Abstract
To develop superior rice varieties with improved yield in most rainfed areas of Asia/Africa, we started an introgression-breeding program for simultaneously improving yield and tolerances of multiple abiotic stresses. Using eight BC1 populations derived from a widely adaptable recipient and eight donors plus three rounds of phenotypic selection, we developed 496 introgression lines (ILs) with significantly higher yield under drought, salt and/or non-stress conditions in 5 years. Six new varieties were released in the Philippines and Pakistan and many more are being evaluated in multi-location yield trials for releasing in several countries. Marker-facilitated genetic characterization revealed three interesting aspects of the breeding procedure: (1) the donor introgression pattern in specific BC populations was characteristic; (2) introgression frequency in different genomic regions varied considerably, resulting primarily from strong selection for the target traits; and (3) significantly lower heterozygosity was observed in BC progenies selected for drought and salinity tolerance. Applying strong phenotypic selection under abiotic stresses in early segregating generations has major advantages for not only improving multiple abiotic stress tolerance but also achieving quicker homozygosity in early generations. This breeding procedure can be easily adopted by small breeding programs in developing countries to develop high-yielding varieties tolerant of abiotic stresses. The large set of trait-specific ILs can be used for genetic mapping of genes/QTL that affect target and non-target traits and for efficient varietal development by designed QTL pyramiding and genomics-based recurrent selection in our Green Super Rice breeding technology.
Highlights
As the most important human staple food, approximately 90% of rice is grown and consumed in Asia
We reported a modified BC breeding procedure for improving multiple complex traits, which resulted in the release and up-scaling of four new rice varieties for rainfed areas of the Philippines with superior yield potential and good tolerance of drought and salinity, two new varieties for the irrigated areas of Pakistan, plus many promising ones in the pipeline to be released from only eight BC populations in 6 years
We found that more promising introgression lines (ILs) were selected from populations HHZ5 (OM1723) and HHZ17 (CDR22) than others, indicating that donors did make differences in breeding efficiency, when defined as the number of new varieties and promising lines developed per breeding population, and OM1723 and CDR22 have favorable alleles for the target traits at more loci complementary to HHZ
Summary
As the most important human staple food, approximately 90% of rice is grown and consumed in Asia. Over the past few decades, irrigated rice has been the research focus for enhancing rice productivity by increasing inputs in many Asian countries. Rice production in the subtropical regions of western China, Pakistan and northwest India depends largely on supplementary irrigation in the wet seasons. Dry-season irrigated rice areas are mostly concentrated in southern and central China, southern and eastern India and the whole of Southeast Asia, where has recently had a lack of irrigation water at critical crop growth stages in many of these irrigated rice areas. Many countries will be suffering from physical water scarcity by 2025, especially in the wet-season irrigated areas in northern China (2.5 mha), Pakistan (2.1 mha) and northern and central India (8.4 mha) [1]. The complexity of abiotic stresses increases multifold as we move to rainfed areas, which have received much less research investment with fewer research products to test
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
