QTLs for Early Tiller Production and Relationships with Rapid Seedling Growth and Increased Panicle Number in Rice

Abstract

Tiller number (TN) is a key determinant of final grain yield in the small grains crops, including rice (Oryza sativa L.), and is desired to enhance competition with weeds. Quantitative trait loci (QTLs) associated with TN were mapped within a set of recombinant inbred lines developed from a cross between the low‐tillering tropical japonica cultivar ‘Kaybonnet‐lpa1‐1’ and the high‐tillering, high‐yielding, early‐maturing indica cultivar ‘Zhe733’ using data collected from greenhouse potted plants evaluated weekly. Relationships between the five identified TN QTLs and related traits including panicle number (PN), flag leaf number, seedling leaf number (SLN), and earliness of tiller production were also evaluated. The three TN QTLs that were linked with early tiller emergence were also associated with PN; two additional TN not associated with PN were also identified. All five TN QTLs were also SLN QTLs, though other loci affecting SLN were also identified. Several of the TN and SLN QTLs identified using data from young plants (e.g., ≤6 wk after planting) were not detectible in data collected just before or after heading. The three TN QTLs also associated with PN showed stronger effects (higher logarithm of the odds ratios and additive effects) on TN as observed in seedling stages than on final TN at heading time, and their effects diminished over time to the point that they were not always detectible in TN data collected at or after heading. However, the three TN QTLs that were also PN QTLs were robust enough that they were detected in the less intensive (one‐fourth the labor and resources) Arkansas trials, where tillers were counted from two single‐plant replications just twice, at 6 wk after planting and after heading. The three loci associated with both TN and PN are the TN loci most likely to increase rice yield, and the markers presently found linked to them can be used for marker assisted breeding.