Publications

Dr K.A. Mettananda

1. Use of photoperiod in identifying suitable cultivars of big onion (Allium cepa l.) for cultivation in the dry zone of Sri Lanka. Tropical Agriculturist, DOA, 2001(Accepted).
2. Effect of environmental factors on shelf life of b'onion. Tropical Agriculturist, DOA, 2001(Accepted).
3. Effect of storage environment, packing material and seed moisture content on storability of maize (Zea mays l.) Seeds. Annals of the Department of Agriculture, 2001, 3 131-142.
4. Effect of pre-harvest grain discoloration on seed quality of rice (Oryza sativa L.). Proceedings of the Annual Symposium of the Department of Agriculture, Sri Lanka., 21-22 September, 2000., Plant Genetic Resources Centre, Gannaoruwa, Peradeniya. Pp. 189 - 198.
5. The effects of plant size and leaf number on the bulbing of tropical short day onion cultivars (Allium cepa L.) under controlled environments in the United Kingdom and tropical field conditions in Sri Lanka.., Journal of Horticultural Science and Biotechnology, UK. 74 (5) 622 - 631.
6. The effects of 12 and 16 hour daylight treatments on the onset of bulbing in 21 Cultivars of onion ( Allium cepa L. and its implication to screening germplams for use in tropics., Journal of Horticultural Science, UK.2 983 - 8.
7. Control and Manipulation of Bulbing in Onion under Tropical Conditions. PhD. theses, Wye College, University of London
8. On Station and on farm Research Proc. Weed Science Workshop. Department of Agriculture, Peradeniya, Sri Lanka. May 7-8, Pp69-74
9. Effect of Planting method and Earthling-up at flowering on the Pod Yield of Erect type ground nut., Proc. Sri Lanka Ass. Advmt. Sci. 45 (1)
10. Effect of the condition of seedlings at transplanting on the growth and yield of large onions., Proc., Sri Lanka Ass. Advmt. Sci 46 (1)
11. The Effect of residue management and tillage on flower and pod abortion, water use efficiency, and Soybean Yield., food Legumes-Coarse Grain Newsletter, No. 06 (FLDBEN).
12. Guidance to maximize profit from soybean cultivation., Soynews, vol .5, Oct. 1982.

2. Effect of environmental factors on shelf life of b'onion
K.A. Mettananda & E.R.S.P. Edirimanna Field crops Research and Development Institute, Maha Illuppallama.

Abstract
An experiment was conducted to identify the effect of environmental temperature and relative humidity on the shelf life of b'onion. Different geographical locations were used for the experiment in order to test the storability under different temperature (T o) and relative humidity (Rh) conditions. Results reveled that the shelf life of onion in low temperature locations such as Sita Eliya, Rahangala, and Bandarawela where averaged minimum temperature is less than 15 oC are comparatively lower than that of Maha Illuppallama and Homagama where average minimum temperature is between 23 - 28 oC. Level of relative humidity recorded in any of the locations used (60 - 90%) have not been favourable in reducing sprouting losses effectively but spraying of sprouting inhibitor before maturity has helped to reduce losses due to sprouting up to 65%. However, the comparative advantage of using sprouting inhibitor was low in low temperature location where average minimum temperature was below 15 oC. Over all results indicated that average minimum temperature and relative humidity conditions at low country location such as Homagama and Maha Illuppallama ( T o - 23 - 28 oC and Rh - <80%) are more suitable than those of mid and up country locations tested for long term storage of b'onion.

3. Effect of storage environment, packing material and seed moisture content on storability of maize (Zea mays l.) Seeds
K.A.. Mettananda, S.L. Weerasena and Y. Liyanage Seed Certification and Plant Protection Centre, Peradeniya

Abstract
Most seed lots fail to germinate when stored for about 5 - 6 months in woven polypropylene sacks (poly-sacks) at 12% moisture level, which is the method used in Sri Lanka to store maize seeds. This has become a constrain to increasing the crop extent. Therefore, it is necessary to find alternate methods to store maize seeds for a longer period without losing viability below the required minimum. Well-dried maize seeds were packed in poly-sack, clear and white polythene bags. Two moisture levels were used viz: 8% and 12%. Thes were stored in four environments; at Rahangala, Kundasale, and Peradeniya under ambient conditions and in a cold room at the vegetable seed centre, Gannoruwa. Standard germination and field germination were tested every 30days after starting the experiment. Germination of maize seeds stored in poly-sacks under room temperature in Peradeniya, Kundasale and Rahangala had viability below acceptable levels after 6 months, 8 months, and 10 months respectively. Longest storability was recorded in cold room with all packaging used and at both moisture levels. Seeds stored at Rahangala ranked 2nd in storability. Storage in poly-sacks was good only under cold room conditions. Seeds stored in polythene at both 12% and 8% moisture levels were superior in storability compared to those stored in poly-sacks in maintaining the germination level in all the environments tested. Effect of low seed moisture was prominent only towards the declining phase of seed germinability in different treatments, which were after12 months.

4. Effects of pre-harvest grain discolouration on seed quality of rice (Oryza sativa L.)
K.A. Mettananda, S.L. Weerasena and K.H.T.M. Perera, Seed Certification and Plant Protection Centre, Peradeniya.

Abstract
Discolouration lowers the quality of both paddy (Oryza sativa L.) seed and consumption grain. Panicle submergence with lodging is the major reason for seed discolouration. Presently, seed lots with up to 25%-discoloured seed are accepted as seed paddy if they meet other seed quality standards. However, effects of different levels of seed discolouration on seed quality have not being previously evaluated. A study was undertaken at the Seed Testing Laboratory, Peradeniya to quantify the effects of four discolouration levels; 0-5%, 20-25%, 45-50%, and 75-80% of two varieties; Bg 300 and Bg 94-1 on seed viability, germination and seedling vigour. Results indicate that all samples including the 0-5% discolouration level were infected with Fusarium, Helminthosporium, and Pyricularia spp. Samples with up to 50% discolouration had acceptable levels of viability and germination at the beginning. However, during storage seed lots with 0%, 25%, and 50% discolouration levels of both varieties declined in viability to below 85% by 3 months, 2 months, and 1 month, respectively. Seedling growth rate was lower in all lots from the beginning when compared to unaffected lots and declined gradually with storage. Level of seed discolouration increased by about 25% in all the lots including 0-5% lot within 3 months of storage, perhaps through contamination. Therefore, rice seed discoloured due to submergence during maturation, including lots with very slight discolouration cannot be recommended as seed rice, especially when it is required to store them for more than 3 months before sowing.

5. The effects of plant size and leaf number on the bulbing of tropical short day onion cultivars (Allium cepa L.) under controlled environments in the United Kingdom and tropical field conditions in Sri Lanka.
K.A Mettananda and R. Fordham Wye College, University of London, Ashford, Kent TN25 5AH, UK

Summary
Experiments were conducted in controlled environment condition in the UK and under tropical field conditions in Sri Lanka to determine the effects of plant size in similarly aged onion seedlings at transplanting on their subsequent growth and development. Results indicated that the size at transplanting, in terms of leaf number, leaf area and total weight, continues to affect to the size of the plant until maturity. Under low light conditions (maximum PAR levels of 800 µ mol m -2 S -1) and low night temperatures (minimum 11 0 C ) in the UK, transplant size was negatively correlated with time to onset of bulbing and maturity, and positively correlated with bulb weight, bulb weight, and percentage contribution high night temperatures (> 20 0 C ) in Sri Lanka, transplant size was positively correlated with time to onset of bulding and maturity, percentage of thick neck bulbs, and yield of good quality bulbs. It was negatively correlated to percentage bulbbing and percentage contribution from scale leaves to total bulb weight. In practice it should, therefore, be possible to manipulate plant size during the nursery stage to optimize the timing of bulb production and final bulb. size: under favorable conditions of light and temperature small transplants should bulb earlier and produce high quality bulbs whereas larger transplants may produce later and larger bulbs but with increased proportion of thick necks. Contrasting finding under low light and temperature relative to high light and temperature conditions are discussed in terms of a postulated requirement for carbohydrate and a critical concentration of a building stimulus.

6. The effects of 12 and hour day-length treatments on the onset of bulbing in 21 onion cultivars (Allium cepa L ) and its application to screening germplasm for use in the tropics
K.A Mettananda and R. Fordham Wye College, University of London, Ashford, Kent TN25 5AH, UK

Summary
Bulbing in onion is primarily controlled by photoperiod and is promoted by long - day conditions. Cultivars differ in their sensitivities to increasing photoperids and cultivation of onion in tropical regions is dependent on identifying accessions capable of bulbing under the relatively short prevailing daylenths. The bulbbing behavior of 21 onion cultivars was therefore studied under short (12 and long (16) photoperiods in controlled environments in the UK and under field conditions in Sri Lanka with the objectively of developing simple and rapidscreening techniques for identifying cultivars for tropical regions. There was a high correlation between the time taken for bulding of individual cultivars under 16 and 12h photoperiods in both environments as indicated by a bulbing ratio of 2.0 bulb scale initiation, and bulb maturity. The sequence in which the cultivars bulbed remained constant under the two photoperiods but the time taken was reduce by between 50-70% under the long 16h day condition. There was also a high correlation between the time taken to achieve a bulbing ratio of 2.0 (Which can be determined non destructively) under an extended 16h photoperiod, the time to bulb maturity under tropical field conditions where the prevailing daylenth was approximately 12 h. These findings are discussed in terms of their application to screening of onion germplasm and cultivars for use in different regions. the CVS early Lockyer Brown Superex and Agrifound Rose were very early maturing followed by an " intermediate" group consisting of CVS Galil, H489, Agrifound Light Red , Red Creole C5 and H - 226, all of which are suitable for production in the tropics.