# The Molecular Breeding of Different Ecotype Japonica Varieties Resistant to Rice Blast with High Genome Collinearity

## TL;DR

Scientists developed japonica rice varieties with strong blast resistance, high yield, and good quality using molecular breeding techniques in the Yangtze River Delta region.

## Contribution

A novel approach combining molecular marker-assisted selection and GSR40K chip screening to improve blast resistance and adaptability in japonica rice.

## Key findings

- Introgression lines showed significantly enhanced blast resistance and higher yield compared to the recipient parent.
- Grain quality was improved synchronously with increased grain number per panicle.
- Two representative lines demonstrated good regional adaptability, blast resistance, and quality.

## Abstract

The Yangtze River Delta (YRD) is one of the most important japonica rice planting areas in China. Balancing the resistance, yield, and quality has always been a core issue in rice breeding due to the negative correlation among these three factors, while the broad-spectrum blast resistance gene Piz is closely linked with Hd1, the major gene regulating days to heading (DTH), and a precise combination of their beneficial alleles plays a key role in synchronously improving blast resistance and the regional adaptability of japonica rice in YRD. In this study, using the backcross progeny population derived from backbone parent ZD9471 and W1063, two alleles of Hd1 were identified. Then, through molecular marker-assisted selection combined with Green Super Rice 40K (GSR40K) chip-based screening, six introgression lines (ILs) with two different alleles combinations of Hd1 and Pigm were obtained. An evaluation of the blast resistance, yield, and quality traits showed that compared with the recipient parent, the panicle blast resistance of ILs was significantly enhanced; the grain number per panicle increased consistently with the delaying of the growth period, leading to higher yield in the ILs; the grain quality were synchronously improved. Two representative lines with similar genetic backgrounds but a significantly different regional adaptability, exhibiting a good blast resistance, high yield, and prominent quality were approved and demonstrated promising application prospects.