Yearly changes in virulence of Phakopsora pachyrhizi isolates in Paraguay

IF 2.5 3区 农林科学 Q2 Agricultural and Biological Sciences
Ruth Scholz, Marta Alicia Fernández Gamarra, María José Vargas, Naoki Yamanaka
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引用次数: 0

Abstract

Asian soybean rust (ASR), caused by the pathogen Phakopsora pachyrhizi, is one of the most notable soybean diseases in Paraguay because of the associated productivity losses and expenditures related to fungicide use. There is also concern regarding the environmental impact of excessive fungicide use. In addition, the decreased sensitivity of ASR pathogens to various fungicide groups has been reported in recent years. To effectively control ASR, it is necessary to combine fungicides with resistant varieties. To introduce ASR resistance genes (Rpp: Resistance to P. pachyrhizi) into Paraguayan soybean cultivars, the effectiveness of Rpp resistance genes must be determined, as a few are rendered ineffective due to virulence changes in the pathogen population. In this study, the effectiveness of 12 different soybean genotypes with different Rpp genes was evaluated using 18 P. pachyrhizi samples obtained in the 2016/17, 2017/18, 2018/19, and 2019/20 seasons and compared with the previous eight seasons from 2007 to 2015. Yearly changes in virulence were observed in a few differentials; however, these changes were not always from avirulent to virulent. Further, all differential varieties with a single resistance gene showed resistant phenotypes in less than 50 % of the samples in their least effective years. Considering these observations, the introduction of a single resistance gene poses a risk in breeding for ASR resistance. The differentials carrying a single gene, Rpp1-b or Rpp5, tended to show high frequencies, specifically 86.9–89.8 % resistance in the tested samples from 2007–2019, and that of the Rpp-pyramided line carrying Rpp2 + Rpp4 + Rpp5 was 97.0 %. Therefore, the introduction of two or more resistance genes, via combination with Rpp1-b and/or Rpp5, or the introduction of Rpp2 + Rpp4 + Rpp5 would be effective and durable for mitigating the Paraguayan ASR pathogen.

Abstract Image

巴拉圭 Phakopsora pachyrhizi 分离物毒力的逐年变化
由病原体 Phakopsora pachyrhizi 引起的亚洲大豆锈病(ASR)是巴拉圭最显著的大豆病害之一,因为它会造成相关的生产力损失和与杀菌剂使用相关的支出。过度使用杀菌剂对环境的影响也令人担忧。此外,据报道,近年来 ASR 病原体对各类杀菌剂的敏感性有所下降。为了有效控制 ASR,有必要将杀菌剂与抗性品种相结合。要在巴拉圭大豆栽培品种中引入 ASR 抗性基因(Rpp:对 P. pachyrhizi 的抗性),必须确定 Rpp 抗性基因的有效性,因为病原体种群的毒力变化会导致少数基因失效。在本研究中,利用 2016/17、2017/18、2018/19 和 2019/20 年度获得的 18 个 P. pachyrhizi 样本,评估了带有不同 Rpp 基因的 12 种不同大豆基因型的有效性,并与 2007 至 2015 年的前 8 个季节进行了比较。在一些差异品种中观察到了毒力的年度变化;然而,这些变化并不总是从无毒到有毒力。此外,所有具有单一抗性基因的差异品种在其抗性最弱的年份都有不到 50% 的样本表现出抗性表型。考虑到这些观察结果,引入单一抗性基因会给抗 ASR 育种带来风险。携带单一基因 Rpp1-b 或 Rpp5 的差系往往表现出较高的抗性频率,特别是在 2007-2019 年的测试样本中,抗性频率为 86.9-89.8%,而携带 Rpp2 + Rpp4 + Rpp5 的 Rpp-pramided品系的抗性频率为 97.0%。因此,通过与 Rpp1-b 和/或 Rpp5 结合引入两个或更多抗性基因,或引入 Rpp2 + Rpp4 + Rpp5 将有效且持久地减轻巴拉圭 ASR 病原体的危害。
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来源期刊
Tropical Plant Pathology
Tropical Plant Pathology PLANT SCIENCES-
CiteScore
4.50
自引率
4.00%
发文量
61
审稿时长
6-12 weeks
期刊介绍: Tropical Plant Pathology is an international journal devoted to publishing a wide range of research on fundamental and applied aspects of plant diseases of concern to agricultural, forest and ornamental crops from tropical and subtropical environments.  Submissions must report original research that provides new insights into the etiology and epidemiology of plant disease as well as population biology of plant pathogens, host-pathogen interactions, physiological and molecular plant pathology, and strategies to promote crop protection. The journal considers for publication: original articles, short communications, reviews and letters to the editor. For more details please check the submission guidelines. Founded in 1976, the journal is the official publication of the Brazilian Phytopathology Society.
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