VIEW ARTICLE

Genetics

Heritability of Resistance and Repeatability of Clone Reactions to Sugarcane Smut in Louisiana. C. P. Chao, Former graduate assistant, Department of Plant Pathology, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803, Present address: Taiwan Banana Research Institute, P.O. Box 18, Chiuju, Pingtung 90403, Republic of China; J. W. Hoy(2), A. M. Saxton(3), and F. A. Martin(4). (2)Associate professor, Department of Crop Physiology, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803; (3)Associate professor, Department of Experimental Statistics, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803; (4)Professor, Department of Agronomy, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803. Phytopathology 80:622-626. Accepted for publication 24 January 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/Phyto-80-622.

Heritability of resistance to sugarcane smut caused by Ustilago scitaminea was estimated by comparing percentages of shoot smut infection of parents and offspring from 18 biparental crosses involving resistant, moderately susceptible, and highly susceptible clones. Frequencies of resistant offspring were highest in resistant ? resistant crosses. Narrow-sense heritability estimates, determined by mid-parent-offspring regressions in plant cane (first-season crop) and first ratoon (second-season crop) were 0.41 ? 0.08 and 0.38 ? 0.11, respectively. Estimated genetic gains in resistance ranged from 5 to 13% depending upon the assumed selection intensity. Estimates of repeatability of smut reactions of parents in two plant cane crops and from plant cane to first ratoon were 0.60 ? 0.10 and 0.75 ? 0.07, respectively. The repeatability estimate for offspring from plant cane to first ratoon was 0.62 ? 0.08. Disease reactions of experimental cultivars in breeding program smut inoculation tests also were moderately repeatable between plant cane and first ratoon and subsequent plant cane or first ratoon crops. Repeatability estimates for clones rated as resistant, moderately susceptible, or highly susceptible to smut in plant cane were moderate for resistant and highly susceptible clones and low for moderately susceptible clones in two populations between plant cane and first ratoon. Smut resistance ratings assigned to clones were significantly correlated between crops and in different years. The results suggest that the proportion of resistant progeny can be increased by minimizing the use of susceptible parents and that plant cane infection ratings from multiple inoculation tests are needed to accurately assess sugarcane clone smut susceptibility.