Growth stage‐dependent resistance to the potyviruses lettuce Italian necrotic virus and Lettuce mosaic virus displayed by Lactuca sativa introgression lines carrying the Mo3 locus from L. virosa

Abstract

The single dominant gene Mo3 from accession PIVT1398 of Lactuca virosa was shown previously to confer resistance to all tested isolates of Lettuce mosaic virus (LMV; genus Potyvirus), including mo1‐resistance‐breaking isolates. Because accession PIVT1398 is also resistant to the recently described potyvirus lettuce Italian necrotic virus (LINV), this study checked whether the Mo3 resistance locus could be involved in resistance to LINV. Introgression lines of Mo3 into two different L. sativa genetic backgrounds (Girelle and Mantilia) were resistant to isolates LMV‐9, LMV‐13 and LINV‐Fr (a French isolate of LINV), whereas Girelle and Mantilia were susceptible to these virus isolates. The resistance reaction in inoculated leaves of the introgression lines varied from absence of symptoms and absence of virus detection for LMV‐9, to hypersensitive‐like necrotic lesions and low virus titres for LINV‐Fr and large necrotic lesions and relatively abundant virus detection for LMV‐13. At the systemic level, the resistance phenotype was growth stage‐dependent for LINV‐Fr and LMV‐13. Inoculation of ≥28‐days‐old plants led to absence of symptoms and no virus with the three tested potyvirus isolates in almost all plants. Inoculation of younger plants (≤22‐days‐old) led to chlorotic/necrotic lesions on some apical leaves with low virus titre in a varying proportion of plants with LINV‐Fr and on all plants with efficient virus detection with LMV‐13. These results show that the Mo3 gene, or a tightly linked locus, in L. virosa PIVT1398 controls resistance to LINV in addition to LMV and could be used to breed L. sativa cultivars with broad‐spectrum potyvirus resistance.

The INRAE Centre for Vegetable Germplasm: Geographically and Phenotypically Diverse Collections and Their Use in Genetics and Plant Breeding

“…The lettuce collection is completed by 15 accessions from other genera of the Asteraceae family ( Chondrilla , Mycelis , Sonchus ). The lettuce collection contains a few lines with resistance to potyviruses or Bremia lactuca identified in L. virosa and introgressed into a cultivated background [ 42 , 43 , 44 ].…”

“…The hybrids with L. virosa are sterile and often show physiological disorders such as necrosis or stunted plants, which are difficult to eliminate in any progenies that are obtained [ 101 ]. Resistant genes from L. virosa have been introgressed into a butterhead background to produce lines with new resistance to Bremia [ 103 ] and two potyviruses [ 43 , 44 ]. More than 400 lettuce accessions have also been tested with three stimulators of plant defences; some interesting protection against B. lactucae was obtained with a few cultivars [ 104 ].…”

“…For lettuce breeding, resistance to Lettuce mosaic virus (LMV), identified in L. virosa PIVT1398 [ 42 ], was introduced into butterhead lines by INRAE [ 101 ]. The NILs with the Mo3 locus were also resistant to another potyvirus: lettuce Italian necrotic virus (LINV) [ 44 ]. Some NILs with the Mo3 resistance gene have been made available for research and breeding [ 43 ].…”

Host Plant Strategies to Combat Against Viruses Effector Proteins

“…Most plant viruses possess RNA as their genome along with a coat protein called capsid, and a few viruses contain DNA [ 9 ]. Viral infections cause tremendous damage to crop plants, including chlorosis, necrosis, vein clearing, and wilting, thus affecting the physiology and morphology of plants [ 10 , 11 ]. Once a virus enters the plant cell, it can easily infect nearby cells through cell junctions, namely plasmodesmata (Fig.…”

Genetic Resistance of Lactuca spp. against Fusarium oxysporum f. sp. lactucae Race 1

“…Wildtype accessions are valuable sources of resistance against several lettuce pathogens, including the oomycete Bremia lactucae that causes lettuce downy mildew, the Lettuce mosaic virus, and the fungus Verticillium dahliae that causes verticillium wilt (Lebeda et al, 2014;Sandoya et al, 2021;Sequiera, 1978). Recently, several sources of resistance have been identified among accessions of L. georgica, L. saligna, L. serriola, and L. virosa for the pathogens Golvinomyces bolayi causing lettuce powdery mildew, B. lactucae, and Lettuce mosaic virus (Beharav, 2021;Giesbers et al, 2018;Maisonneuve et al, 2018;Pelgrom et al, 2019). Hundreds of wildtype accessions are deposited in the U.S. Department of Agriculture Germplasm Information Network (USDA-GRIN) and remain unexplored for novel sources of Fol resistance.…”