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Innovative approaches to find new yield thresholds
Breeding efforts for yield enhancement have so far been through exploitation of easily accessible yield influencing variability resulting in dwarf plant type and new plant type based high yielding varieties and higher yielding hybrids in such plant type backgrounds, In search and use of yield related variability, efforts have so far been confined to cultivar genepool. It is the perception that needed variability is available in the cultivar genepool for targeted improvement, never prompted breeders to search for and use very large still not uncovered yield genes remaining hidden in the immediate progenitor and distantly related wild species and primitive land races. Convinced of the fact that in the origin, domestication, further differentiation and continued improvement of rice not all the variability had been captured of what originally present, search for still not identified gene sources was initiated using molecular marker technology. During the last 15 years several molecular marker linked yield related novel QTLs have been found to exist in the progenitor species and primitive cultivars by various laboratories in the world including in India. Research efforts are underway at present to stack the harmonious yield enhancing QTLs for exploring the prospects of raising further the genetic yield level. Molecular marker technology aside, possibilities of raising yield level by genetic manipulations involving alien gene sources are also being pursued in all seriousness in the national institutes. Manipulation of plant architecture, biosynthetic pathway of starch etc, are some of the strategies being attempted now.