DETERMINING GAMMA RADIATION DOSE FOR INDUCED MUTATION IN MAIZE(ZEA MAYS)

By Chilembo LeonardComp: 11004517

SUPERVISORS : DR. K. MUNYINDADR. L. TEMBO

INTRODUCTIONMaize (Zea mays L.) Maize is the most

significant cereal crop and staple food for more than 1.2 billion people in Sub-Saharan Africa (SSA) and Latin America (Vivek et al., 2005)

However, maize yield is low due to biotic and abiotic stresses on the crop

Creation of genetic variation through induced mutation from which desired mutants can be selected proves to provide great success in plant breeding programmes (Ahloowalia, 2004).

STATEMENT OF THE PROBLEM

Low maize yield is an increasing challenge in ensuring food security. This calls for breeding methods such as induced mutation to generate maize genotypes with desired traits such as drought, low soil fertility, disease and pest resistance (Parr et al., 2005).

JUSTIFICATION OF THE STUDY

Induced mutation is a significant tool for creating genetic variations among the maize genotypes (Wani and Anis, 2008).

Variations enables the selection of desired traits such as drought and low fertility tolerance to solve the problem of low maize yields (Ashraf, 2009).

OBJECTIVE

To determine the optimum gamma radiation dose for induced mutation in maize for producing desirable traits.

RESEARCH HYPOTHESIS Gamma irradiation produces mutation

derived maize lines with desirable traits (drought, high nutrient use efficiencies)

MATERIALS AND METHODSThe materials used in the study were five

genotypes: GV 635, ZARICZH 122, ZARICZH 1021, ZARICZH 131002 and ZARICZH 131008

Got from Zambia Agricultural Research Institute (ZARI) provided by the department of plant science.

MATERIALS AND METHODS CONT’D

The genotypes were irradiated at four different doses (0, 150, 300, 450 and 600 Gy)

Irradiated seeds were then planted in pots in the greenhouse

MATERIALS AND METHODS CONT’D

Planting was done on 23rd January 2016 and

The experiment was carried out for a period of 30 days.

Parameters measured

Plant germination was recorded 7 days after planting

Plant height, Leaf length, leaf width and chlorophyll content were all measured 30

days after plantingLeaf area (L × W × A ); A=0.75 (Pearce, 1975)

EXPERIMENTAL DESIGN

• Complete Randomized Design (CRD)• Two factors:– Gamma radiation dose (Gy)– maize genotypes

• 5 treatments which are gamma radiation doses (0, 150, 300, 450 and 600 Gy).

• 4 replications of radiation dose. • Data analyzed by GenSat18

RESULTS

Genotypic Mean Squares for measured Parameters evaluated across Gamma ray doses (Gy)

Source of D.f Germ Plant height Leaf length leaf Area Chlorophyll Variation MS MS MS MS MS

Genotype 4 7.534 ** 370.163 *** 144.940*** 669.3*** 59.91ns

Dose 4 9.403** 221.828 *** 180.174*** 1246.0*** 37.14ns

Genotype×Dose 16 8.851*** 139.4ns 0.11 29ns 28.638ns 42.19ns

Residual 70 2.208 3.231 6.730 106.3 25.51 CV% 16.5 4.5 4.2 16.3 15.6KEY*,**,***, Significant at P=0.1, P=0.05 & P=0.001 respectively , ns=Non significant, MS=Mean Square, DF=Degree of Freedom.

Fig 1: Effects of gamma radiation dose on plant height

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GV 635 ZARICZH 1021 ZARICZH 122 ZARICZH 131002 ZARICZH 131008

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GENOTYPE AND RADIATION DOSE

Plan

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Fig 2: % Reduction in plant height

150 Gy 300 Gy 450 Gy 600 Gy0

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Gamma radiation dose

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Fig 3: Effects of gamma radiation dose on leaf length

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GV 635 ZARICZH 1021 ZARICZH 122 ZARICZH 131002

ZARICZH 131008

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GENOTYPE AND RADIATION DOSE

Leaf

leng

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m

Fig 4: % Reduction in leaf length

150 Gy 300 Gy 450 Gy 600 Gy05

101520253035

% Reduction

Gamma radiation dose

Leaf

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Fig 5: Effects of gamma radiation dose on leaf area0

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GENOTYPE AND RADIATION DOSE

leaf

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Fig 6: % Reduction in leaf area

150 Gy 300 Gy 450 Gy 600 Gy0

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DISCUSSIONAt 0 Gy all the genotypes showed normal growth

but had some stimulating growth at 150 GyThis is because the stimulatory effect is attributed

to the production of growth hormone, kinetin, which forms hormonal balance

Hormonal balance is formed due to increasing number of cells to overcome stress factors such as frequency of chromosomal damage with increasing fluctuations of light intensity and temperature because of gamma radiation (Chung and J.S. Kim, 2007).

CONCLUSION

The optimum gamma radiation dose found for irradiating maize genotypes was 450 Gy

This is because radiation dose of 450 Gy caused a percentage reduction growth in the parameters measured of more than 20%

A dose causing percentage reduction of 20 and above is considered optimum, where maximum mutation is produced with minimal damage to the plant (Kangarasu S, 2014).

RECOMENDATION

Since the optimal gamma irradiation dose was determined, growing maize plants irradiated at 450 Gy to maturity to observe yield and other characteristics should be done.

References• Ahloowalia (2004). Global impact of mutation-derived varieties. Euphytica 135:187-204.

• Ashraf M (2009). Changes in antioxidant enzymes and some key metabolites in some genetically diverse cultivars of radish (Raphanus sativus L.). Environ. Exp. Bot., 67: 395-402

• Chung and J.S. Kim, 2007. Effects of markers. African Journal of Biotechnology, gamma irradiation on morphological changes and 8(19): 4824-4829. biological responses in plants. Micron, 38: 553-564

• Kangarasu S (2014). Determination of Lethal Dose for Gamma Rays and Ethyl Methane Sulphonate Induced Mutagenesis In Cassava (Manihot Esculenta Crantz). Department of Plant Genetic Resources, Centre for Plant Breeding and Genetics, Tamil Nadua Agricultural University, Coimbatore.

• Parry et al., (2007). Prospects for increasing photosynthesis by overcoming the limitations of Rubisco. Journal of Agricultural Science 145, 31–43.

• Pearce et al., (1975). Maize plant physiology. Iowa State University Press, Ames, IA. USA

• Vivek et al., (2005). Characterization of maize germplasm grown in eastern and southern Africa: Results of the 2004 regional trials coordinated by CIMMYT. Harare, Zimbabwe. CIMMYT. 68pp.

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