Incorporation of the novel bacterial blight resistance gene Xa38 into the genetic background of elite rice variety Improved Samba Mahsuri.

Arra Yugander,Gouri Sankar Laha,Lella V Subba Rao,Jyothi Badri,Raman M Sundaram,Madamsetty Srinivas Prasad,Kuldeep Singh,Duraisamy Ladhalakshmi,Maganti Sheshu Madhav,Niranjan Baisakh

doi:10.1371/journal.pone.0198260

Arra Yugander, Gouri Sankar Laha + Show 8 more

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https://doi.org/10.1371/journal.pone.0198260

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Abstract

Bacterial blight (BB) in rice caused by Xanthomonas oryzae pv. oryzae (Xoo) is a major global production constraint, particularly in irrigated and rain-fed lowland areas. Improved Samba Mahsuri (ISM) is an elite, high-yielding, fine-grain type, BB-resistant rice variety possessing three BB-resistant genes (Xa21, xa13 and xa5) and is highly popular in the southern parts of India. As the BB pathogen is highly dynamic and the evolution of pathogen virulence against the deployed resistance genes is common, we added a novel BB-resistant gene, Xa38, into ISM through marker-assisted backcross breeding (MABB) to increase the spectrum and durability of BB resistance. The breeding line PR 114 (Xa38) was used as the donor for Xa38, whereas ISM was used as the recurrent parent. Foreground selection was conducted using PCR-based gene-specific markers for the target genes, whereas background selection was conducted using a set of polymorphic SSR markers between the parents and backcrossing that continued until the third generation. Eighteen homozygous BC3F2 plants possessing all four BB-resistant genes in the homozygous state and with a recurrent parent genome (RPG) recovery of more than 92% were identified and advanced to the BC3F6 generation. These 18 backcross-derived lines (BDLs) exhibited very high level of resistance against multiple Xoo strains and displayed agro-morphological traits, grain qualities and yield levels similar to or better than those of the recurrent parent ISM.

Highlights

Rice is considered essential for millions of Asians because of the immense influence on their culture, diets and economic condition and is the most important and dominant staple food crop in Asia [1]
At BC1F1, 87 of 160 plants were positive for Xa38, and the recovery of recurrent parent genome (RPG) among the positive BC1F1 plants ranged from 74.7% to 77.1%
These plants showed a very high level of bacterial blight (BB) resistance when inoculated with a virulent strain of Xanthomonas oryzae pv. oryzae (Xoo) (IX-220)

Summary

Introduction

Rice is considered essential for millions of Asians because of the immense influence on their culture, diets and economic condition and is the most important and dominant staple food crop in Asia [1]. 92% of rice is grown and consumed in Asia, which encompasses 55% of the world population [2]. One of the primary constraints in achieving this target is the increased incidence of several pests and diseases. Intensive cultivation practices involving the widespread cultivation of a few high-yielding rice varieties with a narrow genetic base coupled with heavy dependency on chemical fertilizers and pesticides and apparent changes in the climate have resulted in increased incidence of many diseases, including bacterial blight (BB) in rice [4]

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