Location: Dale Bumpers National Rice Research CenterTitle: Field evaluation of potential weed-suppressive traits in an indica x tropical japonica mapping population
|ZHANG, FANTAO - Jiangxi Normal University|
Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/25/2016
Publication Date: 7/2/2017
Citation: Gealy, D.R., Pinson, S.R., Jia, Y., Zhang, F. 2017. Field evaluation of potential weed-suppressive traits in an indica x tropical japonica mapping population. 36th Rice Technical Working Group Meeting Proceedings, Galveston, TX. p. 106. March 1-4, 2016. CDROM.
Technical Abstract: The indica rice accession, PI 312777 (a.k.a. WC 4644), is highly productive and can suppress barnyardgrass (Echinochloa crus-galli) in reduced-input systems, but the genetic control of this weed suppression is unknown. A set of 330 recombinant inbred lines (RILs) was developed using single seed descent from a cross between ‘Katy’ (non-weed-suppressive tropical japonica [TRJ]) and PI 312777 (weed-suppressive, allelopathic) for the purpose of identifying the genetic bases of weed suppression. The objective of this study was to evaluate potential weed suppressive traits with which to select a subset of F8 RILs exhibiting extreme contrasting phenotypes for further evaluation in field, greenhouse, and laboratory experiments, to identify QTLs for these traits, and to further evaluate the role of each gene and trait in weed-suppression and allelochemical exudation. At Stuttgart, AR in 2015, three replicate plots each of 330 RILs (F8 seed) were drill-seeded at a rate of ~320-330 seeds/plot in 2.13 m long plots consisting of two rows 30.5 cm apart. Nitrogen fertilizer was broadcast at a rate of 110 kg ha-1 as urea before application of the permanent flood, and plots were maintained weedfree using commercially available herbicides and hand-weeding. Transgressive variation was observed among most phenotypic traits, many of which have been shown to be associated with weed suppression. These included leaf area development, seedling growth rate, plant height, tiller number, and grain yield. Leaf area per plant (estimated as total leaf number per plant x average length of 5 leaves x average width of 5 leaves at the midpoint) at 3 weeks after emergence (WAE) ranged from 3 to 221 cm2, averaging 73 cm2, compared with 79 and 55 cm2 for the indica and TRJ parents, respectively. Seedling growth rate from emergence to 2 weeks after permanent flood (WAF) ranged from 0.9 to 2 cm/day, averaging 1.4 cm/day, which was the same as both parents. At 2 WAF plant heights ranged from 35 to 85 cm, averaging 56 cm, compared with 56 and 57 cm for the indica and TRJ parents, respectively. Plant growth rate from 2 WAF to maturity ranged from .27 to 3 cm/day, averaging 1.1 cm/day, compared with 0.9 and 1.2 cm/day for the indica and TRJ parents, respectively. Tiller number at 2 WAF ranged from a rating of 1 to 6, (based on a relative scale in which the indica parent was defined as 5 and the TRJ parent was defined as 1) averaging ~3. Days to heading ranged from 58 to 130 days after emergence (DAE), averaging 86 DAE, compared with 85 DAE for both parents. Mature plant heights ranged from 62 to 164 cm, averaging 109 cm, compared with 101 and 115 cm for the indica and TRJ parents, respectively. Grain yields ranged from to 2160 kg/ha to 11000 kg/ha, compared with ~11030 kg/ha and 8390 Kg/ha for the indica and TRJ parents, respectively. A replicated greenhouse study was conducted with F9 plants to evaluate tiller and panicle development over time. Tiller number at 5 WAP ranged from 1.8 to 5.0 tillers/plant, averaging 3.2, compared with 4.1 and 2.9 tillers/plant for the indica and TRJ parents, respectively. Panicle number at maturity ranged from 1.9 to 8.0 panicles/plant, averaging 3.2, compared with 4.3 and 2.6 panicles/plant for the indica and TRJ parents, respectively. Panicle number was moderately correlated with tiller number at 5 WAP (r=0.44) and more highly correlated with tiller number at 11 WAP (r=0.72) Overall, several RILs were taller, had greater growth rates, and produced more leaf area than either parent, suggesting that they might be well-suited for weed suppression, however few RILs consistently produced more tillers or yield than the indica parent in the field. A subset of these RILs, based on contrasting phenotypes, is being selected for mapping studies. These results will be used to identify rice genotypes that optimize both weed suppression and crop produ