ABSTRACT
Weedy rice is a representative of the extensive group of feral weeds that derive from crops, but has returned to the lifestyle of a wild species. These weeds develop either from a hybridization of crops with wild relatives (exoferality), or by mutation of crops to weedy forms (endoferality). Due to the close relation of weed and crop, the methods for weed-targeted containment are limited to date. A deeper understanding of the development of such weeds might help to design more efficient and sustainable approaches for weed management. Weedy rice poses a serious threat to rice yields worldwide. It is widely accepted that weedy rice has originated independently in different regions all over the world. However, details of its evolution have remained elusive. In the current study, we investigated the history of weedy rice in northern Italy, the most important rice-growing area in Europe. Our approach was to analyze genes related to weedy traits (SD1, sh4, Rc) in weedy rice accessions compared to cultivars, and to integrate these results with phenotypic and physiological data, as well as historical information about rice farming in Italy. We arrive at a working model for the timeline of evolution of weedy rice in Italy indicating that both exoferality and endoferality acted as forces driving the development of the diverse weedy rice populations found in the region today. Models of weed evolution can help to predict the direction which weed development might take and to develop new, sustainable methods to control feral weeds.
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. Different Weedy Rice populations can be distinguished based on variable morphological and physiological traits; however, little is known about genetic differentiation and origin of Italian weedy rice populations. The objective of this study was to genetically and morphologically characterize and compare different Italian weedy rice populations selected on the basis of different phenotypes. 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. All the individuals of the populations were morphologically characterized according to plant and seed traits. Genetic characterization was performed using 19 SSR markers on all the collected accessions, and several rice cultivars, including some very old (late 19th century), nowadays are no longer cultivated. ANOVA showed that morphological plant and seed traits were significantly affected by the collection area and awnedness group. The importance of the awn morphology was also reflected in the Bayesian clustering where, despite a relatively low genetic diversity, the clusters displayed different awn types. An UPGMA dendrogram confirmed the clusters detected in STRUCTURE analysis and also revealed a grouping of certain old cultivars with the weedy rice, suggesting a common origin.
ABSTRACT
Two putative adhesion genes of the potentially probiotic strain Lactobacillus plantarum BFE 5092, i.e., a gene with similarity to an aggregation-promoting factor gene apf5092, and the mucin-binding protein gene mub5092, were investigated in this study. The gene encoding apf5092 encoded a protein bearing a predicted 26 amino acid signal peptide and a LysM domain putatively involved in binding to peptidoglycan. Moreover, the deduced protein also showed an amino acid sequence characteristic of an aggregation-promoting factor. The genes were tested for expression under different environmental conditions, and transcriptional studies on apf5092 showed that the expression could be influenced by low temperature and pH within 30 min. The aggregation behavior of the cells also changed at the low pH condition, but less noticeably at low temperature. To further investigate the role of apf5092 in aggregation, it was cloned and expressed in E. coli. The transformed strain showed higher co-aggregation ability with Gram-positive bacteria. Transcription studies on mub5092 revealed that it could be induced by mucin when added to the growth medium within 30 min. The data suggested that L. plantarum BFE 5092 can quickly adapt to changing environmental conditions and that enhanced aggregation may be important to survive low pH conditions, e.g., of the stomach or of fermented foods, and may thus be an important colonization factor.
