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varieties and did not seem to exert special selection pressure on current RTSV populations.Because of the presence of mixed infections and minor genotypes, however,our data suggest that the structure and composition of the virus population may changeif a different selection pressure such as a host or environmental shift occurs. It istherefore essential to monitor virus populations when virus-resistant varieties are deployed.ReferenceYambao MLM, Cabauatan PQ, Azzam O. 1998. Differentiation of rice tungro spherical virusvariants by RT-PCR and RFLP. Int. Rice Res. Notes 23(2):22-24.NotesAuthors' address: K.M.L. Umadhay, M.L.M. Yambao, and O. Azzam. International RiceResearch Institute, MCPO Box 3127, Makati City 1271, Philippines.Citation: Chancellor TCB, Azzam O. Heong KL. editors. 1999. Rice tungro disease management.Proceedings of the International Workshop on Tungro Disease Management, 9-11November 1998, IRRI, Los Baños. Philippines. Makati City (Philippines): InternationalRice Research Institute. 166 p.Preliminary analysis 21
Breeding for rice tungro disease resistanceat PhilRiceL.S. Sebastian, E.R. Tiongco, D.A. Tabanao, G.V. Maramara, S. Abdula, and E.B. TabelinBreeding for resistance to rice tungro disease is a major objective of therice breeding program for irrigated lowland and rainfed ecosystems at thePhilippine Rice Research Institute. Tungro-resistant donors are identifiedusing visual screening and serological assays and are then crossed withselected high-yielding modern genotypes with good grain quality. Field evaluationof advanced breeding lines is carried out at experimental stations inNueva Ecija and in North Cotabato. Methods for generation advance andresistance screening are described. As of the 1998 wet season, several F8lines from the following crosses showed good resistance to tungro: PSBRc4 x TI-11-8, BPI Ri10 x TI-11-8, IR64 x TI-11-8. Molecular markers arecurrently being used to map resistance genes to tungro from Utri Merahand Utri Rajapan and molecular techniques are being developed to characterizestrains of rice tungro spherical virus.The development of tungro-resistant varieties remains a primary concern in the Philippinesbecause tungro is still the most destructive rice virus disease in the country.Almost all resistant varieties so far developed and released are resistant to the insectvector ( Nephottetix virescens ) only. A few varieties have resistance to rice tungrospherical virus (RTSV). Chemical control against the vector is very costly and thedisease can still occur even if the vector population is not high. Furthermore. there isno effective chemical control measure against tungro viruses. As such, the developmentof varieties resistant to this disease is a priority objective of the Philippine ricebreeding program.Rice tungro disease concerns at PhilRiceBreeding for yield and grain qualityThe breeding program for irrigated lowland (transplanted and direct-seeded) andrainfed rice ecosystems in the Philippine Rice Research Institute (PhilRice) has alwaysincluded tungro resistance as an objective. Selection for desirable plant morphologyand grain structure starts at F 3 . Segregating generations are advanced withcontinuous selection for yield, grain quality, and other important traits. Resistance toimportant insect pests and diseases is incorporated by crossing selections with highyield and good grain quality with breeding lines and traditional accessions carryingthe desired resistance traits. For tungro resistance, the most widely used materials areTI-11-8 (a BC4Fn derived from ARC11554 × TN1) and Utri Merah. To screen for ricetungro disease (RTD) resistance specifically, lines advanced from these crosses areshuttled to Midsayap, North Cotabato, where tungro incidence is consistently higheven during the dry season. Each entry is observed for visual symptoms caused by thedisease. Lines found to have some amount of resistance are included in multilocationpreliminary and advanced yield trials for further and final-stage tests. This method ofselection for tungro resistance, however, usually results in the selection of lines thatare resistant only to the vector.
Page 2 and 3: RiceTungro DiseaseManagementEdited
Page 4 and 5: ContentsRice tungro disease in the
Page 6 and 7: ForewordThe intensification of rice
Page 8 and 9: PrefaceProviding farmers with optio
Page 10 and 11: Rice tungro disease in the Philippi
Page 12 and 13: Cotabato, and Laguna) during 1995-9
Page 14 and 15: seed growers and farmers to increas
Page 16 and 17: Fig. 2. Incidence of rice tungro di
Page 18 and 19: De los Reyes JB, Cabunagan, RC, Col
Page 20 and 21: Preliminary analysis of genetic var
Page 22 and 23: Fig. 2. Distinct rice tungro bacill
Page 24 and 25: Fig. 4. Dendogram depicting the rel
Page 26 and 27: Preliminary analysis of genetic var
Page 28 and 29: Table 1. Size characteristics of th
Page 32 and 33: Developing breeding lines with RTD
Page 34 and 35: In CES, 28 entries had low tungro i
Page 36 and 37: Table 2. Best rice tungro disease-r
Page 38 and 39: Breeding for rice tungro virus resi
Page 40 and 41: Table 2. Promising lines resistant
Page 42 and 43: Table 4. Rice cultivars used as hyb
Page 44 and 45: Shahjahan MB, Jalani S, Zakri AH, I
Page 46 and 47: Table 1. Initial 19 transgenic line
Page 48 and 49: Table 4. Percent infection of trans
Page 50 and 51: very low level. In fact, transgene
Page 52 and 53: of Agricultural Research (ICAR). Pr
Page 54 and 55: Fig. 2. Mean infection with rice tu
Page 56 and 57: (RTBV) and rice tungro spherical vi
Page 58 and 59: Table 4. Percent infection a with r
Page 60 and 61: GLH numbers were much lower on IR62
Page 62 and 63: Cabunagan RC, Hibino H, Sama S, Riz
Page 64 and 65: Prospects of virus-resistant variet
Page 66 and 67: Tungro in Bali (1987-97)Tungro infe
Page 68 and 69: Fig. 5. Proportion of varieties gro
Page 70 and 71: Table 3. Percent incidence of rice
Page 72 and 73: Evaluating rice germplasm for resis
Page 76 and 77: Rice tungro disease resistance andm
Page 80 and 81:
ecommended vector-resistant variety
Page 82 and 83:
Materials and methodsBatches of ant
Page 84 and 85:
ReferencesClark MF, Adams AN. 1977.
Page 86 and 87:
(e.g., Sokal and Rohlf 1995, p 213;
Page 88 and 89:
Surveillance scheme for tungro fore
Page 90 and 91:
entrusted with implementing the pro
Page 92 and 93:
Table 1. Number of mobile nursery t
Page 94 and 95:
are implemented immediately. The co
Page 96 and 97:
Farmers’ rice tungro managementpr
Page 98 and 99:
Experience with tungroAlthough both
Page 100 and 101:
Table 5. Farmers (%) reporting tung
Page 102 and 103:
Table 7. Farmers’ reported tungro
Page 104 and 105:
Table 9. Mean number (standard devi
Page 106 and 107:
than rice), so they may be reluctan
Page 108 and 109:
Community-based rice pest managemen
Page 110 and 111:
Establishment of farmers’ indigen
Page 112 and 113:
Meanwhile, insects, diseases, and n
Page 114 and 115:
Table 2. Most important diseases fo
Page 116 and 117:
Farmers’ knowledge of pest contro
Page 118 and 119:
ha -1 and above) had a lower RTD in
Page 120 and 121:
Fig. 4. Three major peaks of green
Page 122 and 123:
RBB hill -1 and 4% WSB (Fig. 6). In
Page 124 and 125:
The influence of varietal resistanc
Page 126 and 127:
Limited data exist on how resistant
Page 128 and 129:
tember plantings, reaching 13% and
Page 130 and 131:
Holt J, Chancellor TCB, Reynolds DR
Page 132 and 133:
glh4, respectively. Planting at the
Page 134 and 135:
Results and discussionMinimum unit
Page 136 and 137:
Fig. 4. Transmission efficiency of
Page 138 and 139:
Table 1. Enzyme-linked immunosorben
Page 140 and 141:
Leafhopper control by insecticides
Page 142 and 143:
Fig. 1. Cartoon used for tungro man
Page 144 and 145:
The role of vector control in rice
Page 146 and 147:
To establish relationships between
Page 148 and 149:
Fig. 1. Influence of antifeedants o
Page 150 and 151:
Fig. 4. Tungro incidence before har
Page 152 and 153:
ReferencesAryawan IGN, Widiarta IN,
Page 154 and 155:
Materials and methodsSeedbed protec
Page 156 and 157:
Table 2. Relationship of RTD incide
Page 158 and 159:
Management of rice tungro disease b
Page 160 and 161:
Results and discussionGLH populatio
Page 162 and 163:
Table 4. Field evaluation of foliar
Page 164 and 165:
3.6 to 2.7 t ha -1 . These yields w
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