Mechanisms of competitive ability and origin of weedy rice in association with cultivated rice (Oryza sativa L.) in the Philippines

Date

6-2025

Abstract

Weedy rice (WR) can severely impact rice production through yield reduction because of its very competitive ability to reduce growth resources for cultivated rice, The biology and ecology of WR biotypes provide significant information on its origin to better understand recurrent evolution of WR biotypes and analyze its life cycle for effective weedy rice management. Genetic diversity analysis using SSR markers examined the relationships of weedy rice, cultivated rice, and wild rice varieties which point to the different origins of weedy rice biotypes with ancestries from cultivated rice and wild rice populations. From the high genetic similarity of weedy rice biotypes to wild rice populations, possible hybridization occurred between cultivated rice and wild rice. In weedy rice biotypes with high similarity to cultivated rice varıeties, the other route of origin can be the de-domestication of improved rice cultivars giving rise to weedy traits. Weedy rice has been known to generally grow faster than cultivated rice and that faster growth rate can also be due to higher rhizosphere microbial composition than cultivated rice as has been shown that root microbial abundance is related to the characteristic faster growth. More colonies of plant growth-promoting rhizobacteria (PGPR) were found in weedy rice than cultivated rice which tend to lead to nutritional competitive advantage of weedy rice in paddy soils. Majority of the PGPR isolated from WR have plant growth promoting (PGP) traits like indoleacetic acid (IAA) production, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, phosphate solubilization, and starch hydrolysis. Analysis on the early shoot and root morpho-physiological characteristics provided significant nformation onthe seedling vigor of WR. Shoot and root growths including photosynthetic parameters of WR biotypes showed early growth and development with greater tiller number, plant height, and shoot and root dry weights than cultivated rice. Nodal roots, root and lateral root lengths were significantly enhanced with higher branching and competitive indices relative to the total root length of WR. Photosynthetic parameters and percent uptake of nutrients- nitrogen (N), phosphorus (P2O5), and potassium (K2O) were significantly higher in weedy rice than cultivated rice. Weedy rice and cultivated rice compete for the same resources such as sunlight and nutrients but weedy rice has the competitive advantage of early vigor, taller plants, higher tillering ability, and high-density root system enabling better responses to growth resources than cultivated rice. And with ancestries from wild rice and de-domestication of cultivated rice, weedy rice continues to be persistent and troublesome when not managed well in rice production

Document Type

Dissertation

Degree

Doctor of Philosophy in Agronomy

College

Graduate School (GS)

Adviser/Committee Chair

Analiza Henedina M. Ramirez

Committee Member

Pompe C. Sta. Cruz, Pearl B. Sancehz, Ma. Lourdes S. Edaño, Virender Kumar

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

En – AGROVOC descriptors

ORYZA SATIVA; RICE; IRRIGATED AREA WEEDS; BIOLOGICAL WEED CONTROL; INTRASPECIFIC VARIATION; RHIZOBACTERIA; GROWTH PROMOTERS; ROOT SYSTEMS; NUTRIENT UPTAKE

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