Characterization of Resistance Mechanisms in Faba Bean (Vicia faba) against Broomrape Species (Orobanche and Phelipanche spp.).

Diego Rubiales,Maria M Rojas-Molina,Josefina C Sillero

doi:10.3389/fpls.2016.01747

Abstract

Faba bean (Vicia faba) production in Mediterranean and Near East agriculture is severely constrained by broomrape infection. The most widely distributed broomrape species affecting faba bean is Orobanche crenata, although O. foetida and Phelipanche aegyptiaca are of local importance. Only moderately resistant cultivars are available to farmers. Rizotrons studies allowed the dissection of resistance components in faba bean accessions against the very infective species O. crenata, O. foetida var. broteri and P. aegyptiaca, and to the inappropriate P. ramosa and O. foetida var. foetida. Results confirm that some levels of incomplete resistance are available, resulting in a reduced number of broomrape tubercles successfully formed per faba bean plant. Interestingly, the intermediate levels of resistance of cv. Baraca were operative against all broomrape populations and species studied, confirming previous reports on the stability of resistance of Baraca in field trials in different countries. Low induction of seed germination played a major role in the resistance against the inappropriate O. foetida var. foetida but not against the also inappropriate P. ramosa, neither to the infective species O. crenata, O. foetida var. broteri, or P. aegyptiaca. Negative tropism of germinated seeds with radicles growing away from faba bean roots was marked for both inappropriate species but was not observed in any of the infective species. Also, a proportion of radicles that had successfully contacted faba bean roots became necrotic, failing in starting tubercle development, particularly frequent for the two inappropriate species. Such necrosis was significant also on radicles contacting resistant faba bean accessions, being particularly relevant for Spanish O. crenata population, and lower although still significant in some accessions against Syrian O. crenata and P. aegyptiaca, suggesting that this might also be an operative mechanism to be selected and further exploited in faba bean resistance breeding. Even formed broomrape tubercles might later become necrotic, particularly in the case of some of the resistant faba bean accessions to the Spanish O. crenata and to P. aegyptiaca but not to the very infective Syrian O. crenata or O. foetida var. broteri.

Highlights

MATERIALS AND METHODSFaba bean (Vicia faba L.) is a temperate grain legume of high importance as human food and animal feed (Rubiales, 2010)
Accessions ILB4350, ILB4347, and ILB4351, previously selected as resistant in Spanish trials proved resistant to the Spanish O. crenata population in the rhizotron test, but they were more resistant than the susceptible check to Syrian one, this resistance was significantly weaker to this isolate
Prothabon that was included in the study as check due to its known susceptibility to O. crenata in Spanish fields was significantly less susceptible to the Syrian isolate and to O. foetida var. broteri than VFM26, and interestingly very resistant to P. aegyptiaca

Summary

Introduction

MATERIALS AND METHODSFaba bean (Vicia faba L.) is a temperate grain legume of high importance as human food and animal feed (Rubiales, 2010). Crenate broomrape (Orobanche crenata Forsk.) is the most damaging and widespread species infecting faba bean (Parker, 2009; Rubiales and Fernández-Aparicio, 2012; Fernández-Aparicio et al, 2016). P. aegyptiaca is a very damaging species on vegetable crops prevalent in the Eastern Mediterranean and Near East that can affect faba bean (Parker, 2009). O. ramosa L.) is very similar to P. aegyptiaca and can only very occasionally slightly infect faba bean, at low levels, not having raised major concerns on faba bean growers

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