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J Fungi (Basel). 2018 Jun 14;4(2). pii: E71. doi: 10.3390/jof4020071.

The Caryopsis of Red-Grained Rice Has Enhanced Resistance to Fungal Attack.

Author information

1
Council for Agricultural Research and Economics-Research Centre for Genomics and Bioinformatics, via S. Protaso 302, 29017 Fiorenzuola d'Arda (PC), Italy. alberto.gianinetti@crea.gov.it.
2
Council for Agricultural Research and Economics-Research Centre for Genomics and Bioinformatics, via S. Protaso 302, 29017 Fiorenzuola d'Arda (PC), Italy. franca.finocchiaro@crea.gov.it.
3
Council for Agricultural Research and Economics-Research Centre for Genomics and Bioinformatics, via S. Protaso 302, 29017 Fiorenzuola d'Arda (PC), Italy. fabio.maisenti@studenti.unipr.it.
4
Council for Agricultural Research and Economics-Research Centre for Genomics and Bioinformatics, via S. Protaso 302, 29017 Fiorenzuola d'Arda (PC), Italy. satsapdailly@yahoo.fr.
5
Council for Agricultural Research and Economics-Research Centre for Genomics and Bioinformatics, via S. Protaso 302, 29017 Fiorenzuola d'Arda (PC), Italy. caterina.morcia@crea.gov.it.
6
Council for Agricultural Research and Economics-Research Centre for Genomics and Bioinformatics, via S. Protaso 302, 29017 Fiorenzuola d'Arda (PC), Italy. roberta.ghizzoni@crea.gov.it.
7
Council for Agricultural Research and Economics-Research Centre for Genomics and Bioinformatics, via S. Protaso 302, 29017 Fiorenzuola d'Arda (PC), Italy. valeria.terzi@crea.gov.it.

Abstract

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.

KEYWORDS:

germination; grain mycotoxins; pigmented rice; proanthocyanidins; red rice; seed fungal infection; seedling growth

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