Agromorphological diversity among wide-cross derived rice lines
2007
Quimio, C.A. | Mendez, N.P. | Escamos, S.H., Philippines Univ. Los Banos, College, Laguna (Philippines). Crop Sciences Cluster) | Masajo, T.M., Philippine Rice Research Inst., Los Banos, Laguna (Philippines)
In rice, leveling off in yield has been observed since the release of first semi-dwarf varieties that propelled the green revolution. One likely cause is the narrowing of the genetic base of parents going into the breeding program. Opportunity exists from segregating populations derived from interspecific crosses within rice. This was addressed by broadening the genetic base of PhilRice and UPLB rice breeding programs through wide hybridization. Crosses were made between O. sativa with O. barthii, O. glaberrima, O. longistaminata and O. rufipogon. Lines were generated from interspecific hybrid populations, backcrosses and intercrosses of selected individuals from where 192 lines were identified and maintained continuously to serve as parents in crosses made every season. These lines can be traced to one or more wild species parent with some having wild species cytoplasm and ranging in plant type from unimproved to fairly improved resulting from mild selection against obviously undesirable wild characters. Evaluation based on augmented design and analysis based on 39 traits showed highly significant variation among the lines and high diversity indices for qualitative and quantitative characters. Diversity indices were very high on important characters such as panicle length, grain weight, grain length, leaf width, culm number, culm diameter, culm length, days to heading and days to maturity. One line showed higher 100-grain weight than the check variety IR72. Analysis based on similarity coefficients grouped the lines into major clusters with distinct characteristics and which can be traced to a common wild parent. The report also discusses on the effect of mild selection on diversity among the lines.
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