Molecular Breeding Of Root System Architectures For Improving Drought Resistance In Rice

Drought is the main abiotic stress hindering rice production under rain-fed conditions. To improve drought resistance in rice, molecular breeding for root system architecture using marker-assisted selection (MAS) is considered one of the most promising breeding strategies. We identified a deeper rooting quantitative trait locus (QTL), Dro1, using a map-based cloning strategy in mapping populations derived from a cross between IR64, a lowland rice with shallow roots, and Kinandang Patong (KP), an upland rice with deep roots. A near-isogenic line for Dro1 (Dro1-NIL) in the IR64 genetic background increased deep roots, resulting in drought resistance compared to IR64. To improve drought resistance in IR64, using MAS backcrossing, we introduced a chromosome segment of KP containing QTLs for root length (qRL6.1), root thickness (Sta1), and root volume (qFSR4) into IR64. Furthermore, using MAS pyramiding, we are in the process of developing IR64 with the KP alleles for Dro1, qRL6.1, Sta1, and qFSR4. We will evaluate the yield of these lines under drought conditions. To improve the root system architecture in other shallow-rooting varieties, we derived different F₂ populations from crosses between three different shallow-rooting varieties and KP, and analyzed the QTLs for deep rooting in these populations. We identified several QTLs for deep rooting. Currently, we are cloning of these QTLs and developing near-isogenic lines (NILs). These NILs will be promising materials for the future molecular breeding of root system architecture.