K.G.Dinuki Ishara SiriwardanaDr. Shyama R Weerakoon

Dr.S.SomarathneDepartment Botany, The Open University of Sri Lanka

WEEDY RICE(Oryza sativa f. spontanea)

BACKGROUND

WEEDY RICE - (Oryza sativa f. spontanea )

Definition

Broadly and genetically, conspecific with Oryza sativa that competes

cultivated rice and other crops

Belongs to the Family Poaceae

It commonly causes yield reduction and affects the quality of rice

grains

Weedy rice could occur due to several factors like

1. Gene flow between wild and cultivated types

2. Old rice varieties becoming fereal

3. Crosses between cultivated rice and wild rice

Highly variable and appears to be an intermediate between wild &

cultivated rice

Long-term sympatric distribution has led to similarities between

weedy and cultivated rice

Selective herbicides cannot be used to control weedy rice

Origin of weedy rice in Asia is as yet unclear

Thought that they are natural hybrids of cultivated (O.sativa) and

wild rice species (O.rufipogon and O.nivara)

Strongly characterized by its seed shattering and dormancy, which

increase the distribution of this species

MORPHOLOGICAL CHARACTERS OF WEEDY RICE

Shows a wide variability in anatomical, biological and physiological

features, which differ from cultivated rice

But they are very similar to cultivated rice in the vegetative stage

Weedy rice are generally

more heavily tiller

more open or spreading

have weaker culms

produce more straw

germinate and emerge a day or two earlier

emerge from greater depths

Weedy rice are generally taller

weedy rice is variable in awn length

Exhibit more rapid seedling growth when compared to the cultivated rice that they infest

Internodes color after flowering may be purple, purple lines, green, light gold

Weedy rice shatters easily

A

WHAT PROBLEMS DOES WEEDY RICE CAUSE TO THE

RICE CULTIVATION

Weedy rice competes with cultivated rice and reduces crop yield

Farmers cannot have harvest the grain of weedy rice as it tends to

mature earlier and to shatter readily

Therefore it increases the costs of production, reduces yield, lowers

the market value of their rice crop

If not controlled properly can infested crop land unfit for rice

production

Weedy rice was reported first in the Eastern province of Sri Lanka in early

1990s, has now spread into many rice growing areas

Weedy rice affects both quantity and quality of national rice production

Therefore, its beneficial to focus a research to assess the level of

morphological diversity of weedy rice population found in districts where

weedy rice problem is considerably high

Detailed study of vegetative and reproductive development of weedy rice

biotypes can give us the ability to identify weedy rice biotypes at their

different growth stages

This will also lead us to know the biology of weedy rice such as life table,

growth pattern and life cycle

Weedy rice highly infected areas in Sri Lanka

1. Matara

2. Hambantota

3. Ampara

4. Kandy

5. Matale

6. Kurunegala

7. Polonnaruwa

8. Anuradhapura

9. Batticalo

10. Puttalam

11. Mannar

12. Jaffna

13. Colombo

OBJECTIVE OF THE STUDY WAS TO

Study the agro-morphological variation among different weedy

rice accessions collected from rice growing areas in Matara

District and differentiation of them

MATERIALS AND METHOD

Weedy rice infested paddy field in Matara district

Weedy rice infested paddy field in Matara district

District Season Location GPS values

Matara Yala2012 Akurugoda 06°03'N,80°33'E

Matara Yala2012 Hakmana 06°08'N,80°65'E

Matara Yala2012 Mapalana 07°15'N,80°01'E

Matara Yala2012 Morawaka 06°14'N,08°36'E

Matara Yala2012 Weligama 05°59'N,80°26'E

Table 1 - Season, Location and GPS values of Matara District which we collected Weedy Rice and Cultivated Rice

Weedy rice and cultivated rice sample collected in Matara district

Identification and labeled of weedy rice biotypes

Germination of Weedy rice and cultivated rice biotypes

Young seedlings of weedy rice biotypes and cultivated rice

Seedlings were transplanted to plastic pots

Complete Randomized Design (CRD) for Matara district

plant house, which the experiment conducted at OUSL, Nawala

Data CollectionTable 2- The Agro-morphological characters with were measured from Seedling

stage to Seed maturity stage (based on PGRC Catalogue, 1999)

Plant Height (cm) Ligule Length (cm)

Leaf Blade Length(cm) Ligule Color

Leaf Blade Width (cm) Ligule Shape

Leaf Blade Pubescence Collar Color

Leaf Blade Color Auricle Color

Basal Leaf Sheath Color Days to Heading

Leaf Angle Culm Length (cm)

Flag Leaf Angle Culm number

Culm Angle Panicle threshability

Culm Diameter (cm) Awing after full heading

Internode Color Awn Color

Culm Strength Apiculus color

Panicle Length (cm) Stigma color

Panicle Type Lemma and Palea color

Secondary Branching Lemma and Palea pubescence

Panicle Exsertion Sterile Lemma color

Panicle axis Sterile Lemma length

Panicle shattering Spikelet Sterility

100 Grain Weight Endosperm type

Grain Length Scent

Grain Width Leaf Senescence

Seed Coat Color Maturity

These data were analyzed by using SASS software package

Character Sumof Squares

df Mean Square F Sig.

PH cm –Plant height (cm) 48042.943 21 2287.759 7.865 .000

LBL cm- Leaf blade length (cm) 3844639.212 21 183078.058 .867 .633

LBW cm- Leaf blade width (cm) 7.054 21 .336 5.694 .000

DoH- Days of heading 2358.186 21 112.295 1.902 .016

CuL cm-Culm length (cm) 17980.746 21 856.226 5.180 .000

CuD cm- Culm diameter (cm) at flowering period

3006.646 21 143.174 3.138 .000

PaL cm- Panicle length (cm) 981.233 21 46.725 8.306 .000

GWg -100 Grain weight at maturity (g) 3.854 21 .184 1.330 .175

GLcm- Grain length (cm) 1.458 21 .069 21.687 .000

GWcm-Grain width (cm) .206 21 .010 3.133 .000

Matu- Maturity 2796.792 21 133.181 3.264 .000

Table 3- The Agro-morphological characters which differ at P≤0.05 are included

According to the Cluster Analysis,

2 main group-A and B

Group A- 3 sub group (3 rice cultivars)

Group B- 3 sub group (3 weedy rice bio-types)

Indicating the presences of 3 weedy rice bio-types

According to the Classification and Regression Tree Analysis,

4 agro-morphological characters were important

Dendrogram of hierarchical clustering using dissimilarity values from morphological Characteristics of observed WR accession and rice cultivars

Classification and Regression Tree Analysis

CONCLUSIONS

Four out of forty seven have identified as top key characters

Spikelet Sterility at maturity, Leaf Blade Length, Ligule Shape,

Ligule Color

Three different bio-types were identified in Matara District

The higher diversity among WR accessions in Matara District indicates

that there would be a higher possibility of out-crossing rate between

cultivated rice varieties and their weedy relatives which could lead to

establish WR as a prominent weed

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ACKNOWLEDGEMENT

I acknowledge the guidance given by Dr. Shyama R. Weerakoon

and Dr. S. Somaratne in carrying out this research project and

providing facilities to conduct this research at the Department of

Botany, Faculty of Natural Science, Open University of Sri Lanka

THANK YOU