Population dynamics of Nephottetix virescens in relation to tungro disease progression in pure and mixed stands of rice cultivars with different types of resistance
2001
Pedroso, J.P. (Western Mindanao State Univ., Zamboanga City (Philippines). Coll. of Agriculture) Raymundo, A.D. | Sumalde, A.C.
Populations of the green leafhopper Nephottetix virescens varied among pure and mixed stands of rice cultivars with different types of resistance in three sites during the dry and wet seasons of 1999. In most cases, the mixtures of two (IR64 and PSBRc 18), three (IR-64, PSBRc18 and IR-72), and four (IR-64, PSBRc 18, IR-72 and PSBRc 34) in closed (15 x 20 cm) and wider spacing (25 x 25 cm) and higher GLH populations. For instance, in Barangay [village] Talisayan with high disease incidence in some of these mixtures, diverse genotypes constituting these mixtures had no effect in suppressing disease development and reducing GLH populations. Population build-up was rapid in the susceptible cultivar IR-64. Pure stands of resistant cultivars also had high GLH as in IR-64. There was significant correlation between incidence and vector population in IR-64, PSBRc 34, IR-72, mixtures of two cultivars (IR-64 and PSBRc 18) and mixtures of four cultivars (IR-64, PSBRc 18, IR-72 and PSBRc 34) planted within rows. However, disease incidence in the mixtures of three, four cultivars in rows, those planted in closed (15 x 20 cm) and wide spacing (25 x 25 cm) and mixtures of four cultivars (IR-64, PSBRc 18, IR-72 and PSBRc 34) in alternate rows had no correlation with GLH population. N. virescens rapidly increased at 15 DAT and peaked at 36-43 DAT. The most critical stage was at 15 DAT when population build-up was rapid as plants were young and susceptible to infection
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