Inheritance of resistance to orange rust in sugarcane

Authors: Sood, Sushma; GLYNN, NEIL - Syngenta Seeds, Inc; XIPING, YANG - University Of Florida; JIANPING, WANG - University Of Florida; McCorkle, Katherine; ROTT, PHILIPPE - University Of Florida; Comstock, Jack

Submitted to: International Society of Sugar Cane Technologists Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/1/2016
Publication Date: N/A
Citation: N/A

Interpretive Summary: Orange rust of sugarcane was first detected in Florida and the Western Hemisphere in 2007 and has been causing considerable economic losses in susceptible cultivars in Florida. The Florida sugarcane industry is using fungicides to reduce economic losses from orange rust but efforts are also focused on producing cultivars resistant to orange rust in the Canal Point breeding program. A better understanding of orange rust resistance inheritance in sugarcane will help in breeding and selection process for orange rust resistance. In this study, orange rust reactions of seedlings in progenies originating from 12 crosses between female and male parents with differing resistance to orange rust (three of each category: resistant x resistant, resistant x susceptible, susceptible x resistant, and susceptible x susceptible) were determined. In addition, two reciprocal crosses between orange rust susceptible CP88-1762 (S) and orange rust resistant CP95-1039 (R) parents were assessed for their reaction to orange rust. The progeny of two reciprocal crosses (same parents but with the male/female parents reversed) showed that the resistant female parent had twice as many orange rust resistant progeny compared with the cross with the susceptible female parent. Progenies of crosses from all combinations were composed of higher numbers of resistant plants than expected. A very high ratio of resistant individuals (R:S = 4:1) was present in the progeny of a self-cross (X03-1060) of a highly susceptible parent CP94-2203. Similar results (R:S = 3:1) were observed in the progeny of a cross between two susceptible parents (CP94-2203 X CP84-1198). Therefore, it is important not to eliminate parents susceptible to orange rust but with high agronomic value because of their ability to produce resistant genotypes in relatively high proportions.

Technical Abstract: Orange rust, caused by Puccinia kuehnii, is an economically important disease in the Florida sugarcane industry. In this study, orange rust reactions of seedlings in progenies originating from 12 crosses between female and male parents with differing resistance to orange rust (three of each category: resistant x resistant, resistant x susceptible, susceptible x resistant, and susceptible x susceptible) were determined. Ratings for orange rust for the progeny of the 12 crosses were obtained by spraying seedlings with a spore suspension (104 urediniospores/mL) and incubating them overnight in dark at 25°C in dew chambers. In addition, two reciprocal crosses between orange rust susceptible CP88-1762 (S) and orange rust resistant CP95-1039 (R) parents were assessed for their reaction to orange rust. The progeny of two reciprocal crosses (same parents but with the male/female parents reversed) showed that the resistant female parent had twice as many orange rust resistant progeny compared with the cross with the susceptible female parent. Progenies of crosses from all combinations were composed of higher numbers of resistant plants than expected. A very high ratio of resistant individuals (R:S = 4:1) was present in the progeny of a self-cross (X03-1060) of a highly susceptible parent CP94-2203. Similar results (R:S = 3:1) were observed in the progeny of a cross between two susceptible parents (CP94-2203 X CP84-1198). Therefore, it is important not to eliminate parents susceptible to orange rust but with high agronomic value because of their ability to produce resistant genotypes in relatively high proportions.