Role of water management and seed treatments on the growth of rice and weeds

Swarna Herath

Date

3-2015

Abstract

Flooding following direct seeding reduces germination and growth in rice and helps control weeds. However, crop establishment under flooding conditions can be enhanced through proper rice seed handling practices combine with tolerant rice genotypes. Physiological and biochemical mechanisms of rice and weed associated with flooding during germination have not been well evaluated. This study aimed to understand the physiological and biochemical response of rice, weedy rice (Oryza sativa (L)f. Spontanea), Echinochloa spp and seed priming and prior seed storage treatments to flooding during germination. Philippines Weedy Rice (PWR), Vietnam (VWR) and cultivated rice genotypes: IR64, IR42, Khao Hlan On (KHO), Mazhan Red (MR) and Khaiyan and two Echinochloa spp: Echinochloa crus-galli (ECR), Echinochloa colona (ECOL), were included in this study.

KHO and MR had better seedling emergence, faster shoot and root elongation and higher biomass production at 5 and 10 cm flooding. Lower Malondialdehyde MDA) content, higher total phenolic content (TPC), higher superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase oX) and higher amylases activities of KHO and MR were associated with tolerance to flooding during germination. Echinochloa species had high MDA, low TPC, lower SOD, CAT, APX and POX activity and lower amylase activity. Weedy rice had low seedling emergence, poor shoot and root growth and reduced biomass production under flooding. However, it had the lowest lipid peroxidation, highest TPC, high SOD, CAT, APX and POX activity and lower amylase activity.

Seed priming improved the germination, growth, seedling vigor, survival, carbohydrate metabolism and reduces lipid peroxidation under flooding. Lower MDA content, high soluble sugars and amylase activity of primed treatments were associated with their high growth and seedling survival under flooding. Priming improved the physiological traits associated with flooding tolerance more on IR64 and further improved tolerant ability of KHO under flooding.

Newly harvested KHO and Khaiyan had lower MDA and high TPC, dry seeds before Sowing and higher germination, seedling vigor, survival, and higher amylase activity under flooding conditions. Increasing seed age and ambient storage condition negatively affects the seedling survival and amylase activity. Response of KHO and Khaiyan are more pronouns to seed age and flooding compared to IR64 and IR42.

Induction of SOD, CAT, APX, POX activities, amylases and TPC provide the tolerance ability of rice genotypes to flooding during germination. Reduced growth, amylases and lower activation of antioxidants of Echinochloa spp confirms the susceptibility to flooding during germination. Higher activation of SOD, CAT, APX, POX, TPC and lower amylase activity of weedy rice provides higher protective mechanisms to alleviate the flooding stress. Combining tolerant rice genotypes with pre- seed handling practices are important to achieve improved crop establishment, especially areas prone to early flooding and to ensure proper weed management in direct-seeded rice.

Document Type

Dissertation

Degree

Doctor of Philosophy in Agronomy

College

Graduate School (GS)

Adviser/Committee Chair

Aurora M. Baltazar

Committee Member

Pompe C. Sta. Cruz, Pearl B. Sanchez, Abdelbagi M. Ismail, David E. Johnson

Call Number

LG 996 2015 A42 H47

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