Breeding Perennial Ryegrass for Resistance to Gray Leaf Spot

Abstract

genic races; thus, host resistance genes remain effective for only a few years before the pathogen population Gray leaf spot, caused by the fungus Pyricularia grisea (Cooke) shifts to new virulent races (Bonman et al., 1992; Zhu Sacc. [teleomorph Magnaporthe grisea (T.T. Herbert) Yaegashi & Udagawa], can be a devastating disease on perennial ryegrass (Lolium et al. , 2000). This has led researchers to identify durable perenne L.). The identification and utilization of perennial ryegrass (quantitative) resistance mechanisms to more successcultivars with improved resistance to gray leaf spot would reduce the fully prevent disease outbreaks in rice (Ahn and Ou, need for fungicide applications. The objectives of this study were to: 1982; Cho et al., 1998). Chen et al. (2003) have studied (i) evaluate cultivars, experimental selections, and single-plot progequantitative disease resistance to rice blast using a renies of perennial ryegrass for resistance to gray leaf spot, (ii) develop combinant inbred line population in rice and a barley populations from selected resistant parents to determine improve-(Hordeum vulgare L.) double haploid population. They ments in the next generation, and (iii) determine heritability and the found quantitative trait loci associated with resistance response to selection for gray leaf spot resistance in perennial ryegrass in both populations and suggested that there may be populations. Two perennial ryegrass field experiments consisting of synteny in the quantitative trait loci (QTL) of blast commercial cultivars and experimental selections, were established in 2000 and 2001 at Adelphia, NJ. Susceptibility of germplasm to gray resistance between barley and rice genomes. The simileaf spot was evaluated following ephemeral natural outbreaks of the larity in QTL between rice and barley indicates that disease that occurred three to four weeks post seeding. Parents with similar resistance mechanisms may be employed by difimproved resistance to gray leaf spot were selected based on progeny ferent grass species, including perennial ryegrass. Returf plot evaluations in 2000, inter-pollinated and seeded into turf sults of Curley et al. (2003) support this hypothesis. plots in the 2001 experiment. Most cultivars and selections evaluatedSince the first report of gray leaf spot disease on in both experiments had greater than 50% gray leaf spot disease. The perennial ryegrass turf in 1991, the disease has spread high broad-sense heritability estimate (0.92) and similar response of from the transition zone, through the Mid-Atlantic states progeny compared to selected parents indicated that parent selection and north to New England (Schumann, 1999), as well as based on progeny tests was a good selection method to predict the west through Indiana (Harmon et al., 2000) and Illinois combining ability of the parents. It also proved successful in improving gray leaf spot resistance in the next generation, which will be important

Inheritance of Resistance to Gray Leaf Spot Disease in Perennial Ryegrass

“…This study agrees with the former study (Bonos et al, 2004) in that resistance could be rapidly improved through a genotypic recurrent selection program. However, additive gene effects were the major factor in gray leaf spot resistance evaluated in these perennial ryegrass plants.…”

“…Bonos et al (2004) reported that a major gene for gray leaf spot resistance was segregating in the resistant perennial ryegrass populations. Assumedly, there could be more than three to five genes involved in gray leaf spot resistance in these crosses.…”

Breeding Cool‐Season Turfgrass Cultivars for Stress Tolerance and Sustainability in a Changing Environment

“…By incorporating native germplasm into naturalized populations, genetic diversity increases, which can result in the development of cultivars with improved traits or increased fitness. One example of this is the development of gray leaf spot (caused by Pyricularia oryzae) disease resistance in perennial ryegrass cultivars (Bonos et al, 2004). When the disease was first reported in North America, no commercial cultivars were found with gray leaf spot resistance.…”

“…When the disease was first reported in North America, no commercial cultivars were found with gray leaf spot resistance. After an epidemic of gray leaf spot in 2000, ~13% of the Rutgers perennial ryegrass germplasm contained some level of gray leaf spot resistance (Bonos et al, 2004). Approximately 50% of the resistant germplasm traced to plants collected from North America and 50% traced to European collections that had been backcrossed with North American germplasm.…”

Magnaporthe oryzae isolates causing gray leaf spot of perennial ryegrass possess a functional copy of the AVR1‐CO39 avirulence gene

“…Unfortunately, under the current situation, this approach does not promise to be all that useful for managing gray leaf spot because most prg germplasm is susceptible to the disease (Hofmann and Hamblin, 2000; Vaiciunas and Clarke, 1998). Nevertheless, a small number of cultivars with improved levels of resistance have been recently developed and released for public use (Bonos et al ., 2004; Cai et al ., 1997; Samudio and Brede, 2004). In these cases, resistance functions by reducing disease severity and, as such, is quantitative in nature.…”