Weedy rice (Oryza sativa L.) is one of the major issues of rice cultivation worldwide. In Italy it infests about 70% of the total rice area. Variable morphological and physiological traits permit to distinguish different weedy rice populations, however little is known about genetic differentiation and origin of Italian weedy rice populations. The objective of the study was to genetically characterize different Italian weedy rice populations selected on the basis of variable morphological traits. The main Italian rice territory was divided into 10 geographical areas in which 40 weedy rice populations were collected and grouped according to the awn traits. The populations were 25% awnless, 20% mucronate and 55% awned (30% black-awned and 25% straw-awned). After the seed collection, all the populations were sown in a same field and characterized morphologically on the basis of plant and seed traits. Genetic characterization using 20 SSR markers was performed on all the weedy rice populations and 20 rice cultivars, including some very old (late 19th century) nowadays no longer cultivated. ANOVA analysis showed that morphological plant and seed traits were significantly affected by the area of collection and awnedness group. The genetic analysis showed relatively low diversity among the tested populations, despite the overall Fst (0.1789), that indicated substantial differentiation among them. Upon STRUCTURE analysis performed on genetic distance, the populations clustered in three groups, with a separation between weedy rice and the cultivars. An UPGMA dendrogram, calculated out of the distance data obtained by the SSR analysis, showed similar grouping of the samples. Old cultivars showed similarity with weedy rice and clustered with it in both STRUCTURE and UPGMA analysis, suggesting a common origin.
Genetic diversity of Italian weedy rice populations
FOGLIATTO, SILVIA;VIDOTTO, Francesco;FERRERO, Aldo;
2012-01-01
Abstract
Weedy rice (Oryza sativa L.) is one of the major issues of rice cultivation worldwide. In Italy it infests about 70% of the total rice area. Variable morphological and physiological traits permit to distinguish different weedy rice populations, however little is known about genetic differentiation and origin of Italian weedy rice populations. The objective of the study was to genetically characterize different Italian weedy rice populations selected on the basis of variable morphological traits. The main Italian rice territory was divided into 10 geographical areas in which 40 weedy rice populations were collected and grouped according to the awn traits. The populations were 25% awnless, 20% mucronate and 55% awned (30% black-awned and 25% straw-awned). After the seed collection, all the populations were sown in a same field and characterized morphologically on the basis of plant and seed traits. Genetic characterization using 20 SSR markers was performed on all the weedy rice populations and 20 rice cultivars, including some very old (late 19th century) nowadays no longer cultivated. ANOVA analysis showed that morphological plant and seed traits were significantly affected by the area of collection and awnedness group. The genetic analysis showed relatively low diversity among the tested populations, despite the overall Fst (0.1789), that indicated substantial differentiation among them. Upon STRUCTURE analysis performed on genetic distance, the populations clustered in three groups, with a separation between weedy rice and the cultivars. An UPGMA dendrogram, calculated out of the distance data obtained by the SSR analysis, showed similar grouping of the samples. Old cultivars showed similarity with weedy rice and clustered with it in both STRUCTURE and UPGMA analysis, suggesting a common origin.
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