Field Evaluation of Sugarcane Orange Rust for First Clonal Stage of the CP Cultivar Development Program

Abstract

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.

Screening for Sugarcane Brown Rust in the First Clonal Stage of the Canal Point Sugarcane Breeding Program

“…On the other hand, the differences in rust severity were relatively less among cultivars or between years compared with % infection (Table 1). These results are consistent to those of orange rust in sugarcane [19]. Formal statistical tests of brown rust severity were not available because CP 89-2143 and CP 88-1762 had either no plots or only one to two lots were infected.…”

“…Clone numbers among families ranged from 1 to 214 with a mean of 25 in 2012, and from 1 to 209 with a mean of 28 in 2013, and their CVs in two years were 113% and 100%, respectively ( Table 2). This substantial variability in the number of clones among families is probably associated with differences in the number of viable seeds per cross in the crossing stage, variability in the number of seedlings planted per family in the seedling stage, and variable selection rates among families in the seedling stage [19]. On a family basis, mean brown rust ratings ranged from 0.0 to 2.5 in 2012 and from 0.0 to 2.2 in 2013.…”

“…Large variability in the number of clones and in the rust ratings (Table 2) among families in Stage I of the CP program suggested that Stage-I data can be used to identify useful parental combinations and individual parents for their progeny in resistance/tolerance to rusts in the test years. As variation in sugarcane orange rust discussed by Zhao et al [19], the greater CV for rust rating within families than among families suggests that placing more emphasis on both individual clonal evaluation and family-based evaluation in Stage I of the CP program may help improve our knowledge and ability to select genotypes with potential for eliminating the negative effects of rusts on sugarcane growth and yields. …”

“…Butler), are great challenges for sustainable sugarcane production in Florida [19]. Most dominant commercial cultivars in Florida are susceptible to one or both rusts ( Figure 1).…”

“…The data collected from these two years under natural infection conditions could partly reflect genotype variation in brown rust resistance or susceptibility. In this paper, we mainly focused on sugarcane brown rust because findings of sugarcane orange rust have been reported in a current article [19].…”