Weed Science (2006) 54, 1122-1131

Fernando B. Pérez de Vida, Emilio A. Laca, David J. Mackill, Grisel M. Fernández and Albert J. Fischer (2006)
Relating rice traits to weed competitiveness and yield: a path analysis
Weed Science 54 (6), 1122-1131
Abstract: Resistance to herbicides in the most important weeds threatens the sustainability of California rice. Weed-competitive rice cultivars could be a low-cost and safe nonchemical addition to an integrated weed management program. Trade-offs between competitiveness and productivity and inconsistent trait expression under weedy and weed-free conditions could complicate the breeding of competitive rice cultivars. A 2-year competition experiment was conducted in the greenhouse involving eight rice cultivars and two weed competition regimes (presence or absence of late watergrass) to examine the effects of rice weed-suppressive ability and tolerance to weed competition (weed tolerance) on rice yield. Competition reduced average rice yield from 32 to 48%, and watergrass biomass from 44 to 77%. Path analysis suggested that enhancing rice weed-suppressive ability and weed tolerance while minimizing possible productivity trade-offs should promote early (12 d after seeding) growth and light-capture traits followed by moderate growth rates before heading and a vigorous grain filling period. Crop growth rate (CGR) after heading was a relevant determinant of yield (direct path: 0.82, P < 0.01) and correlated (r = 0.30, P < 0.01) with weed tolerance. Late biomass accumulation was negatively correlated with harvest index and CGR during ripening (r = -0.46, P < 0.01); thus, late-season competitiveness can lower productivity. Rice traits conferring competitiveness were correlated across weed competition regimes (r = 0.36-0.81, P < 0.01). However, significant cultivar-by-competition and cultivar-by-year interactions suggest that selection efficiency would be greater when traits are identified under competition and in different environments. This study relates to the phenotypic expression of traits for competitiveness. Breeding competitive cultivars will require additional knowledge on trait heritability, genetic correlations with competitiveness, and on the effects of the environment upon gene expression.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Albert J. Fischer

Research topic(s) for pests/diseases/weeds:
damage/losses/economics
resistance/tolerance/defence of host

---

Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Echinochloa phyllopogon (weed)	Rice (Oryza)	U.S.A. (SW)