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African Crop Science Journal
African Crop Science Society
ISSN: 1021-9730 EISSN: 2072-6589
Vol. 8, Num. 4, 2000, pp. 441-445
African Crop Science Journal, Vol. 8. No. 4, pp. 441-445

African Crop Science Journal, Vol. 8. No. 4, pp. 441-445

SHORT COMMUNICATION

ASSESSMENT OF THREE SUBSTRATA FOR MAIZE SEED TESTING

S.A. AJAYI, M.A.B. FAKOREDE and B.A. OWOLABI
Department of Plant Science, Obafemi Awolowo University, Ile-Ife, Nigeria

(Received 9 November, 1998; accepted 10 June, 2000)

Code Number: cs00047

INTRODUCTION

Seed is the key element in setting up, diversifying and improving agricultural production. Whether a crop will perform well or not depends on the quality of the seed planted. Seed quality is of international agronomic concern and the recent upsurge of interest in seed quality has accentuated the awareness regarding its importance in crop production. With the adoption of modern agricultural techniques, growers require high quality seed that is capable of rapid and uniform emergence under a wide range of environmental conditions. High quality seed is the basis of higher agricultural productivity. The upsurge of interest in seed quality has brought seed testing to the limelight as an integral part of quality control and assurance in all seed programmes.

Seed testing emerged as a means of providing growers with a measure of true sowing value in order to protect them from purchasing poor quality seed. The first seed testing station, established by Nobble in Germany about 1876, laid the principles for seed testing and by the beginning of the 20th century many seed stations were established in Europe and North America. As the seed trade developed between countries, seed testing played an important role in guaranteeing good quality seed to the farmer (Gassim, 1988).

Among substrata that can be used for seed testing are paper towel, kimpack, blotter paper, filter paper, cotton wool, sawdust, and soil (Muliokela and Kaliangile, 1995; Louwaars and Marrewijk, 1996). Paper towels and sand are the most commonly used for testing seed of grain crops like maize. Skinner and Schroeder (1978) reported that in soybean rolled towels gave more uniform results than sand.

Only paper towels and sand are acceptable by International Seed Testing Association (ISTA) for testing maize seeds (ISTA, 1987). But, paper towel is not readily available and often too costly to seed programmes of many developing countries (Louwaars and Marrewijk, 1996). Besides, its use requires technical skill and experience. Thus, it is imperative to find cheaper, readily available and easy-to-use substrata that are comparable to internationally acceptable standards and give uniform results. Substrata providing moisture for germination in seed testing must be easy to handle and use, cheap, non-toxic, free from pathogens and, if it is to be re-used, must be easily sterilised (Challam et al., 1967; Muliokela and Kaliangile, 1995; Louwaars and Marrewijk, 1996). Soil microbiologists suggest that substrata for assessing vigour status and subsequent field performance or true sowing value of a seed lot should not be sterilised so as to approximate real field conditions as much as possible.

The objective of this study was to make a comparative assessment of three substrata-sand, soil and sawdust, each sterilised and unsterilised for testing maize seed germinability.

MATERIALS AND METHODS

High quality seed of white maize hybrid, Oba Supa 1 were used for the study. The seeds had been stored in a deep freezer for about four months before this study was carried out. Riverbed sand, topsoil and sawdust were used as substrata. Sand and soil were sieved with a 2 mm sieve to ensure uniform particle size. For each of the substrata a part was sterilised and another kept unsterilised. The three substrata were separately mixed with water up to about 60% water holding capacity. Three plastic containers (replications) were filled with moistened substratum. One hundred seeds were evenly-spaced on the substratum per replication and were covered with the substratum up to about 2 cm level. The first germination count was made on day 5 and final count on day 7 after planting. The values were substituted into the following formula (Fakorede and Agbana, 1983) to obtain emergence index (EI).

EI = S No. of seedlings emerged in days x 100)

No. of seedlings emerged by day 7 after planting

Additionally, data were collected on number of primary roots (RNO), length of the longest root (RLT), and shoot length (SLT). This was done 7 days after planting using 50 seedlings per replication. The experiment was repeated four times but germination and emergence index data were collected only thrice. Analysis of variance was performed on the pooled data collected and where "F" statistics indicated significance, means were compared using LSD at P=0.05.

RESULTS

Sterilisation of substrata had no effect on all the traits except shoot length. Significant substrata x sterilisation and experiment x substrata x sterilisation effects were also observed for the seedling traits (Table 1). Despite the non-significant substrata mean squares for germination percentage, comparison of means across replications, experiments and sterilisation showed that germination on sand was higher than on soil and significantly higher than on sawdust and so was the length of primary roots of the seedlings (Table 2). Shoot length of seedlings grown on sterilised substrata were significantly longer than on unsterilised ones (Fig. 1). The contributions of unaccountable sources of variation (error) to the total sum of squares for germination percentage and emergence index were much higher than the known sources (Table 3). Substrata made proportionately higher and appreciable contributions to the total sum of squares for the seedling traits. Sterilisation contributed less than 4% to the total sum of squares for all traits measured.

Table 1. Mean squares from the combined analysis of variance for all traits measured
Source df Germination % Emergence index (days) No. of Roots Root length (cm) Shoot length (cm)
Rep (expt) 8(6)1 1.05 0.01 0.04 0.74 2.17
Experiment 3(2) 24.01 0.01 1.11** 36.74** 18.45**
Substrata 2 41.17 0.12 0.21** 566.89** 74.76**
Sterilization 1 7.04 0.10 0.13 0.003 16.39**
Subt x Ster 2 30.50 0.0002 0.15* 3.70* 5.05*
Expt. x Subt 6(4) 44.31* 0.02* 1.25** 21.45** 7.59
Expt x Ster 3(2) 24.01 0.01 0.09 19.88** 3.06
Expt x Subt x Ster 6(4) 26.47 0.01 0.12 16.43** 17.40**
Error 40(30) 12.91 0.006 0.04 1.03 1.21
C.V.   3.73 1.50 4.05 7.29 10.99
Model R2(%)   58.04 61.97 88.08 97.40 89.41
df for germination percentage and emergence index*, ** indicate significant at P = 0.05 and 0.01 levels of probability, respectively

Table 2. Comparison of means for germination and other seedling traits
Factor   Germination (%) Emergence index (days) No. of roots Root length (cm) Shoot length (cm)
Sterilisation Unsterilised 96.72a 5.17a 5.23a 13.93a 9.53a
Sterilised 96.00a 5.14a 5.15a 13.92a 10.48b
Substrata Soil 96.97ab 5.18a 5.18ab 14.51a 10.28a
Sand 97.47a 5.13a 5.28a 18.46b 11.62b
Sawdust 94.64b 5.17a 5.10b 8.80c 8.12c
Means with different letters within the column of the same factor are significantly different at P = 0.05

Table 3. Percentage of the total sums of squares attributable to each source of variation for germination and seedling traits
Source of variation Germination % Emergence index (days) No. of roots Root length (cm) Shoot length (cm)
Rep (Expt) 0.68 17.69 2.43 0.37 3.80
Expt 5.20 4.01 22.49 6.95 12.14
Substrata 8.92 3.20 2.79 71.52 32.78
Sterilisation 0.76 2.83 0.85 0.0002 3.59
Subt x Ster 6.61 0.04 2.04 0.50 2.21
Expt x Subt 19.20 3.85 50.60 8.12 9.98
Expt x Ster 5.20 2.71 1.83 3.76 2.01
Expt x Subt x Ster 11.47 2.54 5.06 6.22 22.89
Error 41.96 38.03 11.92 2.60 10.59

Discussion

Germination percentage obtained on soil was comparable to those obtained on sand and on saw dust but sand gave higher percentage than sawdust though the differences were low, they can be misleading if equally highly vigorous germinating lots with significant vigour differences are being tested. The substrata were distinctly different in supporting seedling growth, especially of root and shoot growth with sand performing better than the other two. When seed testing is done with the sole objective of assessing germination capacity, soil may be used in the absence of sand but when testing involves seedling evaluation only sand will permit protrusion and/or expression of the traits of interest better. Sterilised substrata supported better seedling growth than germination. The difference in the mean values obtained on sterilised and unsterilised substrata were too insignificant as to make sterilisation a must for substrata to be used for seed testing. But, beside the possibility of build-up of microbial population and other growth-retarding/toxic substances from repeated usage, the significantly higher shoot length obtained on sterilised over unsterilised substrata is strong enough evidence to support sterilisation of substrata to be used for testing maize seeds. If the shoots of the seedlings are not long enough to penetrate the substratum, it will not be possible to make germination count. Strilised sand permitted protrusion of the relevant organs out of the substratum than any other substrata. Much of the significant experiment x substrata and experiment x substrata x sterilisation effects resulted primarily from the first experiment compared to the other three experiments. When experiment 1 was excluded from the analysis, non-significant mean squares due to these interaction effects involving experiment were detected. Sand sterilised and unsterilised, followed by sawdust, gave more uniform test results than soil at all the experiments.

The proportionately higher contribution of unaccountable sources of variation (lumped together as error) to the total sums of squares for germination and emergence index and the magnitudes of the R2 obtained for these traits indicate that many other extraneous factors (for example light, humidity/moisture and temperature conditions) need to be considered in seed testing. The recommendation that seed testing should be done under controlled conditions (temperature, light, humidity, etc.) could also be explained against this background. Similarly, the magnitude of the contributions of the known sources of variation to the total sum of squares for seedling traits indicate that the choice of substrata should receive a higher priority when seed testing involves seedling evaluation. A combination of suitable substratum that will permit satisfactory expression of relevant seedling traits and a high degree of control of atmospheric condition to a level with minimal fluctuation is required for seed testing. Of the three substrata used in this study, sterilised sand followed by unsterilised gave the best results. Under the conditions of this study, seedling growth on sawdust was unsatisfactory compared to what was obtained from other substrata. Its use will not permit optimal expression of the inherent qualities of maize seed lots leading to false conclusions as to the vigour of the seed lot.

REFERENCES

  1. Challam, G.V., Singh, A. and Doublas, J.E. 1967. Seed Testing Manual. Indian Council of Agricultural Research and USAID, New Delhi.
  2. Fakorede, M.A.B. and Agabana, S.B. 1983. Heterotic effects and association of seedling vigour with mature plant characteristics and grain yield in some tropical maize cultivars. Maydica 27:327- 338.
  3. Gassim, A.B. 1988. Seed quality and vigour. In: Quality Seed Production. van Gastel, A.J.G. and Kerley, J. (Eds.), pp. 15 - 32. ICARDA, Syria.
  4. International Seed Testing Association (ISTA). 1987. Handbook of Vigour Test Methods. International Seed Testing Association, Zurich, Switzerland.
  5. International Seed Testing Association (ISTA) 1993. International rules for seed testing. Seed Science and Technology 21: (Supplement).
  6. Louwaars, N.P. and Marrewijk, G.A.M. 1996. Seed Supply Systems in Developing Countries. CTA-WAU, The Netherlands.
  7. Muliokela, S.W. and Kaliangile I. 1995. Seed quality control. In: Zambia Seed Technology Handbook. Muliokela, S.W. (Ed.), pp. 106-146. Ministry of Agriculture, Food and Fisheries, Zambia.
  8. Skinner, J.L. and Schroeder ,E. M. 1978. Comparison of paper towel and sand as substrata for soybean seeds. Seed Science and Technology 6:225-231.

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