Given the impact of cold stress on rice productivity, tolerance to low temperatures is of considerable importance in temperate rice growing regions. In rice, efforts to improve cold tolerance typically focus on the seedling and reproductive stages of development. At the seedling stage, low temperatures can retard plant growth or lead to poor stand establishment, both of which negatively impact grain yield. One of our goals is to understand the molecular genetic basis of seedling cold tolerance in rice.

M202 is the predominant rice variety grown in California. Among its many positive attributes is good seedling cold tolerance. Previous genetic analysis of M202, a temperate japonica rice variety, has resulted in the identification of two major QTL, qCTS12 and qCTS4, which confer seedling cold tolerance to IR50, a cold sensitive indica variety developed in the Philippines. The effect of qCTS12 is observed under temperature conditions that result in wilting and necrosis in susceptible varieties while qCTS4 provides tolerance to conditions that cause chlorosis and stunting. We have recently fine mapped the qCTS12 locus and are currently working to develop a high resolution map of the qCTS4 locus.