Abstract
Straighthead, a physiological disorder characterized by sterile florets and distorted spikelets, causes significant yield losses in rice, and occurs in many countries. The current control method of draining paddies early in the season stresses plants, is costly, and wastes water. Development of resistant cultivar is regarded as the most efficient way for its control. We mapped a QTL for straighthead resistance using two recombinant inbred line (RIL) F9 populations that were phenotyped over two years using monosodium methanearsonate (MSMA) to induce the symptoms. One population of 170 RILs was genotyped with 136 SSRs and the other population of 91 RILs was genotyped with 159 SSRs. A major QTL qSH-8 was identified in an overlapping region in both populations, and explained 46% of total variation in one and 67% in another population for straighthead resistance. qSH-8 was fine mapped from 1.0 Mbp to 340 kb using 7 SSR markers and further mapped to 290 kb in a population between RM22573 and InDel 27 using 4 InDel markers. SSR AP3858-1 and InDel 11 were within the fine mapped region, and co-segregated with straighthead resistance in both RIL populations, as well as in a collection of diverse global accessions. These results demonstrate that AP3858-1 and InDel 11 can be used for marker-assisted selection (MAS) for straighthead resistant cultivars, which is especially important because there is no effective way to directly evaluate straighthead resistance.
Highlights
Straighthead is a physiological disorder in rice that is characterized by spikelet sterility resulting in blank panicles which remain upright at maturity
Straighthead segregated across the full rating range from 1 to 9 in both F9 recombinant inbred line (RIL) populations, which validated the effectiveness phenotyping of straighthead using monosodium methanearsonate (MSMA) (Fig. 2)
The evaluation has been conducted using arsenic-based herbicide MSMA which induces straighthead-like symptoms
Summary
Straighthead is a physiological disorder in rice that is characterized by spikelet sterility resulting in blank panicles which remain upright at maturity. Straighthead can result in almost complete loss of grain yield [1,2], and is occurring with increasing frequency in Arkansas where about 50% of USA rice is produced [3,4,5]. The D&D method is applied to more than one third of the rice acreage in Arkansas as a preventative measure and wastes some 150 million m3 of irrigation water each year [15]. Once straighthead occurs in a field, growers will keep using the D&D method because of unaffordable consequences. This method of straighthead prevention is costly and wasteful of natural resources, and results in drought-related yield loss
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