Relating cultivar Pachymetra root rot resistance to sugarcane yield using breeding selection trial analyses

Abstract

Plant breeders conduct a range of yield trials each year to estimate the yielding potential of sugarcane clones progressing through the breeding program. Only the highest-yielding clones are selected for further testing with very small numbers being released as commercial cultivars. Disease susceptibility varies greatly amongst the tested clones and a number of diseases influence the yield of clones in various stages of the selection process. Disease resistance testing is an important routine aspect of the breeding program. All clones for northern Queensland are screened for disease resistance, while selected clones from other areas are tested for resistance to Pachymetra root rot. Two new terms are introduced: resistance index (RI) and the yield loss resistance index (YLRI). Analyses were conducted relating yielding ability of clones in stage 3 trials to Pachymetra resistance. Pachymetra root rot on average reduced tonnes cane per hectare by 15.8% and tonnes sugar per hectare by 10.2%. There was a slight positive effect on commercial cane sugar. YLRI5 for tonnes cane was 3.5 and for tonnes sugar 5.7. With a RI of 3.7, the current breeding strategy for northern Queensland appears appropriate. The data reported here will be valuable for refining selection strategies to improve breeding efficiencies. These analyses could be undertaken each year using data from all breeding trials throughout Queensland, not only with Pachymetra root rot, but also with other diseases normally endemic in cane fields. The advantage of this technique is that with a minimum of further expenditure, ongoing estimates of disease-induced yield losses can be obtained with the information guiding the selection program.

Effects of orange rust on sugarcane yield traits in a multi-environment breeding program

“…Resistance to orange rust is controlled by a few major Quantitative Trait Alleles (QTAs) (Yang et al 2018), whereas yield traits are controlled by a very large number of QTAs each with little effect (Hoarau et al 2002;Reffay et al 2005;Piperidis et al 2008;Aitken et al 2006Aitken et al , 2008. Finally, the slope of the regression line was used to estimate a yield loss resistance index (YLRI 5 ) as defined by Magarey and Bull (2003). YLRI 5 is a level of resistance inferred from the regression line and for which yields are 5% lower than the yields of the most resistant varieties.…”

Isolation and sequencing of a single copy of an introgressed chromosome from a complex genome for gene and SNP identification

“…Yield loss from nematodes are estimated at 12 to 15%, costing the Australian sugar industry about AU$82 million per year (Blair and Stirling 2007). Similar yield losses, 10 to 15% are estimated for Pachymetra root rot, with up to nearly 40% losses in susceptible varieties (Magarey and Bull 2003). E. arundinaceus is a hexaploid and contains 60 chromosomes making whole genome sequencing and assembly very costly but introgression can be used to reduce the number of chromosomes.…”