Expression of a radish defensin in transgenic wheat confers increased resistance to Fusarium graminearum and Rhizoctonia cerealis

Abstract

Fusarium head blight (scab), primarily caused by Fusarium graminearum, is a devastating disease of wheat (Triticum aestivum L.) worldwide. Wheat sharp eyespot, mainly caused by Rhizoctonia cerealis, is one of the major diseases of wheat in China. The defensin RsAFP2, a small cyteine-rich antifungal protein from radish (Raphanus sativus), was shown to inhibit growth in vitro of agronomically important fungal pathogens, such as F. graminearum and R. cerealis. The RsAFP2 gene was transformed into Chinese wheat variety Yangmai 12 via biolistic bombardment to assess the effectiveness of the defensin in protecting wheat from the fungal pathogens in multiple locations and years. The genomic PCR and Southern blot analyses indicated that RsAFP2 was integrated into the genomes of the transgenic wheat lines and heritable. RT-PCR and Western blot proved that the RsAFP2 was expressed in these transgenic wheat lines. Disease tests showed that four RsAFP2 transgenic lines (RA1-RA4) displayed enhanced resistance to F. graminearum compared to the untransformed Yangmai 12 and the null-segregated plants. Assays on Q-RT-PCR and disease severity showed that the express level of RsAFP2 was associated with the enhanced resistance degree. Two of these transgenic lines (RA1 and RA2) also exhibited enhanced resistance to R. cerealis. These results indicated that the expression of RsAFP2 conferred increased resistance to F. graminearum and R. cerealis in transgenic wheat.

Susceptibility of Wheat Varieties to Soil-Borne <i>Rhizoctonia</i> Infection

“…The breading is the most promising measure to improve the tolerance to soil-borne pathogen complex, because the use of any xenobiotic has adverse effects on soil biota Hordeum vulgare rip30 increased tolerance (potato) [71] Hordeum vulgare chitinase increased tolerance (tobacco) [72] Pennisetum glaucum lipid transfer protein antifungal [73] Triticum sp. puroindoline increased tolerance (rice) [74] Celastrus hypoleucus pristimerin inhibiting the formation of infective body [75] Celastrus hypoleucus celastrol inhibiting the formation of infective body [75] Prokaryote 5-enolpyruvoyl-shikimate-3-phosphate synthetase Increased tolerance (wheat/Puccinia) [76] Oryza sativa thaumatin like protein increased tolerance (rice) [70] Oryza sativa OsPR-4b gene encoding pathogenesis related protein enhanced resistance [77] Solanum tuberosum Potide G proteinase inhibitor [78] Bacillus subtilis Iturin A Antifungal [79] Bacillus subtilis flagellin Antifungal [80] Raphanus sativus defensin increased tolerance (wheat) [81] Solanum tuberosum Snakin 1 enhanced resistance [82] Dasypyrum villosum unknown tolerance to AG 8 [83] Oryza sativa Rice chitinase increased tolerance (Musa/Mycosphaerella) [84] Oryza sativa Rice chitinase increased tolerance (Eleusine/Magnaporthe) [85] Tichoderma harzianum glucanase inhibiting the formation of infective body [86] Tephrosia villosa defensin increased tolerance (tobacco) [87] Arabidopsis thaliana NADPH oxydase induced resistance [88] Oryza sativa ACCA synthase induced resistance [89] as well as can predispose host plant to pathogen [62,63].…”

Susceptibility of winter Triticale Cultivars to Rhizoctonia Cerealis (sharp eyespot) and R. Solani

“…The available literature does not provide information on differences in susceptibility of triticale cultivars to R. cerealis. Studies have mostly concerned susceptibility of wheat or rice (Bateman et al 2000;Li et al 2011;Liu et al 2011). Nicholson et al (2002), Ray et al (2004) and Matusinsky et al (2008) found differences in DNA concentrations of R. cerealis which had colonized different cultivars of wheat.…”

“…Resistance to R. cerealis in wheat results mainly from the activity of peroxidase (Liu et al 2011). Transgenic wheat lines resistant to R. cerealis, with resistance that is environmentally independent and inherited for at least four generations, were developed in China after successfully integrating genes TiERF1, RsAFP2 and TaPIEP1 into the wheat genome (Chen et al 2008;Li et al 2011;Liu et al 2011). In Poland only eight wheat breeding lines completely resistant or highly resistant to infection by Oculimacula acuformis and O. yallundae causing true eyespot were bred.…”

“…Two possible strategies for decreasing sharp eyespot are application of fungicides and breeding for resistance (Bateman et al 2000;Hamada et al 2011;Li et al 2011). The former strategy may be less satisfactory because of the possibility of resistance development.…”

“…Traditional breeding techniques have so far not been useful, particularly since no mechanisms of resistance to Rhizoctonia have yet been identified. The advent of modern techniques of genetic modification, being developed mainly in wheat breeding (Ren et al 2007), raises some hopes (Li et al 2011).…”