Brown rust, caused by Puccinia melanocephala, has had devastating effects on sugarcane (Saccharum spp.) breeding programs and commercial production. The discovery of Bru1, a major gene conferring resistance to brown rust, represented a substantial breakthrough. Markers for Bru1 are the first available for sugarcane molecular breeding. The contribution of Bru1 towards brown rust resistance in the Canal Point (CP) sugarcane breeding program was determined as a means of directing future breeding strategies. Bru1 was detected in 285 of 1,072 (27 %) clones used for crossing; this germplasm represents the genetic base for cultivar development in Florida. The frequency of Bru1 was greatest in CP clones (42 %) and lowest among Louisiana clones (6 %). Bru1 was not detected in clones with year assignments before 1953. However, Bru1 frequency increased from 15 % (assignments 1975-1985) to 47 % in the current decade. The increase coincided with the introduction of brown rust to Florida. Bru1 was detected in 155 (32 %) of 485 parental clones tested for brown rust susceptibility at two field locations. Of clones classed resistant to brown rust, 154 (59 %) contained Bru1, yet none of 100 susceptible clones contained the gene. Bru1 was detected in 667 (44 %) clones in the second clonal stage of selection, 87 % of which were free of brown rust symptoms. Bru1 is the predominant source of resistance in the Florida sugarcane genetic base. Efforts to identify and integrate new brown rust resistance genes must be pursued to minimize risks associated with a future breakdown in major gene resistance provided by Bru1. (Résumé d'auteur

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Consistent development of high-yielding sugarcane (a complex hybrid of Saccharum spp.) cultivars with resistance or tolerance to biotic and abiotic stresses is critical to commercial sugarcane production. Currently, orange rust (caused by Puccinia kuehnii E.J. Butler) is a big challenge for the sugarcane production in Florida, USA. A better understanding of sugarcane genotypic variability in response to orange rust disease will help optimize breeding and selection strategies for disease resistance. Orange rust ratings, scaled from non-infection (0) to severe infection (4) with intervals of 0.5, were recorded from genotypes at the first clonal selection stage (Stage I) of the Canal Point sugarcane breeding and cultivar development program in Florida. Data were collected from all 14,272 and 12,661 genotypes and four replicated reference cultivars, CP 78-1628, CP 80-1743, CP 88-1762 and CP 89-2143, in July-August 2012 and 2013, respectively. Mean rust rating, % of rust infection and rust severity in each family (i.e., progeny of the cross from a female and male) and female parent and their Coefficients of Variation (CV) within and among families (females) were estimated. Results indicated that considerable variation exists in rust tolerance among families or females. The families or females for their progenies with the high susceptibility or resistance to orange rust were identified and ranked. The findings of this study are useful for evaluating sugarcane crosses and parents for rust disease and can help breeders use desirable parents for crossing and improve genotypic resistance to orange rust in the sugarcane breeding programs.

‘CP 00‐1101’ (Reg. No. CV‐130, PI 651881) sugarcane (a complex hybrid of Saccharum spp.) was developed through cooperative research conducted by the USDA‐ARS, the University of Florida, and the Florida Sugarcane League, Inc., and was released to growers in Florida in September 2007. CP 00‐1101 was selected from a putative self‐cross of ‘CP 89‐2143’ made at Canal Point, FL, in January 1998. CP 89‐2143 is a major sugarcane cultivar in Florida. CP 00‐1101 was released because of its high plant cane and ratoon yields of cane and commercial recoverable sucrose on organic and sand soils, and its resistance to smut [caused by Ustilago scitaminea (Sydow & P. Sydow)], brown rust (caused by Puccinia melanocephala H. & P. Sydow), orange rust (caused by Puccinia kuehnii E.J. Butler), leaf scald (caused by Xanthomonas albilineans Ashby, Dowson), Sugarcane mosaic virus strain E (mosaic), and ratoon stunting disease (caused by Clavibacter xyli subsp. Xyli Davis) in Florida.

Sugarcane (Saccharum spp.) brown rust (caused by Puccinia melanocephala Syd. & P. Syd.) was first reported in the United States in 1978 and is still one of the great challenges for sugarcane production. A better understanding of sugarcane genotypic variation in response to brown rust will help optimize breeding and selection strategies for disease resistance. Brown rust ratings were scaled from non-infection (0) to severe infection (4) with intervals of 0.5 and routinely recorded for genotypes in the first clonal selection stage of the Canal Point sugarcane breeding program in Florida. Data were collected from 14,272 and 12,661 genotypes and replicated check cultivars in 2012 and 2013, respectively. Mean rust rating, % infection, and severity in each family and progeny of female parent were determined, and their coefficients of variation (CV) within and among families (females) were estimated. Considerable variation exists in rust ratings among families or females. The families and female parents with high susceptibility or resistance to brown rust were identified and ranked. The findings of this study can help scientists to evaluate sugarcane crosses and parents for brown rust disease, to use desirable parents for crossing, and to improve genetic resistance to brown rust in breeding programs. OPEN ACCESSAgronomy 2015, 5 342

Research to develop ‘CPCL 97‐2730’ (Reg. No. CV‐137, PI 655943) sugarcane (a complex hybrid of Saccharum spp.) was initiated by the United States Sugar Corporation (USSC) and completed cooperatively by the USDA–ARS, the University of Florida, and the Florida Sugar Cane League, Inc. CPCL 97‐2730 was released to growers in Florida in December 2008. CPCL 97‐2730 was selected from a cross of USSC proprietary genotypes CL 75‐0853 × CL 88‐4730 made at Clewiston, FL, in December 1996. The female parent, CL 75‐0853, had high commercial recoverable sucrose (CRS) but because of low cane yields was not used extensively by USSC. The male parent, CL 88‐4730, is a high‐yielding genotype that USSC is evaluating in commercial fields with sand and muck soils for possible extended use. CPCL 97‐2730 was released because of its acceptable yields of cane and CRS on sand soils and its resistance to smut (caused by Ustilago scitaminea Syd. & P. Syd.), brown rust (caused by Puccinia melanocephala Syd. & P. Syd.), orange rust [caused by P. kuehnii (Kruger) E. Butler], leaf scald [caused by Xanthomonas albilineans (Ashby) Dowson], and sugarcane mosaic virus strain E.

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CP 08-1110' (Reg. No. CV-171, PI 678579) sugarcane (a complex hybrid of Saccharum spp.) was developed through cooperative research conducted by the USDA-ARS, the University of Florida, and the Florida Sugar Cane League and was released to growers for use on mineral (sand) soils in Florida in June 2015. CP 08-1110 was selected from a biparental cross made at Canal Point, FL, on 20 Dec. 2006 with the Canal Point sugarcane breeding lines CP 01-2459 (female parent) and CP 00-2188 (male parent). CP 08-1110 was released by the Florida sugarcane variety committee because of its high cane and sucrose yields and acceptable commercial recoverable sucrose on sand soils, and because of its acceptable levels of resistance to brown rust (caused by Puccinia melanocephala H. & P. Sydow), orange rust (caused by Puccinia kuehnii E.J. Butler), leaf scald (caused by Xanthomonas albilineans Ashby, Dowson), Sugarcane mosaic virus strain E, ratoon stunt (caused by Leifsonia xyli subsp. xyli Evtsuhenko et al.), and smut [caused by Sporisorium scitamineum (Syd.) M. Piepenbring et al.]. Given the results of nine harvests with three crops (plant cane, irst ratoon, and second ratoon) at three locations in inal-stage replicated yield trials on sand soils, and compared with two reference cultivars (CP 89-2143 and CL 88-4730), CP 08-1110 had 24.9 and 30.4% higher cane yield and 18.5 and 29.0% higher sucrose yield, respectively (P < 0.05). CP 08-1110 ranked 16th (plant cane) to 19th (irst ratoon) for freeze tolerance among 22 genotypes in ield tests for temporal sucrose deterioration.