Genetic Control of Resistance to the Sterol 14α-Demethylase Inhibitor Fungicide Prochloraz in the Cereal Eyespot Pathogen Tapesia yallundae

Abstract

Sexual crosses were used to determine the genetic basis of resistance to the sterol 14 ␣-demethylase inhibitor fungicide prochloraz in the cereal eyespot pathogen Tapesia yallundae. an even number of sensitive and resistant progeny. This indicated the segregation of a single major gene for resistance in each cross, which was confirmed by the use of backcrosses, crosses between F 1 progeny, and control crosses between sensitive parents. However, there was also evidence of additional quantitative genetic components responsible for the increased IG 50 s of the more resistant isolates. A further cross was made between isolate PR11 and an F 1 progeny arising from isolate 11-3-18, and this also yielded progeny which were entirely prochloraz resistant. This suggested that resistance genes were allelic in these two isolates, with resistance conferred by a gene at the same locus (or closely linked loci), despite the fact that the isolates (PR11 and 11-3-18) originated from different continents.A major reason for the continued success of agricultural production in the developed world has been the availability of chemicals to control pests and diseases in crops. Of these, the sterol 14 ␣-demethylase inhibitor (DMI) fungicides represent the largest and most important group of modern antifungal compounds, possessing excellent protectant, curative, and eradicant properties against a wide range of fungal species (35). Most DMI fungicides are derivatives of imidazoles or triazoles and have remained highly effective in most field applications despite many years of intense agricultural use and their singlesite mode of action. However, decreased sensitivity and field resistance to certain DMIs has been reported in at least 13 species of plant pathogen (10).The imidazole prochloraz (1-{N-propyl-N-[2-(2,4,6-trichlorophenoxy)ethyl]carbamoyl}-imidazole; trade name, Sportak) was launched in 1977 and has since been registered for use on more than 30 different crops in 50 countries worldwide (37; Prochloraz-technical information,

Presence and Functionality of Mating Type Genes in the Supposedly Asexual Filamentous Fungus Aspergillus oryzae

“…Specific examples include selection for flocculation in Saccharomyces cerevisiae, increased alkaloid production in Claviceps purpurea, improved thermotolerance in Pleurotus species, and investigation of resistance to fungicides in Tapesia yallundae (13,17,53). It is hoped that future research with A. oryzae might lead to a "sexual revolution" in this species, as seen for other aspergilli previously assumed to be asexual (15,47), thus providing an important new method for strain improvement in this widely utilized industrial fungus.…”

“…After 24 h of growth, 200 mg of mycelia was shifted onto DPY agar medium covered with a cellulose acetate membrane (Membrane Filter; Advantec Toyo, Tokyo, Japan) and was further cultivated for 48 h. Total RNA was extracted as described previously (32), followed by treatment with DNase I (TaKaRa, Otsu, Japan). First-strand cDNAs were synthesized with ReverTra Ace reverse transcriptase (Toyobo, Osaka, Japan) using oligo(dT) [12][13][14][15][16][17][18] (Invitrogen) as the primer. Quantitative real-time PCRs (qRT-PCRs) were performed using a LightCycler FastStart DNA Master SYBR green I system (Roche Diagnostics, Indianapolis, IN) as instructed by the manufacturer.…”

Fungicide Resistance of Gibberella fujikuroi Isolates Causing Rice Bakanae Disease and Their Progeny Isolates

“…Prochloraz는 DMI계(sterol 14 α-demethylase inhibitor) 살균제로 1977년 처음 사용되어 세계적으로 약 50개국에서 30종 이상의 작물에 사용되고 있다 (Dyer et al, 2000). 그러나 맥류 eyespot을 일으키는 Oculimacula acuformis (Leroux and Gredt, 1997)와 목화의 verticillium 시들음병을 일으키는 Verticillium dahliae 등에서 저항성 균주가 보고되었다 (Kurt et al, 2003).…”

“…여러 가지 benzimidazole계 살균제 저항성 식물병원균과 같이 약제 효과가 갑자기 감소하는 것은 단일 주동 유전자 (single major gene)의 돌연변이에 의해 나타나거나 혹은 두 개의 저항성 유전자의 동반 상승효과에 의해 나타날 수 있다. 반면, 병원균 집단에서 감수성의 점진적인 이동은 다원유전자 (polygene)가 관여하는 것으로 알려져 있다 (Dyer et al, 2000). 국내에서 벼키다리병 방제를 위한 종자소독제로 prochloraz *Corresponding author <E-mail : hyon338@korea.kr> 가 오랫동안 사용되어 왔으나 최근 키다리병의 발생이 증가 하고 일부 지역의 경우, 방제효과가 감소하고 있어 약제저항성 균주에 대한 연구의 필요성이 대두되고 있다 (신 등a, 2008 …”

Detection of Fungicide Resistance

“…Usually, resistant individuals are detected using bioassays (sensitivity tests or poison plate assays) and those resistant isolates may be correlated with molecular markers, many of which are based upon previous studies (Koernraadt et al 1992;Albertini et al 1999;Schnabel and Jones, 1991;Lesniak et al 2011). In some instances, segregation analysis between crosses of sensitive and resistance phenotypes is often used to strengthen this correlation (Faretra and Pollastro 1993;Orth et al 1995;Dyer et al, 2000); however, the ultimate mechanism of resistance is often lacking. Ultimately, the success of molecular detection is only useful if the expected genetic profile that is being screened correlates to the phenotype of resistance.…”