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Progress in evolution of modern varieties

Progress in evolution of modern varieties
13
Jul

Process of progressive evolution of modern varieties

The process of evolution of modern varieties underway since 60s has been decisively progressive keeping in view the changing needs and priorities of the stakeholders in the rice sector, especially the grower, the consumer and the trader without, however, compromising on the productive semidwarf and fertilizer responsive plant type. The improvements have been broadly for crop duration to suit different crop seasons and cropping systems, grain quality to meet diverse consumer preferences and tolerance to biotic and abiotic stresses. Also, the successful breeding efforts included raising of the ceiling to yield through exploitation of hybrid vigour in China since late 70s and in a few countries outside China since mid 90s. It was the release of progressively improved varieties in quick succession and pace of replacement of old varieties of declining utility by new ones with distinct economic edge in terms of enhanced yield, higher resistance/tolerance against stresses or better grain quality that sustain high production growth across ecologies, regions and countries. But as some generalize the process of evolution of modern varieties was not in the order of yield, resistance to stresses, quality, etc. The order varied with the country with however, the productive semidwarf plant type remaining common to modern varieties of all generations. Whereas in China, which was taking advantage of short statured varieties since early 60s, the priority has been to breach the yield through hybrid technology, which it developed and started exploiting since late 70s. It is to be followed by super high yield varieties and hybrids, which China is experimenting with since late 90s. Its priority simultaneously has been for shorter duration, better grain quality and broad spectrum resistance to biotic stresses. In the tropical Asian countries outside China like India, breeding emphasis has been in the order of sustaining high yield through semidwarf plant type varieties but of different maturity to suit varied crop growing seasons and fine grain type with acceptable dry and flaky cooking quality till 70s followed overlappingly by resistance against insect pests and diseases from mid 70 onwards and improved plant type with tolerance to location specific abiotic stresses for different rainfed lowland and upland ecologies being continued seriously from early 80s and genetic yield enhancement through exploitation of hybrid vigour since Mid 90s. Likewise all the major rice growing countries in Asia have been engaged overlappingly with different breeding priorities giving due emphasis to high yield, disease insect pest resistance, better grain quality, reduced duration all in the semidwarf plant type background. In japonica rice growing Korea, Japan, Taiwan and northern China in Asia, the USA, Australia, Egypt and Near-east countries, breeding for high yield, milling and cooking qualities and resistance to blast disease has been the priority since beginning, while in O. glaberrima growing West and Central Africa for reasonably high yields and adaptation to moisture stress/problem soil conditions and resistance to pests. Relevance of varieties to a given situation, no matter they are traditional or modern, depends on how long since their release/introduction they remain popular with farmers/consumers. It is not uncommon that some of the of first generation varieties continue to remain popular in as late as fourth or fifth generation. For instance, Mahsuri a semitall, lodging prone variety of the pre-Green Revolution period is popular even after 40 years of its introduction. Same was the case with IR8 and Jaya, which remained popular for over 30 years occupying globally a sizeable area. Such slow pace of varietal replacement is quite common in rainfed and other harsh rice ecologies. For instance, Swarna, a variety found well adapted to rainfed shallow lowlands released in the 70s is still the most sought after variety in India and Bangladesh. But for such exceptions, it is the timely replacement of old varieties by more relevant new varieties that has been sustaining required production-productivity growth.

File Courtesy: 
FOUR DECADES OF RICE BREEDING – ACHIEVEMENTS, IMPACT, FUTURE DEMANDS AND STRATEGIES -Dr.E.A.Siddiq
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