Rice quality is mainly related to the following two starch components, apparent amylose content (AAC) and resistant starch (RS). The former affects grain cooking properties, while RS acts as a prebiotic. In the present study, a Genome Wide Association Scan (GWAS) was performed using 115 rice japonica accessions, including tropical and temperate genotypes, with the purpose of expanding the knowledge of the genetic bases affecting RS and AAC. High phenotypic variation was recorded for the two traits, which positively correlated. Moreover, both the parameters correlated with seed length (positive correlation) and seed width (negative correlation). A correlational selection according to human preferences has been hypothesized for the two starch traits and grain size. In addition, human selection has been proposed as the causal agent even for the different phenotypes related to starch and grain size showed by the tropical and temperate japonica accessions utilized in this study. The present GWAS led to the identification of 11 associations for RS on seven chromosomes and five associations for AAC on chromosome 6. Candidate genes and co-positional relationships with quantitative trait loci (QTLs) previously identified as affecting RS and AAC were identified for 6 associations. The candidate genes and the new RS- and/or AAC-associated regions detected provide valuable sources for future functional characterizations and for breeding programs aimed at improving rice grain quality.

Red rice fully dormant seeds do not germinate even under favorable germination conditions. In several species, including rice, seed dormancy can be removed by dry-afterripening (warm storage); thus, dormant and non-dormant seeds can be compared for the same genotype. A weedy (red) rice genotype with strong dormancy was used for mRNA expression profiling, by RNA-Seq, of dormant and non-dormant dehulled caryopses (here addressed as seeds) at two temperatures (30 °C and 10 °C) and two durations of incubation in water (8 h and 8 days). Aim of the study was to highlight the differences in the transcriptome of dormant and non-dormant imbibed seeds. Transcript data suggested important differences between these seeds (at least, as inferred by expression-based metabolism reconstruction): dry-afterripening seems to impose a respiratory impairment onto non-dormant seeds, thus glycolysis is deduced to be preferentially directed to alcoholic fermentation in non-dormant seeds but to alanine production in dormant ones; phosphoenolpyruvate carboxykinase, pyruvate phosphate dikinase and alanine aminotransferase pathways appear to have an important gluconeogenetic role associated with the restoration of plastid functions in the dormant seed following imbibition; correspondingly, co-expression analysis pointed out a commitment to guarantee plastid functionality in dormant seeds. At 8 h of imbibition, as inferred by gene expression, dormant seeds appear to preferentially use carbon and nitrogen resources for biosynthetic processes in the plastid, including starch and proanthocyanidins accumulation. Chromatin modification appears to be a possible mechanism involved in the transition from dormancy to germination. Non-dormant seeds show higher expression of genes related to cell wall modification, suggesting they prepare for acrospire/radicle elongation.

Control methods alternative to synthetic pesticides are among the priorities for both organic and conventional farming systems. Plants are potential sources of compounds with antimicrobial properties. In this study, the antifungal potentialities of saponins derived from Medicago species and oat grains and of brassica sprouts have been explored for the control of Verticillium dahliae, a widely distributed fungal pathogen that causes vascular wilt disease on over 200 plant species. All the tested plant extracts showed antifungal properties. Such compounds, able to reduce mycelium growth and conidia formation, deserve deeper in vivo evaluation, even in combination with a delivery system.

Seed persistence in the soil is threatened by microorganisms, but the seed coat helps protect the seed from them. Although modern rice (Oryza sativa L.) cultivars have a whitish caryopsis, some varieties have a red caryopsis coat, a trait typical of wild Oryza species. The red colour is due to the oxidation of proanthocyanidins, a class of flavonoids that is found in the outer layers of the seed in many species. We aimed to assess whether these natural compounds (proanthocyanidins and proanthocyanidin-derived pigment) have some protective effect against microbial attacks. Dehulled caryopses of white-grained and red-grained rice genotypes were employed to assay fungal infection. Specifically, three white-grained rice cultivars (Perla, Augusto, and Koral) and three red-grained rice varieties (Perla Rosso, Augusto Rosso, and Koral Rosso) were used. In a first test, the caryopses were infected with Epicoccum nigrum at 10 °C, and seedling growth was then assessed at 30 °C. In a second test, the degree of infection by the mycotoxigenic fungus Fusarium sporotrichioides was assayed by measuring the accumulation of T-2/HT-2 toxins in the caryopses. Infection was performed at 10 °C to prevent rice germination while allowing fungal growth. In both the tests, red caryopses showed reduced, or delayed, infection with respect to white ones. One black-grained cultivar (Venere) was assayed for the accumulation of T-2/HT-2 toxins as well, with results corresponding to those of the red-grained rice varieties. We argue that the red pigment accumulating in the caryopsis coat, and/or the proanthocyanidins associated with it, provides a protective barrier against challenging microorganisms.