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Wongsaprom C.,Kasetsart University | Sirithunya P.,Rajamangala University of Technology at Lanna | Vanavichit A.,Kasetsart University | Pantuwan G.,0 Paholyothin Rd. | And 4 more authors.
Field Crops Research | Year: 2010

Two quantitative trait loci (QTL) that confer a broad-spectrum resistance to blast disease identified in the rice cultivar Jao Hom Nin (JHN) were transferred to the Thai glutinous jasmine rice cultivar RD6 by marker-assisted backcrossing (MAB). Four backcrosses and one selfing were conducted in which the derived introgression lines (ILs) that carried homozygous JHN alleles at the QTL recovered up to 98% of the RD6 genome. Ninety-eight BC4F2 introgression lines that consisted of four combinations of the two QTL were evaluated for their resistance to eight single spore isolates and natural isolates at three research locations. Introgression lines were examined for their agronomic performance by comparing them to the original RD6 in multi-location trials across five locations. All ILs that carried the QTL (either one or two QTL) showed lower disease scores than ILs without any QTL and lower scores than the recipient cultivar RD6, whereas their agronomic performances were not significantly different from the original RD6. All ILs that carried at least one QTL showed a broad-spectrum blast resistance that was similar to the donor cultivar JHN. The success in improving the blast resistance in RD6 by MAB was shown. In this study, MAB accelerated the development of broad-spectrum blast resistance in the genetic background of the Thai glutinous rice cultivar RD6 within 4 years. The improved RD6 has now been tested in cultivation for several years. Two of the ILs were released in 2008. Currently, farmers in the north and northeast regions of Thailand (areas that are particularly vulnerable to blast disease) benefit from growing these two varieties. © 2010 Elsevier B.V.


Korinsak S.,Kasetsart University | Siangliw M.,Kasetsart University | Kotcharerk J.,Phitsanulok Rice Research Center | Jairin J.,Ubon Ratchathani Rice Research Center | And 5 more authors.
Field Crops Research | Year: 2016

Shifts in weather patterns and increases in the frequency and magnitude of extreme weather events resulting from unfavorable climate change have led to frequent flooding and brown planthopper outbreaks in rice fields, particularly those in rainfed lowland areas in Thailand. The traditional jasmine rice cultivar KDML105, which is popularly grown in rainfed lowland areas in north and northeast Thailand, is intolerant to flash flooding and is very susceptible to the brown planthopper. Two major QTL, Sub1 and Qbph12, were individually introgressed from two donors into KDML105 using the marker-assisted backcrossing method. In this study, we have pyramided Sub1 and Qbph12 in the genetic background of KDML105 via marker-assisted selection coupled with stringent phenotypic selection for plant type and physical grain quality traits. In total, sixty-four pyramid lines (PLs) were developed and characterized for submergence tolerance, brown planthopper resistance, important agronomic traits and physical and chemical grain quality. Evaluation of the PLs indicated their significantly enhanced submergence tolerance and brown planthopper resistance compared with the original KDML105 line. All PLs satisfied the KDML105 grain and cooking quality standards, although their agronomic characteristics showed significant variations in days to flowering, plant height and grain yield. These variations might allow breeders to select new versions of KDML105 that are suitable for different locations in rainfed lowland environments. © 2015 Elsevier B.V..


Win K.M.,Kasetsart University | Korinsak S.,Kasetsart University | Jantaboon J.,Kasetsart University | Siangliw M.,Kasetsart University | And 7 more authors.
Field Crops Research | Year: 2012

Bacterial blight (BB) caused by Xanthomonas oryzae pv. oryzae is one of the most devastating diseases of rainfed lowland rice in Thailand. The gene Xa21 shows broad-spectrum resistance and has been widely utilized to improve BB resistance in rice worldwide. However, Xa21 is not fully expressed in the early stages of development (seedling stage). In this study, we attempted to improve the Thai jasmine rice variety KDML105 to obtain non-age-related broad-spectrum resistance to BB. The Xa21 gene and seedling resistance genes from rice variety IR1188 (a variety with non-age-related broad-spectrum resistance to BB) were introgressed into KDML105 through three rounds of marker-assisted backcrossing (MAB) and phenotypic selection. Sixty KDML105 backcross introgression lines (KBILs) carrying the Xa21 gene were successfully developed. They were used to evaluate seedling resistance against thirteen Xoo strains. Three seedling resistance (SR) loci inherited from IR1188 were identified on rice chromosomes 1 (RM302-RM212), 8 (RM210-RM149) and 11 (RM287-RM224). The agronomic characters of the KBILs were assessed by planting these lines in the paddy field at Kasetsart University in 2003. Phenotypic variation was observed in the agronomic traits of these lines. Seven KBILs carrying the Xa21 and multiple SR loci and also having a similar plant type to the original KDML105 were chosen for testing in multi-location trials at research stations in rainfed lowland environments. The trials were conducted in 10 and 11 locations in the North and Northeast of Thailand, respectively, between 2005 and 2006. The yield, agronomic traits, cooking quality and important diseases were examined and compared with those of the original KML105. All of the 7 KBILs had a cooking quality profile (aroma, amylose content, gel consistency and alkaline spreading value) and agronomic performance similar to the original KDML105. In 2007, four KBILs were planted in farmers' fields at 5 locations. All BILs and the original KDML105 did not differ significantly in their agronomic performance. In this study, multiple loci for broad-spectrum seedling resistance were identified from the KBIL population developed by the integrated marker-assisted and phenotypic selection procedures (MAS and PS). These results facilitated the successful improvement of non-age-related broad-spectrum BB resistance in KDML105. The established non-age-related broad-spectrum BB-resistant KDML105 is currently recommended by Kasetsart University for planting in farmers' fields where the crop is vulnerable to BB. © 2012 Elsevier B.V.


Shrestha B.K.,Louisiana State University | Shrestha B.K.,University of Florida | Karki H.S.,Louisiana State University | Karki H.S.,Norwich Research Park | And 3 more authors.
PLoS ONE | Year: 2016

Potential biological control agents for two major rice diseases, sheath blight and bacterial panicle blight, were isolated from rice plants in this study. Rice-associated bacteria (RABs) isolated from rice plants grown in the field were tested for their antagonistic activities against the rice pathogens, Rhizoctonia solani and Burkholderia glumae, which cause sheath blight and bacterial panicle blight, respectively. Twenty-nine RABs were initially screened based on their antagonistic activities against both R. solani and B. glumae. In follow-up retests, 26 RABs of the 29 RABs were confirmed to have antimicrobial activities, but the rest three RABs did not reproduce any observable antagonistic activity against R. solani or B. glumae. According to16S rDNA sequence identity, 12 of the 26 antagonistic RABs were closest to Bacillus amyloliquefaciens, while seven RABs were to B. methylotrophicus and B, subtilis, respectively. The 16S rDNA sequences of the three non-antagonistic RABs were closest to Lysinibacillus sphaericus (RAB1 and RAB12) and Lysinibacillus macroides (RAB5). The five selected RABs showing highest antimicrobial activities (RAB6, RAB9, RAB16, RAB17S, and RAB18) were closest to B. amyloliquefaciens in DNA sequence of 16S rDNA and gyrB, but to B. subtilis in that of recA. These RABs were observed to inhibit the sclerotial germination of R. solani on potato dextrose agar and the lesion development on detached rice leaves by artificial inoculation of R. solani. These antagonistic RABs also significantly suppressed the disease development of sheath blight and bacterial panicle blight in a field condition, suggesting that they can be potential biological control agents for these rice diseases. However, these antagonistic RABs showed diminished disease suppression activities in the repeated field trial conducted in the following year probably due to their reduced antagonistic activities to the pathogens during the long-term storage in -70C, suggesting that development of proper storage methods to maintain antagonistic activity is as crucial as identification of new biological control agents. © 2016 Shrestha et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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