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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Core Ideas Energy cane may be an alternative crop on sand soils in the future to improve profits. It is unclear if energy cane differs from sugarcane in physiology and yield on sand soils. Energy cane had 26 to 35% greater normalized difference vegetation index and 21% higher yield than sugarcane. Increased yield of energy cane was associated with great normalized difference vegetation index and high stalk population rather than leaf net photosynthetic rate. A growing interest of producing sugarcane (a complex hybrid of Saccharum spp.) for both sugar and bioenergy and saturation of using organic soils provide an opportunity to expand production on mineral (sand) soils. However, sugarcane yields and profits on sand soils are generally low. Energy cane may be an alternative on sand soils in the future to improve profits. The objective of this study was to identify physiological and biomass traits of sugarcane and energy cane growing on sand soils. Two commercial sugarcane cultivars and two energy cane clones were planted at two sites with sand soils in southern Florida. Data were collected on plant‐cane, first‐ratoon, and second‐ratoon crops. Leaf relative chlorophyll level (SPAD), photosynthetic rate (Pn), and canopy reflectance were measured during tillering and grand growth. Normalized difference vegetation index (NDVI) was calculated based on canopy reflectance data. Stalk population, diameter and length, and aboveground biomass yields were determined when plants reached maturation. Although there were no consistent differences between sugarcane and energy cane in leaf SPAD, Pn or NDVI of plant cane, energy cane had 26 to 35% greater NDVI values than sugarcane in the ratoon crops. Energy cane showed 21% higher dry biomass than sugarcane, averaged across sites and crops. Increased biomass production of energy cane was mainly associated with high stalk population, long stalk, and great NDVI rather than leaf Pn or stalk diameter. The findings of this study on physiological parameters of energy cane vs. sugarcane can be useful for improvement of knowledge and future research.

Growth, yield, and yield components of sugarcane (a complex hybrid of Saccharum spp.) are important traits for growers to evaluate cultivars and for scientists to select best genotypes in the breeding and cultivar development programs. Collection of these yield data across genotypes would be labor intensive and time consuming in the early selection stages of the breeding programs with a large number of genotypes. A field experiment was conducted on a sand soil to investigate physiological and yield characteristics of 18 sugarcane genotypes and to determine relationships of leaf relative chlorophyll (SPAD reading), leaf net photosynthetic rate (Pn), and canopy normalized difference vegetation index (NDVI) with yield traits, including stalk population, length, diameter, weight, cane yield (tonnes of cane per hectare [TCH]), commercial recoverable sucrose, and sucrose yield (tonnes of sucrose per hectare [TSH]) across genotypes. The NDVI values were calculated based on canopy reflectance in the red (680 nm) and near‐infrared (800 nm) spectra measured using a multispectral radiometer. Among yield traits, stalk population and TCH were most highly correlated with NDVI and/or Pn. Although stalks and TCH were highly and linearly (P < 0.0001) related to NDVI measured in April to August, the best stage of measuring NDVI for yield assessment in Florida across genotypes was during tillering and early grand growth (before canopy closure). Therefore, measurements of NDVI before canopy closure could be useful for predicting plant growth and yield potential across genotypes in cultivar selection programs and used as an agronomic management tool in sugarcane production.

Bagasse is an agricultural by-product derived from the sugarcane milling process. It is a dry and fibrous residue left after the extraction of sugar juice from sugarcane. Over 2 million metric tons of bagasse is generated each year in South Florida, and need exists to find environmentally sustainable, yet economically viable use for it. Application of bagasse as a potential soil amendment on mineral soils to grow sugarcane seems like a good option to utilize the product. This factsheet explores the feasibilty of using bagasse as a organic soil amendment to grow sugarcane on mineral soils in South Florida.