Rice Genetic Improvement Odyssey of Past Centuries
Posted on October 17th, 2021

by M. P. Dhanapala Former Director, Rice Research and Development Institute, Batalagoda Courtesy The Island

History is important. It keeps you away from reinventing the wheel and repeating the mistakes already committed in the past. In history, there should not be hidden expressions to read between lines as the ten giants of King Dutugamunu were fed with traditional rice,”concealing the details of what the others were eating and why they were not giants or that we have been exporting rice during the past in such and such era” without disclosing the quantities and the recipient countries. For that matter if you go through the export details, we do export rice even now.

The green revolution was criticized as the contributing factor for the so called unidentified Kidney Disease of Unknown Origin (CKDu) which was reported primarily from the North Central Province. Whatever the causal factor of CKDu is, Norman Borlaug or his green revolution has nothing to do with the kidney disease or rice in Sri Lanka. It is true that his innovative ideology in wheat breeding induced the rice breeders worldwide to develop aphysiologically efficient rice plant type by changing the plant stature and canopy characteristics. The Sri Lankan rice varieties were developed within the country, by the Sri Lankan scientists. It was an extension of the breeding process initiated by the British scientists during the colonial era. The progress of rice breeding from its inception by different generations will be unfolded in this write-up to judge the calculated decisions taken by the ancestral breeders to improve rice productivity in the country.

I would like to lay the baseline from a report published by Edward Elliott, a British Civil Servant in 1913. (Tropical Agriculturist, Vol. XLI, No. 6, Dec. 1913). He states that the forced labor (Rajakariya) that existed then was abolished in 1832. Subsequently, the communal cooperation system (Atththam) also ceased to exist gradually. These two incidents were cited as the major reasons for the neglect of irrigation structures and subsequent decline of rice production in the mid 19th Century. The annual rice production estimated for the period of 10 years ending in 1856 was 5.5 million bushels, the lowest in the recorded history.

Enacting the Paddy Ordinance in 1857 allowed voluntary restoration of old irrigation structures which eventually led to the gradual increase in the cultivated extent and the annual rice production. Estimated rice production data during this era and at the turn of the century are summarized in Table 1. The original data were in acres and bushels. The data were transformed into hectares and kilograms and tonnes assuming 20 kg as the bushel weight. The transformed data in Table 1 appear within parentheses.

See table 1.

Annual rice production statistics from thelatter half of the 19th and early 20th Century (Elliot, 1913)

The rice production data above are estimates based on returns from paddy, probably grain tax, in the Government Blue Books. You may realize that these estimates are sometimes too high when actual data appear towards 1940s. However, at the turn of the 19th Century, the rice varieties were exclusively traditional types maintained by farmers and the Department of Agriculture was not established.

Many critics maintain that we had innumerable different varieties of rice in the past. The earliest recorded in the history was a collection of 300 rice varieties displayed by Nugawela Dissawe for the agri-horticultural exhibition held in 1902 (Molegoda, 1924) (Trop. Agric. XLII (4): 218-224.). This probably represented almost all the cultivars in the field during this period. This was the largest collection of rice varieties in the recorded history in Ceylon, leaving out the recent collections performed in the latter half of the 20th century. Molegoda explains very comprehensively the status of rice varieties and the procedure followed in naming them.

The rice cultivation at the beginning of 20th century was entirely organic manure dependent. The farmers then were apparently more competent in traditional methods of rice cultivation. The most striking feature during this era was that the average yields were below one ton/ha (<20 bu/ac) even in the best productive year, 1903 (Table 1).

In 1914, an encouraging note on Extension of Paddy Cultivation by A. W. Beven (Trop. Agric. XLIII (6): 421-424.) appears with the suggestion of seed selection to improve rice yields. He states that in the year 1913 the yield estimate of 9,622,320 bushels was too high atarget, i.e.14.2 bu/ac (0.71 t/ha), for the cultivated extent of 671,711ac (271,827ha), but suggests that with seed selection accompanied by proper land preparation, manuring and transplanting, the yields could be increased up to 25 bu/ac (1.25t/ha). This suggestion was at the inception of the Department of Agriculture which was established in 1912.

The earliest record on rice varietal improvement dates back to seed selection in 1914 by Dr. Lock at Peradeniya. This was done more or less parallel with the establishment of Johannsen’s pure line theory (1903). In the literature, Dr. Lock’s improved Hatial (a seven month variety) appears from time to time as a standard variety in yield tests.

The next most important step was the pure-line selection. Initially, three Economic Botanists, F. Summers (1921), R.O. Iliffe (1922), L. Lord (1927) and at latter stages Paddy Officer G.V. Wickremasekera were involved in the selection of pure- lines (Trop. Agric. LVIII (2): 67-70; Trop. Agric. LXVIII (5): 309-318). Pure-line selection exploited heterogeneity within the farmer maintained traditional rice cultivars. Each cultivar composed of different types within it. As a result, individual plant selection within cultivars produced progenies with better genetic potential, but resembling the mother plant selected; they bred true to type as rice is an obligate inbreeder. This was the essence of pure-line theory established by Johannsen (1903).

Pure-line selection was initiated with a representative collection of traditional varieties. The most popular varieties were included in the process. Pure-line selection was done at two major locations, Mahailluppallama and Peradeniya. Subsequently, selection was regionalized to accommodate regionally adapted varieties in the process. The best isolated progenies were tested at 19 test locations in different agro-ecological regions for adaptability, prior to recommendation. The best adapted pure-lines (21 lines – Table 2) were identified for purity maintenance at four different paddy stations – Ambalantota (nine lines), Mahailluppallama (eight lines), Madampe (two lines) and Batalagoda (two lines). Further multiplication of seeds was done in government farms under the supervision of Agricultural Officers and distributed as seed paddy for cultivation (Trop. Agric. CIV (2): 97-98.).

See table 2.

Pure-line varieties identified for cultivation (Extract from Amended Departmental Circular No. 156 – Trop. Agric. CIV (2): 97-98.)

While the pure-line selection process was on, Joachim (1927) (Trop. Agric. LXIX 137) warned that the sustenance of increased yields by cultivation of high yielding pure-lines has to be met with liberal manuring. However, despite of all these attempts during the two decades from 1920s, the paddy yields were not substantially increased (Table 3). Rice yield data presented in Table 3 shows lower values compared to yield estimates from Government Blue Books presented in Table 1. The data in Table 3 being more reliable, the Table 1 data could be overestimates.

However, the majority of the harvested rice crop in the 1940s could be from potentially better pure-line selections, but the yields were much below the anticipated levels. The total production was around 15 million bushels (0.3 m tons) and yields stagnated ataround 14 bu/ac (0.7 t/ha).

The Draft Scheme for Development of the Paddy Industry in Ceylon drawn in 1945 (Trop. Agric. CI (3) 191-195) begins with the statement that only a third of the annual requirement is met by the local rice production.

The balance was imported; the population was less than seven million during that period and the paddy cultivation was done organically with the best adapted pure-lines of traditional cultivars, though it failed to deliver what was intended.

The importance of inorganic (chemical) fertilizer was felt during this period as the only option to improve paddy yields further. Use of sodium nitrate (Na NO3) as the source of nitrogen (N) was attempted in rice prior to 1905 based on American experience in soybean cultivation, but nitrite (NO2) toxicity under reduced conditions in submerged paddy soils prohibited its use. Superiority of NH4 form of N was demonstrated by Nagaoka (1905) and Daikuhara and Imaseki (1907). However, the application of N promoted vegetative growth in pure-lines derived from traditional rice varieties causing premature lodging. Furthermore, two fungal diseases, blast and brown spot, became prominent. Around this period some introduced varieties were tested without much success. Among them, Ptb 16 from Pathambi, India, popularly called Riyan wee, with long panicles and slender grains (Buriyani rice) became popular, but self sufficiency in rice appeared to be far away.

Transition to another phase in rice breeding began as the rice breeders over the world employed cross-bred populations to create genetic variability to bring together desirable characteristics of different rice cultivars to develop better varieties. Rice hybridization techniques were developed around early 1920s and a major break through in changing the plant-type was accomplished in Japan with the use of Jikkoku, a dwarf natural mutant of Japonica rice. The performance of Japonica varieties exhibited substantial improvement with this transition. Influenced by the Japanese experience, the Food and Agriculture Organization sponsored a cross breeding program of Japonica with Indica rices in Cuttak, India to change the Indica plant type too in this direction, but without success due to incompatibility between the two groups (Japonica and Indica) leading to grain sterility in subsequent generations.

In Sri Lanka, the first paper on rice hybridization techniques was published in 1951 by J.J. Niles, an assistant in Economic Botany, guided by Prof. M. F. Chandraratne, the Economic Botanist (Trop. Agric. CVII (1):25-29.). Prof. Chandraratne was instrumental in initiation of rice hybridization. Simultaneously rice hybridization work began at the Dry Zone Agricultural Research Station at Mahailluppallama under the guidance of Dr. Ernest Abeyratne. The Central Rice Breeding Station, Batalagoda was established in 1952 and Dr. H. Weeraratne was transferred from Mahailluppallama to Batalagoda as the rice breeder with the hybrid populations already developed at Mahailluppallama.

Dr. Weeraratne, influenced by his superiors, Prof. Chandraratne and Dr. Abeyratne, continued rice hybridization to create genetic variability for selection. The hybridization techniques adopted by him were published in 1954 (Trop. Agric. CX (2) 93-97). Apparently, the labor intensive pedigree method was employed by Dr. Weeraratne to identify and fix desirable genotypes from segregating populations. And this was the beginning of theH” series of varieties that revolutionized the rice sector in Sri Lanka. The letter H” was used to imply that the varieties were of hybrid origin and were different from traditional varieties or pure-lines, but not to imply that they are hybrids.

Fig. 1,

The Central Rice Breeding Station, Batalagoda, Department of Agriculture

The first of the series, H4 (4.5 month, red bold), released in 1957, reached its peak popularity after a five year lapse of time and covered over 60% of the cultivated extent in Maha season, 62/63. The others in the series were H7 (3.5 month, white bold), H8 (4.5 month, white samba), H9 (5-6 month, white bold), H10 (3 month, red bold). Release of H varieties (1) minimized crop losses due to blast disease, (2) changed rice cropping pattern from single to double cropping, (3) use of N fertilizer increased by 350% due to their moderate response to fertilizer, (4) increased national yield level up to 3.5 t/ha (Senadhira et. al., Rice Symposium, Department of Agriculture, 1980). This effort, though appreciated widely, fell short of self sufficiency again.

The most controversial phase for the critics in rice breeding was initiated in mid 1960s, while H” varieties were replacing the pure-lines and the traditional varieties from paddy fields. The International Rice Research Institute was established in 1960 and the plant physiologists conceptualized the plant type structure of rice to make it physiologically efficient. The development of H” varieties (Old Improved Varieties) abruptly ended with these new innovations.

The breeders responsible for developing this new plant type in Sri Lanka, specifically the Bg varieties, were Dr. H. Weeraratne, Dr. N. Vignarajah, Dr. D. Senadhira and Mr. C.A. Sandanayake. None of them are among us any more. I joined the team in the late 1960s, at the tail end of H varieties and continued the process till the country reachedthe brim of self reliance in rice.

The Bg and other modern varieties are physiologically efficient. They are devoid of unproductive plant tissues and ineffective tillers. The plant structure is designed to reduce mutual shading of leaves and trap solar radiation effectively by every leaf in the canopy thus reducing the respiratory losses and promoting the net assimilation rate. They out yield traditional and H varieties at any level of soil fertility and show positive grain yield response to added fertilizer. They are lodging resistant and incorporated with resistance/tolerance to major pests and diseases prevalent in the country. More preciously, we have reversed the source-sink relationship of the rice plant to translocate photosynthates to produce more grains and less straw. The potential yield of improved varieties exceeds 6t/ha. All these traits listed above have been tested in controlled experiments in the field to confirm the superiority of new improved varieties. We reap around 4.5 tons/ha as our national average yield at present; the country is self sufficient in rice, the dream every political leader had since independence.

This in anut shell is what the rice breeders have accomplished and for which they were given the title Kumbandayas” in an article written apparently by a medical professional. The local rice scientists embark only on innovations backed by scientific facts. They do not have to exaggerate or lie. They know little more than those who seek cheap popularity by being critical about the accomplishments of rice scientists. This country needs people dedicated and confined to their respective professions allowing other professionals to play their own role. At any time rice breeders can take the country back to thetraditional rice era if you want to begin all over again from the beginning. The traditional accessions are in long-term storage at the Plant Genetic Resource Center (PGRC), Gannoruwa, Department of Agriculture, and can be taken out for multiplication at any time as the seed samples are viable.

Now I repent why we produced rice with more grains and less straw. There appears to be unsatisfied demand for straw. I like to conclude this disclosure with a statement made by Dr. N. M. Perera at the University of Ceylon, Peradeniya in the mid 1960s. Comrade, I can give you facts and figures, but I am sorry; I am unable to implant a brain in you”.

Email: maddumadhanapala@yahoo.com

(The writer holds a Ph D, Genetics and Plant Breeding, North Dakota University, USA, 1990, M Sc., Plant Breeding, Saga University, Japan, 1978 and B sc. Agric. University of Ceylon, Sri-Lanka, 1968. He has served as Research Officer, Rice Breeding (1969 – 1995) Central Rice Breeding Station, Batalagoda, Director, Rice Research and Development Institute, (1996 – 2000), Batalagoda, Affiliate Scientist, International Rice Research Institute (2000 – 2003), Philippines and Technical Advisor, JICA,, Tsukuba International Center, (2004 – 2012), Japan)

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