Analysis of Accumulation Patterns of Barley yellow dwarf virus-PAV (BYDV-PAV) in Two Resistant Wheat Lines

Abstract

Barley yellow dwarf (BYD) is one of the main viral diseases of small-grain cereals. This disease, reported on numerous plant species of the Poaceae family, is caused by a complex of eight viral species including the species Barley Yellow Dwarf Virus-PAV (BYDV-PAV), frequently found in western Europe. Resistance sources against BYDV-PAV are scarce and only identified in perennial Triticineae. Some BYDV-resistant wheat lines have been obtained by introgressing these resistances into bread wheat germplasms. Genetic and biological characterization of the resulting lines has been undertaken. However, little information on the resistant behaviour of these lines during the early stages of the infection process is available. To evaluate the resistance of two genetically distinct resistant lines (Zhong ZH and TC14), 1740 young plantlets, belonging to susceptible reference hosts (barley cv. Express and wheat cv. Sunstar), Zhong ZH or TC14 wheat lines, were inoculated in controlled conditions with French BYDV-PAV isolates. The infection process was monitored during the first 21 days after inoculation (DAI) using a semi-quantitative ELISA. A standardized protocol including five successive samplings of leaves from all inoculated plants and the collection of plant roots at the end of the monitored period was carried out. This protocol enabled an assessment of the infection percentage and the evolution of the viral load in plants from the 7th DAI to the 21st DAI. Statistical analyses of the BYDV infection kinetics using raw ELISA data, a model of the timedependent variation of the percentage of infected plants and the area under concentration progress curves (AUCPC) demonstrated that Zhong ZH and TC14 lines (1) reduce the development rate of the BYD disease during the first days of infection, (2) decrease the infection efficiency of BYDV-PAV isolates, in the leaves, from 98.7% for susceptible plant genotypes to 81.9% and 71.7% for Zhong ZH and TC14, respectively, (3) reduce the virus load in the leaves of infected plants and (4) are not spared from BYDV infection, as 95.1% of Zhong ZH and 90.2% of TC14 inoculated plants accumulated viral particles in roots and/or in leaves at 21 DAI. These results confirm the BYDV-partial resistant behaviour of both Zhong ZH and TC14 lines. The development rate of the disease was the single parameter that allowed the distinction between the two resistant sources present in the tested lines.

Evaluation of the durability of the Barley yellow dwarf virus-resistant Zhong ZH and TC14 wheat lines

“…As previously described ( Barloy et al, 2003;Chain et al, 2005), the initial collected data (infection percentages and viral titers in infected plants) corresponding to passages 2 to 4 confirmed the partial resistance behaviour of these two wheat lines (reduced number of infected plants, lower virus titer in leaves and longer time between inoculation and initial detection of the virus). However, the use of these resistant lines as the single obligatory host in SPEs induced a rapid change of the biological properties of the used BYDV isolate.…”

“…After a 5-day inoculation access period, aphids were killed by spraying plants with insecticide (lambda-cyhalothrine, 1 mg ml )1 , Karate´Ò[Syngenta agro]). Infection parameters (percentage of infected plants and viral titers) of the inoculated plants were monitored using semi-quantitative ELISA performed 7, 11, 14, 17 and 21 days after inoculation (DAI) as described by Chain et al (2005). Twentyone DAI, virus-free aphids were deposited at the base of infected plants (4 plants per genotype) for a 3-day acquisition access period (AAP).…”

“…Data for passage 44-114 were gathered as follows: twenty plants from each of the four tested genotypes were separately inoculated with BYDV-PAV isolates obtained after passages 44, 62 and 110. In addition, 20 plants of each host genotype were inoculated with PAV Express from passages 66, 94, 106 and 114 (three aphids/plant) and infection kinetics was monitored as described by Chain et al (2005).…”

“…Zhong ZH, a ditelosomic addition line derived from Zhong 5, a partial amphiploid, (Barloy et al, 2003) and TC14, a translocated line (Banks et al, 1995), are now available. Their biological and physiological properties are well documented in the literature (Nie et al, 1996;Tang et al, 2000;Ayala et al, 2001;Chain et al, 2005). However, prior to being extensively used in breeding programmes to produce BYDV-resistant bread wheat cultivars, resistance carried by Zhong ZH and TC14 lines must be tested for durability.…”

The complete nucleotide sequence of the genome of Barley yellow dwarf virus-RMV reveals it to be a new Polerovirus distantly related to other yellow dwarf viruses

“…Perry et al (Perry et al, 2000) found an average of 30% yield loss in affected winter wheat fields. Significant agricultural research efforts are aimed at reducing the impact of the YDVs on the yield of the various crop systems by (i) altering planting time and/or pesticide application regimes to avoid the accumulation of high densities of aphids, (ii) tilling practices, and (iii) developing virus-resistance crop varieties (Chain et al, 2005; Royer et al, 2005; Kennedy and Connery, 2012). …”