CULTIVAR

‘Rondo’, a Long-Grain Indica with Resistances to Multiple Diseases

WenGui Yan* and Anna M. McClung

ABSTRACT Indica rice (Oryza sativa L.) is needed to increase the genetic diversity in future U.S. cultivars. Furthermore, resistant germplasm is needed to control newly occurring races of blast disease [Magnaporthe grisea (Hebert) Barr]. ‘Rondo’ rice (Reg. No. CV-131, PI 657830) is a long-grain cultivar meeting these needs and was developed by the USDA-ARS through mutation breeding from a Chinese indica germplasm ‘4484’ (PI 615022). Rondo’s indica origin is genetically distant from U.S. cultivars. Rondo is resistant to all major races of blast disease currently identifi ed in the USA, including two newly reported races, TM2 and IB33, and fi ve other rice diseases. Among seven known resistance genes for blast, only Pi-b has been identifi ed in Rondo, indicating that it may possess novel blast resistance genes. The Uniform Regional Rice Nursery (URRN) conducted jointly in fi ve southern rice-producing states demonstrated that Rondo yields similarly to ‘Francis’, ‘Wells’, and ‘Cocodrie’, high yielding cultivars in the mid-south USA. Cereal quality analyses indicated that Rondo has the same parboiling, processing, and canning qualities as ‘Dixiebelle’ and ‘Sabine’, which have been accepted by the processing industry. Additionally, it can be used as conventional long-grain rice. Although the head rice yield appears at times to be lower than other long-grain cultivars, this should be less of a concern when it is parboiled. In conclusion, Rondo is a long-gain indica cultivar with high yield potential, an excellent disease resistance package, and premium processing quality. Rondo has been entered in the U.S. germplasm collection and is available for commercial purposes through the Research Improvement Association.

HE U.S. rice breeding programs have focused on two major ability to pest attack which could seriously jeopardize sus- Tgrain types, medium (or short) and long (Mackill and tainable crop production (Qualset and Shands, 2005). Thus, McKenzie, 2003). The former is mainly grown in a cultivar with a different genetic background is needed to and the latter in the mid-south rice belt including , diversify the gene pool of U.S. rice cultivars. , , , and Texas. The long-grain Rice blast disease is one of the most damaging and type belongs to tropical japonica and the medium (or short) prevalent diseases worldwide (Zeigler et al., 1994) as well to temperate japonica, two groups of the japonica subspecies as in the southern rice producing states (Moldenhauer et in Oryza sativa (Mackill, 1995). Another subspecies, indica, al., 1992). Application of fungicides and use of resistance has greater genetic diversity than japonica (Gao et al., 2005; cultivars are major means of controlling this economi- Mackill, 1995; Negrao et al., 2008; Caicedo et al., 2007; Kon- cally important disease. For example, in 2004, fungicides ishi et al., 2008). Furthermore, intensive breeding efforts were applied on more than 243,000 hectares of rice or have greatly reduced the genetic diversity among U.S. rice approximately 39% of the crop in Arkansas (Cartwright et cultivars (Dilday, 1990). For example, pedigree analysis dem- al., 2005). Planting resistance cultivars containing major onstrates that rice cultivars can be traced back to 22 germ- resistance genes that inhibit infection of one or more spe- plasm accessions in the southern rice belt and 23 accessions cifi c blast fungal biotypes or races common in rice fi elds is in California (Dilday, 1990; Bockelman et al., 2003). Narrow a primary blast-control strategy. When the Pi-ta gene was genetic diversity in a crop is often associated with its vulner- fi rst deployed with the release of cultivar ‘Katy’ in 1989, it conferred resistance to all blast races found in the USA (Jia et al., 2002). However, because of the pathogen’s inher- ent ability to adapt and overcome major resistance genes in USDA-ARS, Dale Bumpers National Rice Research Center, 2890 plants, it is a constant endeavor to maintain adequate crop Hwy. 130 East, Stuttgart, AR 72160. Registration by CSSA. Received 24 July 2009. *Corresponding author ([email protected]). disease resistance. For example, the resistance conveyed by the Pi-ta has been overcome by the newly identifi ed races Published in the Journal of Plant Registrations 4:131–136 (2010). TM2 in the fi eld and IB33 in the laboratory. In 2004, a doi: 10.3198/jpr2009.07.0404crc newly released cultivar ‘Banks’, containing the Pi-ta gene, © Crop Science Society of America incurred severe blast damage in several Arkansas locations 5585 Guilford Rd., Madison, WI 53711 USA (Lee et al., 2005). This highlights the constant challenge All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, faced by breeders to pyramid new resistance genes to main- recording, or any information storage and retrieval system, without permission in tain production stability (McClung et al., 2006). Thus, new writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.

Journal of Plant Registrations, Vol 4, No. 2, May 2010 131 sources of germplasm resistant to the shifting mix of blast mont, TX. Also, molecular markers for genes conveying races are urgently needed. resistance to various races of blast pathogen were assessed ‘Rondo’ rice is a long-grain cultivar that has been released in the RRU. Multiple diseases were evaluated in tests with to address these needs. Rondo belongs to indica rice subspe- four replications (single row plot; 1.8 m long and 0.3 m cies and is resistant or very resistant (rating 0–3 on a 0-to-9 wide) arranged in a randomized complete block design scale) to all major blast disease races currently identifi ed in (RCBD) at the Rice Research Station, Louisiana State Uni- the USA, including TM2 and IB33, as well as to fi ve other versity, Crowley, LA. A mixture of pathogen isolates as inoc- rice diseases. Rondo yields similarly to Francis, Wells, and ulum for sheath blight (Rhizoctonia solani Kühn) (Wamishe Cocodrie, high-yielding cultivars in the mid-south rice belt. et al., 2007), blast, and bacterial panicle blight [Burkholderia Its processing qualities are similar to those for Dixiebelle and glumae (Kurita and Tabei, 1967) Urakami et al. 1994] (Groth Sabine, which are well accepted by the processing industry. et al., 2007) was applied to each plot. Evaluation of nar- row brown leaf spot [Cercospora janseana (Racib) O. Const.] Methods (Webster and Gunnell, 1992) was conducted under natu- Rondo was developed by mutation breeding from 4484, rally infestation conditions. Lab evaluations for the com- an accession (http://www.ars-grin.gov/cgi-bin/npgs/acc/ mon races of blast pathogen were conducted in Pathology display.pl?1538931; verifi ed 8 February 2010) introduced in Department, University of Arkansas (UA), Fayetteville, AR, 1996 through a U.S–China germplasm exchange program. Ini- in 2006 and 2007, and at the Rice Research and Extension tial fi eld evaluations of 4484 at Stuttgart, AR, demonstrated its Center (RREC), UA, Stuttgart, AR, in 2008. Inoculum of excellent grain-yield potential and good milling quality. How- each blast race was applied to plots replicated three times ever, it is relatively tall, susceptible to lodging, and its amylose and arranged in the RCBD. Straighthead, a physiological content was too low for the U.S. long-grain market. disorder, was evaluated by means of application of arsenic Approximately 10,000 dry seeds of 4484 were irradiated in form of monosodium methanearsonate (MSMA) to soil with γ rays generated from Cs-137 inside a γ cell 1000 at 300 described by Yan et al. (2005) at the RREC. Gy by Florida Accelerator Services and Technology, Gaines- Meanwhile, 4484-1693 was included in the statewide ville, FL, in 2001. The M1 generation from the treated seeds Arkansas Disease Monitoring Program (ADMP) of 30 on- was grown at Stuttgart, AR. The selected panicles of the M2 farm county trials; 17, 7, and 6 counties in 2006, 2007, and with fairly good seed set were grown in the Lajas, Puerto 2008, respectively. Grain yield and disease reaction were

Rico, winter nursery. The selected panicles of the M3 were evaluated in tests having four replications arranged in the planted in single hill plots at Stuttgart in 2002 and selected RCBD. Narrow brown leaf spot, kernel smut [Neovossia hor- panicles of the M4 were evaluated for agronomic perfor- rid (Takah.) Padwick & A. Khan] and leaf smut (Entyloma mances at Stuttgart in 2003. One panicle row of the M5, oryzae Syd. & P. Syd.) (Brooks et al., 2009), sheath blight, 1047, had a shorter plant height than its parent 4484 and bacterial panicle blight, black sheath rot [Gaeumannomyces in 2004 this selection was assigned entry 1693 in a prelimi- graminis (Sacc.) Arx & D. Olivier var. graminis] (Webster and nary yield test. The yield test was performed at Stuttgart in Gunnell, 1992), stem rot (Sclerotium oryzae Catt) (Webster a plot size of 4.5 × 1.8 m with a total of four replications. In and Gunnell, 1992), and false smut [Ustilaginoidea virens this trial, the entry 4484-1693 was 10 cm shorter and the (Cke.) Tak] (Brooks et al., 2009) were rated in timely man- amylose content was 4% (w/w) higher than 4484. A second ner for each cultivar by a 0-to-9 scale where 0 was immune year fi eld evaluation was conducted to verify plant heights and 9 was completely infested. and amylose content. Meanwhile, 4484-1693 was tested in In 2008, 4484-1693 was included in on-farm evaluation the Arkansas Rice Preliminary Test (ARPT). programs for new cultivars in replicated tests of four mid- Analysis of individual plants of 4484 revealed that het- south states: studies with six rates of nitrogen fertilizer and erogeneity for amylose content was responsible for the three planting dates at three Arkansas locations, state-wide higher content in the selection of 4484-1693. In 2005, 4484, trials in six Mississippi counties, two planting dates at two and 4484-1693 were planted in 800 single-plant-hill plots, Texas locations, fi eld trials in six Louisiana parishes, and and 50 plants were harvested and analyzed for apparent two seeding methods (water-seeded and drill-seeded) at amylose content and waxy gene alleles. There were three two planting dates (16 April and 6 May) in Missouri. waxy alleles in 4484, high amylose allele of 107 bp in 50% Data from these tests were analyzed by the GLIMMIX of plants, low amylose allele of 122 bp in 37%, and inter- procedure in SAS version 9.1.3, where the cultivar was mediate amylose allele of 126 bp in the remaining 13%. All treated as a fi xed effect, while year, state, and their interac- plants of 4484-1693 had the high amylose allele of 107 bp. tions were treated as random effects. From 2006 to 2008, 4484-1693 was entry 75 (or RU0603075) in the Uniform Regional Rice Nursery (URRN) Characteristics described by Yingling et al. (2008). Tests for grain yield, milling yield, maturity, and plant height were conducted Agronomic and Botanical Description jointly in Texas, Louisiana, Arkansas, Missouri, and Missis- Rondo possesses a semidwarf-plant type which is 10 cm sippi in fi eld trials having 3.1- × 1.8-m plots and three repli- shorter than its parent 4484. Its height is similar to Fran- cates. Parameters measuring cooking quality and molecular cis and Wells, two long-grain cultivars that covered 47% markers for genes controlling cooking quality were ana- of Arkansas rice area in 2007 (Wilson and Runsick, 2008), lyzed in the USDA-ARS Rice Research Unit (RRU), Beau- and about 8 cm taller than Cocodrie (Table 1), another long-

132 CULTIVAR Journal of Plant Registrations, Vol. 4, No. 2, May 2010 grain cultivar grown in the mid-South rice states (Anony- Disease Reactions mous, 2008). All plant parts are pubescent. In 45 mid-South Accession 4484 is resistant to seven races of blast patho- regional trials, the average days from emergence to 50% gen (Eizenga et al., 2006). As expected, numerous fi eld and heading were 92, about 8 d later than Francis and Dixiebelle lab evaluations conducted in Arkansas, Louisiana, and Texas (McClung et al., 1998). At maturity, the spikelet is straw-col- including the URRN, ADMP, and ARPT demonstrated that ored and awnless or has a few short awns. At heading, the Rondo is resistant or very resistant (rating 0–3 on a 0-to-9 apiculus is green and then fades to straw color by maturity. scale) to the 11 races of blast disease currently identifi ed in The fl ag leaf remains green and stays erect at maturity. the mid-South states including TM2 and IB33 (Table 2 and 3) (Boza et al., 2007). Molecular marker analyses have shown Genetic Background that Rondo, like 4484, possesses only one major gene for Accession 4484 (PI 615022) from which Rondo is derived blast resistance, Pi-b, among seven known Pi genes (-ta, -b, belongs to indica subspecies according to the description -z, -kh, -ks, -d, and –i) existing in the mid-South rice cultivars from its provider. Analysis of genetic diversity and genetic (Table 3) (Eizenga et al., 2006; Fjellstrom et al., 2004). Since distance confi rmed its indica origin, which is genetically dis- Pi-b does not confer resistance to two of the races, IB33 and tant from all U.S. cultivars of tropical japonica origin (Agrama IB49 (Fjellstrom et al., 2004), to which Rondo is resistant, this and Eizenga, 2008). A genetically distant relationship is usu- cultivar appears to have a resistance gene(s) other than the ally responsible for plant sterility in the F1 generation, which Pi-b. This resistance gene is new because it has not been previ- has been frequently observed in the crosses of Rondo with ously reported in mid-South cultivars or may be new globally U.S. cultivars. Indica rice is less tolerant than japonica to cold because such report has not been observed so far. Therefore, temperature. Therefore, Rondo should not be seeded too Rondo can serve as an important resource of novel resistance early in the season but not too late as well because it heads for pyramiding genes to control blast disease in U.S. cultivars. about 1 wk later than Francis and Dixiebelle. In addition, fi eld evaluations have shown that Rondo is resistant or very resistant to narrow brown leaf spot (rat- Yield Performance ing 1–3 on a 0-to-9 scale), fairly resistant to kernel smut In 67 statewide and regional tests conducted across the and leaf smut, moderately resistant (3–4) to sheath blight, mid-South USA (Arkansas, Texas, Louisiana, Mississippi, resistant or moderately resistant (3–4) to bacterial panicle and Missouri) during 2004 through 2008, the average blight, moderately resistant or moderately susceptible (2–5) grain yield of Rondo was 9297 versus 8736 kg ha−1 for Fran- to black sheath rot, moderately susceptible (rating 2–3 on a cis, 8693 kg ha−1 for Wells, and 8753 kg ha−1 for Cocodrie. 1-to-5 scale) to stem rot, and susceptible or very susceptible Results of the URRN from 2006 to 2008 demonstrated to both false smut and straighthead (Table 2). that Rondo yielded similarly to Francis, Wells, and Coc- odrie and higher than Priscilla, Saber, and Presidio (Table Cooking Quality 1), indicating that Rondo is well adapted across the mid- Although Rondo can be used by the milling industry South rice growing states. Grain yield of Rondo was ranked as are other conventional long-grain cultivars, it also pos- twenty-fi rst among 200 entries in 2008 URRN. Occasion- sesses superior processing quality (parboiling and canning) ally, Rondo is more susceptible to lodging than some of the similar to Dixiebelle (McClung et al., 1998), ‘Bowman’, and U.S. cultivars, especially when heavily fertilized with nitro- Sabine, which should make it well accepted by the process- gen. Statewide variety × nitrogen tests in Arkansas in 2008 ing industry. The superior processing quality of Rondo is concluded that the optimum rate of nitrogen for Rondo is associated with the presence of the CT11 (105 nt) allele of about 80% of the rate for conventional U.S. cultivars. the Waxy gene as identifi ed by the RM190 microsatellite marker on chromosome 6 (Table 2). This allele is associated Milling Quality with high hot paste and cool paste viscosities as measured In 39 statewide and regional tests conducted across by the Rapid Visco Analyzer (RVA). Parboiled-milled Rondo the mid-South states (Arkansas, Texas, Louisiana, Missis- has the same RVA peak viscosity and shear as Dixiebelle sippi, and Missouri) during 2004 through 2008, the aver- and Sabine but higher RVA peak and fi rmer shear than age milling yield of Rondo was 51% of head and 68% of Wells. The endosperm of Rondo is nonglutinous, nonaro- total rice versus 56% of head and 69% of total for Francis, matic, and is covered by a light brown pericarp. 55% of head and 70% of total for Wells, and 58% of head and 70% of total for Cocodrie, respectively. This indicates Seed Availability that Rondo has slightly less head-rice yield than current Release certifi cation of the Rondo cultivar was granted by commercial cultivars (Table 1). However, the lower head the Texas State Seed and Plant Board on 10 June 2009. Seed rice yield is less of a concern when rice is parboiled. The of Rondo was deposited in the National Plant Germplasm test weight of Rondo (490 g/L or 38 lbs/bu) is slightly lower System (http://www.ars-grin.gov/npgs/index.html; verifi ed 7 than that of Francis (541 g/L or 42 lb/bu), Wells (554 g/L or February 2010), and maintained by the National Small Grains 43 lb/bu), Sabine (554 g/L or 43 lb/bu), and Cocodrie (528 Collection, Aberdeen, ID (http://www.ars-grin.gov/cgi-bin/ g/L or 41 lb/bu) because of its pubescent grains. The kernel npgs/html/site.pl?NSGC; verifi ed 7 February 2010) where it is weight and grain dimensions of Rondo are similar to Wells publicly available for research purposes. It is requested that and Francis but greater than Sabine and Dixiebelle. appropriate recognition of the germplasm source be given when this cultivar contributes to research and development

Journal of Plant Registrations, Vol. 4, No. 2, May 2010 CULTIVAR 133 Table 1. Mean comparison of Rondo with commercial cultivars in the fi eld tests of Uniform Regional Rice Nursery (URRN) for agronomic performance. Milling yield Cultivar Year URRN entry Type Grain yield Heading Plant height Total Head kg ha−1 d cm –––––––– % –––––––– Rondo 2006 75 L 8683 92 99 63 51 2007 75 L 9222 95 103 66 45 2008 75 L 10279 95 103 68 55 Mean 9395a† 94a 102a 66b 50c Francis 2006 40 L 8606 84 98 67 56 2007 40 L 10252 86 102 67 53 2008 40 L 10017 87 103 69 55 Mean 9625a 86bc 101a 68ab 55b Cocodire 2006 59 L 8543 84 91 71 60 2007 59 L 9062 84 95 68 55 2008 59 L 9897 84 97 70 58 Mean 9167ab 84c 94b 70a 58a Wells 2006 80 L 8458 88 100 63 53 2007 80 L 9266 88 105 68 48 2008 80 L 10200 90 106 70 55 Mean 9308a 89bc 104a 67ab 52c Priscilla 2006 57 L 8271 87 94 68 52 2007 57 L 8477 86 97 67 52 2008 57 L 9531 86 89 68 51 Mean 8760b 86bc 93b 68ab 52c Saber 2006 56 L 7940 86 95 68 59 2007 56 L 8077 86 100 66 55 2008 56 L 6401 85 84 72 57 Mean 7473c 86bc 93b 69a 57a Presidio 2006 19 L 8477 83 92 70 61 2007 19 L 8312 85 94 69 55 2008 19 L 9924 85 97 70 59 Mean 8904b 84c 94b 70a 58a †Cultivars were not signifi cantly different with same letter in the column.

Table 2. Mean comparison of Rondo with commercial cultivars in the lab and fi eld tests of Uniform Regional Rice Nursery (URRN) for cooking quality and disease resistance. Field disease Gel Cooking quality markers 0 (Immune)– 9 (Very susceptible) Entry Variety Year GT† Amyl ASV Type RVA Waxy CTs EX-6 EX-6 ALK BPB SB LB RNB NBLS % Rondo 2006 L 23.5 7.0 Low DXBL 107 11 149 High 92 3.5 4.5 0.5 0.0 0.3 75 2007 23.2 6.8 Low DXBL 107 11 149 High 92 3.8 3.5 0 0 Dixiebelle 2006 L 24.4 4.6 Int. DXBL 107 11 149 High 90 6.0 6.0 3.5 5.5 2.0 120 2007 24.6 4.3 Int. DXBL 107 11 149 High 90 4.0 6.0 5.0 1.0 Sabine 2006 L 24.4 4.5 Int. DXBL 107 11 149 High 90 4.0 7.0 1.0 5.0 5.5 159 2007 24.3 4.1 Int. DXBL 107 11 149 High 90 4.5 6.5 5.5 2.0 Cocodrie 2006 L 23.7 4.1 Int. L202 126 20 149 L202 90 6.0 8.0 0.8 4.8 2.3 59 2007 23.9 3.8 Int. L202 126 20 149 L202 90 6.0 7.3 4.5 2.3 Wells 2006 L 22.1 4.3 Int. Long 114 14 152 Int. 90 5.0 4.8 3.3 4.8 0.0 80 2007 22.1 4.0 Int. Long 114 14 152 Int. 90 5.3 5.0 2.0 0 Francis 2006 L 21.6 3.8 Int. Long 126 20 152 Int. 90 5.5 5.5 3.5 7.0 1.5 40 2007 21.7 3.3 Int. 126 20 152 Long 90 6.8 4.0 4.5 0 †GT-Grain type; Amyl-Amylose; ASV-Alkali spreading value; Gel-Gelatinization temperature; BPB-Bacterial panicle blight; SB-Sheath blight, LB-Leaf blast; RNB-Panicle neck blast and NBLS-Narrow brown leaf spot.

of new breeding lines or cultivars. Foundation seed produc- poses. Breeder seed will be maintained in the USDA-ARS, Dale tion is managed by Texas Research Improvement Association Bumpers National Rice Research Center, Stuttgart, AR (http:// at Beaumont, TX, where seed is available for commercial pur- ars.usda.gov/spa/dbnrrc; verifi ed 7 February 2010).

134 CULTIVAR Journal of Plant Registrations, Vol. 4, No. 2, May 2010 Table 3. Mean comparison of Rondo with commercial cultivars in the lab tests of Uniform Regional Rice Nursery (URRN) for common races of blast pathogen and resistance genes. Blast (Magnaporthe oryzae) race, 0 (immune) − 9 (very susceptible) Resistant gene present URRN Zn15 IB33 A598 A119 49D A264 ZN7 TM2 #24 ZN46 ID13 Pi-kh/ Entry Variety Year GT† IB-1 IB33 IB-49 IB-49 IB-49 IC-17 IE-1 Race K IG-1 IC-1 ID13 Pi-b ks Pi-ta Pi-z 75 Rondo 2006 L 03003000003YesNoNoNo 20070 00000000 NoNoNoNo 2008000 0100 0 120 Dixiebelle 2006 L 48546567774NoNoNoNo 20074 54055434 NoNoNoNo 2008577 8115 1 159 Sabine 2006 L 65656668664NoNoNoNo 20075 –6040036 NoNoNoNo 2008567 7158 0 59 Cocodrie 2006 L 05005104310NoYesNoNo 20071 00210003 NoYesNoNo 2008466 1110 0 80 Wells 2006 L 68658769070NoYesNoNo 20076 64565505 NoYesNoNo 2008677 8161 0 40 Francis 2006 L 78769769776NoNoNoNo 20077 64364675 NoNoNoNo 2008677 6448 1 †GT–Grain type. 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