded. Thus, it is suitable for both cultures.

Matatag 3 also possesses intermediate resistance to blast and bacterial leaf blight as well as moderate resistance to dead hearts, which are caused by stemborers. 

Bred by PhilRice, early maturing Matatag 6 matures in 90 to 92 days in both transplanted and direct wet-seeded cultures. When transplanted, it stands 109 to 110 cm at maturity. It is 103 cm tall when direct wet-seed.

Matatag 6 yields higher when transplanted (5,015 to 5,185 kg/ha) than when direct wet-seeded (4,657 to 4,839 kg/ha), which are fairly acceptable yields. It also possesses intermediate resistance to blast and bacterial leaf blight, moderate resistance to deadhearts and green leafhopper, and intermediate resistance to whiteheads or late attack of stemborers after panicle emergence.

Matatag 9, also bred by IRRI and then developed with the RVIG, derived its tungro resistance from a wild rice Oryza rupifogon and, hence, its tungro resistance is different from the genes present in other Matatag lines. It is resistant to rice tungro virus under the modified method of evaluation and intermediate under induced method.  In addition, it possesses intermediate reaction to blast, bacterial leaf blight, green leafhopper, and yellow stemborer.  It is also moderately resistant to whiteheads.

When transplanted, it yields 4,606 kg/ha during the dry season and 4,200 kg/ha during the wet season. Its maximum yield was 5,693 kg/ha. As direct wet-seeded crop, it yields 4,729 kg/ha during the dry season and 4,497 kg/ha during the wet season or an average 4,595 kg/ha across seasons.

It matures in 115 days after seeding and stands an average 102 cm at maturity. It produces 14 productive tillers in a hill.

(For past columns, click http://sundaypunch.prepys.com/archives/category/opinion/harvest-time/)

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