Marker-Assisted Development and Evaluation of Monogenic Lines of Rice cv. Kaohsiung 145 Carrying Blast Resistance Genes

Abstract

Rice blast is a serious threat to global rice production. Large-scale and long-term cultivation of rice varieties with a single blast resistance gene usually leads to breakdown of resistance. To effectively control rice blast in Taiwan, marker-assisted backcrossing was conducted to develop monogenic lines carrying different blast resistance genes in the genetic background of an elite japonica rice cultivar, ‘Kaohsiung 145’ (KH145). Eleven International Rice Research Institute (IRRI)-bred blast-resistant lines (IRBLs) showing broad-spectrum resistance to local Pyricularia oryzae isolates were used as resistance donors. Sequencing analysis revealed that the recurrent parent, KH145, does not carry known resistance alleles at the target Pi2/9, Pik, Pita, and Ptr loci. For each IRBL x KH145 cross, we screened 21–370 (average of 108) plants per generation from the BC1F1 to BC3F1/BC4F1 generation. A total of 1499 BC3F2/BC4F2 lines carrying homozygous resistance alleles were selected and self-crossed for 4–6 successive generations. The derived lines were also evaluated for background genotype using genotyping by sequencing, for blast resistance under artificial inoculation and natural infection conditions, and for agronomic performance in multiple field trials. In Chiayi and Taitung blast nurseries in 2018–2020, Pi2, Pi9, and Ptr conferred high resistance, Pi20 and Pik-h moderate resistance, and Pi1, Pi7, Pik-p, and Pik susceptibility to leaf blast; only Pi2, Pi9, and Ptr conferred effective resistance against panicle blast. The monogenic lines showed similar agronomic traits, yield, and grain quality as KH145, suggesting the potential of growing a mixture of lines to achieve durable resistance in the field.

Marker-Assisted Pyramiding of Blast-Resistance Genes in a japonica Elite Rice Cultivar through Forward and Background Selection

“…The ascertainment of the effect of pyramiding on resistance durability would require the long-term monitoring of field resistance for the pyramided lines. However, reports of increased resistance (i.e., fewer lesions) provided by stacking different blast- R genes are available: rice pyramiding of Pi1 + Piz-5 + Pita2 and Pi-1 + Pi-9 + Pi-kh enhanced blast resistance in comparison to a single gene [ 53 , 54 , 55 ]; nine Pi genes were introgressed individually or in combination of two by MABC, and the obtained lines demonstrated that Pigm and Pid3 significantly enhanced resistance during the growth period [ 56 ]; Wu et al [ 57 ] obtained pyramided lines carrying different alleles of the Piz locus ( Pigm , Pi40 , Pi9 , Pi2 , and Piz ) combined with Pi1 , Pi33 , and Pi54 , respectively, and demonstrated that polygene pyramided lines displayed more seedling and panicle blast resistance than monogenic lines.…”

Molecular Breeding of Zheyou810, an Indica–Japonica Hybrid Rice Variety with Superior Quality and High Yield

“…The lines were found to carry the S5-n gene and exhibit higher seed-setting rates than the control japonica restorer line, indicating the potential for improved fertility in indica-japonica hybrids [32]. Furthermore, the broad-compatibility gene S5-n has been introduced into the maintainer line Zhen5B and the restorer line SIR2622 using molecular marker-assisted breeding, resulting in significant improvements in the fertility of indica-japonica hybrids [36]. Based on the research conducted, it is evident that the introduction of the S5-n molecular marker into restorer lines improves the hybrid vigor of the indica-japonica hybrid F 1 .…”

“…For instance, Liu et al utilized PCR-AccI molecular markers to introduce Wx b into the indica hybrid rice parents Longtefu and Zhenshan97 [11]. Similarly, Chen used molecular marker-assisted selection to obtain a high-quality early indica rice line Ganzaoyou57, which exhibited both high yields and low amylose content [36]. Also, the Wx b gene was inserted into Teqing and Xieyou 57, leading to significant improvements in cooking and eating qualities [11,40].…”