The disease resistance of the sugarcane cultivars released in the past two decade in Florida.

Authors: Sood, Sushma; BALTAZAR, MIGUEL - Florida Sugarcane League; DAVIDSON, WAYNE - Florida Sugarcane League; Islam, Md

Submitted to: International Conference on Sugar and Integrated Industries
Publication Type: Abstract Only
Publication Acceptance Date: 5/30/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: N/A

Technical Abstract: Sugarcane diseases are the main factor for the removal of cultivars from commercial production; therefore, developing high-yielding, disease-resistant cultivars is necessary for sustainable sugarcane production worldwide. Several diseases in Florida are economically important because of significant yield losses. Brown rust, caused by Puccinia melanocephala; orange rust, caused by P. kuehnii; leaf scald, caused by Xanthomonas albilineans; mosaic, caused by sugarcane mosaic virus; ratoon stunt (RSD), caused by Leifsonia xyli subsp. xyli and smut, caused by Sporisorium scitamineum, are the most economically significant diseases in Florida and the US sugarcane industry. The sugarcane breeding and development program at Canal Point (CP program), FL, has continued to select high-yielding and disease-resistant cultivars for the Florida sugarcane Industry since the 1960s. In this study, we evaluated cultivars released for commercial production in the past two decades to determine the success of our selection program for disease resistance. Sixty-nine cultivars were released from 2004 to 2023, 22 were released from 2004 to 2013, and 47 were released from 2014 to 2023. The cultivars resistant to any disease were given a score of four. Moderately resistant cultivars received a score of three for each disease, moderately susceptible cultivars received a score of two, and susceptible cultivars received a score of one. The cumulative sums of these scores for all six diseases were used for the evaluation. A higher score represents a higher resistance. The results show that the cultivars released in the past decade had a higher score than the previous decade. However, CPCL 05-1201, released in 2012 for commercial production, is resistant or moderately resistant and has a score of 23 out of 24; it has been cultivated in about 30% of the acreage in Florida. Four cultivars released in the last decade have either equal or better resistance scores than CPCL 05-1201. The resistance to orange rust has significantly increased (p<0.01) in the last decade compared to the previous decade because screening for orange rust resistance started in 2008. The resistance to brown rust, leaf scald, smut, and RSD increased significantly (p<0.05), but mosaic resistance remained the same between the two decades. Of 69 released cultivars, 57 were tested for the brown rust resistance locus (Bru1), and 32 had the Bru 1 locus. Among cultivars without the Bru1 marker, two were resistant, 12 were moderately resistant, two were moderately susceptible, and nine were susceptible to brown rust. Thirteen of 22 released cultivars between 2004 and 2013 had the Bru1 marker. However, 17 cultivars out of 33 released between 2014 and 2020 had the Bru1 marker. Cultivars that were moderately resistant and moderately susceptible to brown rust were released because the use of fungicides to control brown rust started in 2013-2014. The data suggest that the CP program has increased disease resistance throughout the past two decades, particularly in the last decade.