Rice yield reductions from drought in rainfed areas range from 20 to 100%. Similarly, salt stress is the second most important abiotic stress limiting rice productivity, particularly in coastal areas and some inland rice fields. It is estimated that 20–50% of the irrigated rice lands are somewhat salt-affected [9]. Frequently, drought goes hand in hand with salinity in many areas of Asia where irrigation is used to reduce soil salt in rice paddy fields. For instance, reduced fresh water in irrigation often induces secondary salinization and aggravates the effects of salinity. Alternatively, secondary salinization worsens the effects of drought on rice. To achieve

high yield (HY) and yield stability through breeding, breeders have to develop high yielding rice varieties with significantly improved tolerances MDV3100 to drought and salinity. Challenges then arise from the fact that HY, drought tolerance (DT) and salt tolerance (ST) are all complex traits controlled by polygenes, possible negative associations of rice DT or ST with HY, and different genetic and physiological mechanisms of the same traits at different developmental stages [10], [11] and [12]. Everolimus molecular weight In addition,

selection of the right parental lines as donors for target traits has been difficult in real breeding programs. For instance, many rice landraces have good levels of DT and ST, but are low yielding [11]. Genetic drag is another major concern to breeders when they are making decisions in choosing landraces as trait

donors, particularly when the conventional pedigree breeding method is used [13]. While commonly used to improve single highly heritable traits, backcross (BC) breeding and strong phenotypic selection have been proven to be effective for improving single complex traits, particularly abiotic stress tolerances in rice [14], [15] and [16]. However, when aiming at improving multiple complex traits using phenotypic selection in a real BC breeding program, breeders are facing several important and tricky issues regarding what selection strategy should be used. This is particularly true when breeders have to deal with trait selection in two contrasting environments — the normal summer selleck screening library crop season(s) in the target environments (TEs) and short-day winter nurseries of the tropical climate in Hainan, in order to speed up the breeding process. Thus, it remains unclear to most breeders as to what traits or trait combinations should be selected in each of the breeding environments. In particular, in what order and what environments, should different target traits be selected to achieve the best overall genetic gain within the shortest time, when multiple complex target traits have to be improved. In this study, we tried to answer these questions by presenting results from an effort for simultaneously improving HY, DT and ST of rice using introgression breeding.