Agromorphological characteristics and tungro response of selected Philippine traditional rice varieties.

Abstract

Traditional rice varieties (TRVs) are affected by rice tungro disease, which is one of the constraints of rice production. Planting of TRVs must consider varieties that possess both tungro resistance and good agromorphological traits. This study aimed to identify tungro resistant Philippine TRVs with good agromorphological traits. Data on agromorphological traits and tungro response of 61 TRVs were obtained with permission from the PhilRice Genebank. Varieties with tungro resistance and good agromorphological characteristics including qualitative and quantitative traits were determined. Among the 61 TRVs presented in this study, six have intermediate resistance while 55 are susceptible. Tungro intermediate resistant varieties with good agromorphological traits are: Dinurado (Ilocos Norte) with intermediate culm lodging resistance (CLR), semi-compact panicle branching attitude (PBA) and low panicle shatterring (PS); Denorado 1 (Maguindanao) with semicompact PBA; Azucena 4 (Negros Occidental) with strong CLR, slightly drooping panicle main axis attitude (PMA) and low PS; Azucena 1 (North Cotabato) with semi-compact PBA and moderate PS; Maliket (Ilocos Norte) with intermediate CLR, strong upright PMA, semi-compact PBA and very low PS; and Milagrosa Pula (Palawan) with strong CLR, and semi-compact PBA. Spearman's rank correlation analysis using 12 agromorphological traits of 61 TRVs showed that none of the four qualitative and eight quantitative traits has significant correlation with tungro response. Screenhouse evaluation showed that all 15 Maguindanao TRVs tested in this study were tungro susceptible with disease index (DI = 9) comparable to the susceptible control variety, TN1. Varieties with susceptible response have high disease incidence, high symptom severity rating and high area under disease progress curve (AUDPC). Most of the Maguindanao TRVs have intermediate CLR, semi-upright PMA and semi-compact PBA. Some of the Maguindanao TRVs possessing good agromorphological traits are Dinorado 2 with desirable plant height, strong CLR, semi-upright PMA, semi-compact PBA and moderate PS. Kua-Kua has desirable panicle length (PL) (30.6 cm) with intermediate CLR, semi-upright PMA and semi-compact PBA. Inabaka has desirable panicle length (PL) (35.4 cm), semi upright PMA and semi compact PBA.