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<p>Bacterial leaf blight (BLB), caused by <i>Xanthomonas oryzae pv. oryzae</i> (Xoo), is one of the most destructive diseases of rice and poses a serious threat to productivity in the humid and flood-prone ecosystems of northeastern India. The short-duration rice cultivar Luit is widely cultivated in Assam because of its early maturity and adaptability; however, its susceptibility to BLB limits yield stability under disease-prone conditions. The present study aimed to improve BLB resistance in Luit through marker-assisted pyramiding of three major resistance genes, <i>Xa21</i>,<i> xa13</i>, and <i>xa5</i>. A marker-assisted backcross breeding approach was employed using IRBB60 as the donor parent. Gene-specific functional markers were used to track the target resistance genes, while polymorphic SSR markers were employed to assess recurrent parent genome recovery. Screening of the BC₂F₂ population identified 57 plants homozygous for all three resistance genes. The selected pyramided plants exhibited recurrent parent genome recovery ranging from 81.25% to 93.84% and retained the key agronomic characteristics of Luit, including early flowering, maturity duration, and grain yield. The resistance response of the pyramided plants was evaluated against three virulent Xoo isolates representing different agro-climatic regions of Assam. Plants carrying all three resistance genes consistently exhibited shorter lesion lengths than plants carrying one or two resistance genes and showed resistance levels comparable to those of the donor parent IRBB60. Several pyramided plants combined high levels of BLB resistance with high recurrent parent genome recovery and desirable agronomic performance. These findings demonstrate that marker-assisted pyramiding of <i>Xa21</i>,<i> xa13</i>, and <i>xa5</i> is an effective strategy for improving BLB resistance in the genetic background of Luit. The selected pyramided materials provide valuable genetic resources for further evaluation and utilization in rice improvement programmes targeting BLB-prone environments.</p>

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Marker-assisted pyramiding of bacterial leaf blight resistance genes (Xa21, xa13 and xa5) in a short-duration rice cultivar Luit

  • 期刊论文

  • 发表日期：

    2026年6月30日

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  • Sushil Kumar Singh,
  • Dhananjay Kumar,
  • Sanjay Kumar Chetia,
  • Mahendra Kumar Modi

摘要

Bacterial leaf blight (BLB), caused by Xanthomonas oryzae pv. oryzae (Xoo), is one of the most destructive diseases of rice and poses a serious threat to productivity in the humid and flood-prone ecosystems of northeastern India. The short-duration rice cultivar Luit is widely cultivated in Assam because of its early maturity and adaptability; however, its susceptibility to BLB limits yield stability under disease-prone conditions. The present study aimed to improve BLB resistance in Luit through marker-assisted pyramiding of three major resistance genes, Xa21, xa13, and xa5. A marker-assisted backcross breeding approach was employed using IRBB60 as the donor parent. Gene-specific functional markers were used to track the target resistance genes, while polymorphic SSR markers were employed to assess recurrent parent genome recovery. Screening of the BC₂F₂ population identified 57 plants homozygous for all three resistance genes. The selected pyramided plants exhibited recurrent parent genome recovery ranging from 81.25% to 93.84% and retained the key agronomic characteristics of Luit, including early flowering, maturity duration, and grain yield. The resistance response of the pyramided plants was evaluated against three virulent Xoo isolates representing different agro-climatic regions of Assam. Plants carrying all three resistance genes consistently exhibited shorter lesion lengths than plants carrying one or two resistance genes and showed resistance levels comparable to those of the donor parent IRBB60. Several pyramided plants combined high levels of BLB resistance with high recurrent parent genome recovery and desirable agronomic performance. These findings demonstrate that marker-assisted pyramiding of Xa21, xa13, and xa5 is an effective strategy for improving BLB resistance in the genetic background of Luit. The selected pyramided materials provide valuable genetic resources for further evaluation and utilization in rice improvement programmes targeting BLB-prone environments.