Abstract
The cultural practices of the early generations in a pedigree breeding programme may influence its success. The main objective of this study was to compare two selection environments in rice: Widely spaced planting in the field and dense planting in concrete basins. Both methods had yielded commercial varieties in the past. Two F2 populations (J and MS), derived from two crosses sharing the same female parent, were transplanted to both environments. Phenotypic traits were evaluated and their narrow sense heritabilities (h2) estimated in the F3 and in the F4 progenies of selected plants, all grown in the field. Growth potential was more apparent in the field for most traits, especially those related to yield, but broad sense heritabilities were higher in the basins for ten traits, being higher in the field for the other five. In population F2MS, field selection resulted in F3 plants which retained a higher tillering ability than those derived from basins selection. Most traits showed low h2 values: Additive variance was only relevant in panicle length (in both populations), plant height and mean panicle weight (in the J population). However, response to one generation of selection (from F3 to F4) also showed fixable variation in panicle number. In addition, this selection reduced plant height, increased culm diameter and internode length (in both populations), and improved pulling resistance (against lodging) in population J. It may be concluded that both practices can be used for selection in the F2, although different responses might be expected in yield related traits.
Highlights
IntroductionRice (Oryza sativa L.) breeding, even if conducted locally, may have a broader impact, because the grain yield of flooded rice under conventional cultivation does not present much significant difference in varietal ranking (genotype × environment interaction, G×E)within latitudinal ranges, if there are no biotic (pests or disease damages) nor abiotic (drought, salinity, toxicity or lack of oligoelements) stresses
Rice (Oryza sativa L.) breeding, even if conducted locally, may have a broader impact, because the grain yield of flooded rice under conventional cultivation does not present much significant difference in varietal rankingwithin latitudinal ranges, if there are no biotic nor abiotic stresses
Nine varieties were commercially released until 2014. Four of these crosses had their F2 selected in both environments: Three of their resulting varieties (‘Gavina’, ‘Cormorán’ and ‘Sivert’) came from an F2 mother plant selected in basins, and the fourth (‘JSendra’) had its F2 mother plant selected in the field
Summary
Rice (Oryza sativa L.) breeding, even if conducted locally, may have a broader impact, because the grain yield of flooded rice under conventional cultivation does not present much significant difference in varietal ranking (genotype × environment interaction, G×E)within latitudinal ranges, if there are no biotic (pests or disease damages) nor abiotic (drought, salinity, toxicity or lack of oligoelements) stresses. There are multiple examples: the Italian variety ‘Balilla’ (which was semi-dwarf and productive before the Green Revolution) was cultivated in the middle of the 20th century both in Italy and throughout Spain. Two Spanish varieties obtained from our Rice Department ( in IVIA) at the end of the 1960s were cultivated throughout Spain, but ‘Bahía’ in Italy (with the name of ‘Padano’) and Australia, while ‘Sequial’ was cultivated in Greece (with the name of ‘Hispaniki’). In the 1980s, two Californian varieties were widely cultivated in Spain and Italy: L202 (called ‘Thaibonnet’ in Spain) and M202 (called ‘Thainato’ in Spain). The Australian long-grained variety ‘Doongara’ corresponds likely to ‘Puntal’ in Spain, where it is still the rice variety most widely cultivated
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