Registration of TIL:383.13, TIL:625 and TIL:634, Three Long Grain Tropical Japonica Rice Germplasm Lines Containing Novel Indica Alleles that Increase Tiller Production and Grain Yield

Abstract

Three rice (Oryza sativa L.) germplasm lines designated TIL:383.13 (Reg. No. GP‐144, GSOR 100605), TIL:625 (Reg. No. GP‐145, GSOR 100698), and TIL:634 (Reg. No. GP‐146, GSOR 100702), contain a total of seven alleles of indica rice origin associated with earlier development and increased numbers of tillers during early plant development stages in an elite US tropical japonica rice genetic background having long grain shape and intermediate amylose content and gelatinization temperature. The three high‐tillering introgression lines also exhibit increased panicle number and grain yield and were jointly released in 2016 by the USDA‐ARS and Texas A&M Agrilife Research. The novel alleles for enhanced tiller production originated from ‘TeQing’, an indica rice cultivar from China, and were transferred through a series of backcrossing into lines having a predominantly ‘Lemont’ genetic background. TeQing is well known in the United States for both its high yield and its disease resistance but is not suitable for commercial production due to lodging and poor grain quality. A combination of molecular and phenotypic data was used to identify these three improved germplasm lines from among 123 TeQing‐into‐Lemont backcross introgression lines. A combination of phenotypic and molecular data was used to select three lines from among 123 TeQing‐into‐Lemont backcross introgression lines.

Mapping and Validation of Quantitative Trait Loci Associated with Tiller Production in Rice

“…While this increases breeder need for greenhouse and marker-assisted selection techniques, it also introduces uncertainty as to how well the QTLs and progeny selected under potted conditions will perform in transplanted or drill-seeded fields. Further evaluation of a subset of TILs selected for containment of the presently identified TN QTLs, sometimes alone but also in multi-QTL combinations, indicated that the TN QTLs reported here could indeed exert detectable differences in TN under drill-seeded field management systems (Pinson et al, 2015). The observed increases in early TN and canopy development did not, however, always translate into increased panicle number or grain yield (Pinson et al, 2015).…”

“…Because the segments of TeQing introgressed into each of the 123 TILs have been molecularly characterized, marker data can be used to identify specific TILs as donors of the desired TeQing TN QTLs into tropical japonica breeding programs. Pinson et al (2015) identified three TILs as potential donors for seven TN QTLs mapped in this study. Additional recombination generated among TIL cross progeny can also be used to fine-map and investigate allelism between these TN QTLs and the candidate genes identified from mutant loci.…”

“…Further evaluation of a subset of TILs selected for containment of the presently identified TN QTLs, sometimes alone but also in multi-QTL combinations, indicated that the TN QTLs reported here could indeed exert detectable differences in TN under drill-seeded field management systems (Pinson et al, 2015). While this increases breeder need for greenhouse and marker-assisted selection techniques, it also introduces uncertainty as to how well the QTLs and progeny selected under potted conditions will perform in transplanted or drill-seeded fields.…”

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

“…The lower TN characteristic of US tropical japonica rice cultivars has been attributed to a longer phyllochron (Morita et al, 2005) and is desired by some rice breeders for reducing the production of excessive, nonproductive tillers often seen in the indica cultivars grown throughout Asia (e.g., the New Plant Type [NPT] idiotype; Vergara et al, 1990; Khush, 2000; Sharma et al, 2013). Conversely, a series of studies comparing US tropical japonica rice germplasm with high‐yielding indica rice cultivars and several japonica × indica cross‐progeny suggested that an increase in TN would raise the yield potential of US rice cultivars (Samonte et al, 1998, 2001, 2006, 2010; Pinson et al, 2015a,b). The high‐yielding indica cultivar used in this series of studies was ‘TeQing’, whose yield advantage over US japonica cultivars in potted plant and drill‐seeded field‐plot studies was found associated with a complex of traits comprising rapid seedling development due to reduced seedling‐stage phyllochron, which allowed earlier tiller initiation from higher (rather than lower, or physiologically younger) main‐culm nodes, culminating in increased TN, PN, and grain yield.…”

“…The QTLs were identified using plant growth data collected from potted plants, leaving their value to field-grown plants uncertain. In subsequent evaluation of selected TILs in drill-seeded field plots, it was noted that some of the TeQing QTL combinations contained by the TILs proved to increase not just TN in the field but increased PN and grain yield as well (Pinson et al, 2015b). However, the greatest yield increases were observed in progeny lines that headed later than desired by most US rice breeding programs.…”