Partial resistance to wheat leaf rust in 18 spring wheat cultivars

Abstract

Eighteen spring wheat cultivars were tested in microfields and race nurseries for their partial resistance PR to wheat leaf rust under low and high disease pressure respectively Large differences existed between the 18 cultivars, Skalavatis 56 being the most susceptible and Ponta Grossa 1 being the most resistant cultivar Of the three epidemic parameters, disease severity (DS) at the time that the susceptible check was severely diseased and area under the transformed disease severity curve (AUTC) and the logistic growth rate (r), AUTC and DS were highly correlated Both seemed to be reliable estimators of PR but DS should be preferred for economical reasons The logistic growth rate seemed to be unsuitable as an estimator of partial resistanceHigh and low disease pressure gave similar cultivar ranking PR can be screened and selected equally well in race nurseries with low space, low time and low cost input as in microfields with high space, time and cost input Cultivar differences in development rate had a large impact on the cultivar differences for amount of disease and can therefore greatly bias the estimation of cultivar resistance The resistance of early cultivars tended to be underestimated whereas the resistance of late cultivars tended to be overestimated The effect of differences in developmental rate was most pronounced in the flag leaf It is advisable to avoid the assessment of disease levels on the flag leaf only and to incorporate in the tests several susceptible and resistant checks that cover the range of development rates in the material to be selected, because otherwise selection for resistance will tend to select also for lateness Regression of the epidemiological parameters on three components of partial resistance revealed that latency period (LP) is an important factor in determining the resistance observed in the field explaining on average 67% of the observed variation Adding infection frequency (IF) and urediosorus size (US) to the linear model increased the proportion of the observed variation in the field explained by the components to 80% This result supports the idea that the components of PR inherit independently, at least, in part 248

Evaluation of wheat cultivars for slow rusting resistance to leaf rust (Puccinia trticina Eriks) in Ethiopia

“…Therefore infection rate in the present study seemed to produce unreliable estimates of slow rusting resistance when compared with FRS, CI and AUDPC. Similar results were found for rusts of wheat (Rees et al, 1979;Broers, 1989;Ali et al, 2008;Safavi et al, 2013).…”

Application of Phenotypic and Molecular Markers to Combine Genes for Durable Resistance against Rust Virulences and High Yield Potential in Wheat

“…The most efficient and economical management of wheat rusts is the generation of rust resistant varieties and their on-farm cultivation Hussain et al, 1999;Kalappanavar et al, 2008). In the present era of scientific advancement, the wheat research is focused to achieve durable rust resistance through incorporation of multiple minor genes or adult plant resistance genes (Broers, 1989;Singh and Rajaram, 1991;Singh et al, 2000;Rehman et al, 2013). The worst yellow rust epidemics in 2005 and 2012 have wiped out major commercial wheat varieties of Pakistan (Khan et al, 2005;Hussain et al, 2015).…”

“…At present country is facing critical shortage of appropriate wheat varieties having both features of high yield and rust resistance to leaf, yellow and stem rust (Hussain et al, 2006). Now a days, pathologists and breeders have sought resistance mechanism based on minor genes which is called durable rust resistance or adult plant resistance (Broers, 1989;Singh and Rajaram, 1991;Singh et al, 2000). This type of rust resistance mechanism is more effective for many races rather than a single one and is long lasting Hussain et al, 1999;Bariana et al, 2001).…”

Quantitative resistance and its components in 16 barley cultivars to yellow rust, Puccinia striiformis f. sp. hordei

“…Quantitative resistance to P. hordei in barley (Parlevliet and Van Ommeren 1975) and to P. triticina in wheat is partial (Ohm and Shaner 1976;Broers 1989b), and is characterized by a susceptible infection type (IT) in both the seedling and the adult plant stages combined with a slow rate of disease development. It is therefore partial sensu Parlevliet (Parlevliet and Van Ommeren 1975).…”