Rapid and efficient estimation of pea resistance to the soil-borne pathogen fusarium oxysporum by infrared imaging

Fusarium wilts are widespread diseases affecting most agricultural crops. In absence of efficient alternatives, sowing resistant cultivars is the preferred approach to control this disease. However, actual resistance sources are often overcome by new pathogenic races, forcing breeders to continuously search for novel resistance sources. Selection of resistant accessions, mainly based on the evaluation of symptoms at timely intervals, is highly time-consuming. Thus, we tested the potential of an infra-red imaging system in plant breeding to speed up this process. For this, we monitored the changes in surface leaf temperature upon infection by F. oxysporum f. sp. pisi in several pea accessions with contrasting response to Fusarium wilt under a controlled environment. Using a portable infra-red imaging system we detected a significant temperature increase of at least 0.5 °C after 10 days post-inoculation in the susceptible accessions, while the resistant accession temperature remained at control level. The increase in leaf temperature at 10 days post-inoculation was positively correlated with the AUDPC calculated over a 30 days period. Thus, this approach allowed the early discrimination between resistant and susceptible accessions. As such, applying infra-red imaging system in breeding for Fusarium wilt resistance would contribute to considerably shorten the process of selection of novel resistant sources. © 2015 by the authors; licensee MDPI, Basel, Switzerland.This work was supported by the European KBBE project ABSTRESS (FP7-KBBE-2011-5-289562) and the AGL2011-22524 of the Spanish Ministry of Science and Innovation and co-financed by European fund for regional development (FEDER). Nicolas Rispail is holder of a Ramón y Cajal postdoctoral position from the Spanish Ministry of Economy and Competitiveness. We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI).Peer Reviewe

Unveiling common responses of Medicago truncatula to appropriate and inappropriate rust species.

Little is known about the nature of effective defense mechanisms in legumes to pathogens of remotely related plant species. Some rust species are among pathogens with broad host range causing dramatic losses in various crop plants. To understand and compare the different host and nonhost resistance (NHR) responses of legume species against rusts, we characterized the reaction of the model legume Medicago truncatula to one appropriate (Uromyces striatus) and two inappropriate (U. viciae-fabae and U. lupinicolus) rusts. We found that similar pre and post-haustorial mechanisms of resistance appear to be operative in M. truncatula against appropriate and inappropriate rust fungus. The appropriate U. striatus germinated better on M. truncatula accessions then the inappropriate U. viciae-fabae and U. lupinicolus, but once germinated, germ tubes of the three rusts had a similar level of success in finding stomata and forming an appressoria over a stoma. However, responses to different inappropriate rust species also showed some specificity, suggesting a combination of non-specific and specific responses underlying this legume NHR to rust fungi. Further genetic and expression analysis studies will contribute to the development of the necessary molecular tools to use the present information on host and NHR mechanisms to breed for broad-spectrum resistance to rust in legume species.Financial support by Spanish AGL2011-22524 and Portuguese PEst-OE/EQB/LA0004/2011 grants is acknowledged. Maria Carlota Vaz Patto was supported by Fundação para a Ciência e a Tecnologia (Incentivos 2014 program).Peer Reviewe

Can we breed for durable resistance to broomrapes?

The broomrapes (Orobanche and Phelipanche) are parasitic plants that have modified biology to feed on other plants, completely losing autotrophic capability. Some broomrape species have adapted to agricultural ecosystems becoming parasitic weeds. The most damaging weedy broomrapes are O. crenata, O. foetida, O. minor, O. cumana, O. cernua and P. ramosa and P. aegyptiaca, which can severely constrain important dicotyledonous crops, mainly in the Mediterranean Basin. This adaptation is an active process, with recent instances of jumps from non-weedy to weedy behavior, such as for O. cumana adapting to infect sunflower little more than a century ago; O. cernua adapting to infect tomato, tobacco and eggplant; and the more recent example of O. foetida adapting to infect faba bean a few decades ago. This also relates to parasite speciation towards particular hosts, such as the ongoing process of P. ramosa populations infecting winter oilseed rape. Sunflower is a unique situation, in which highly effective monogenic resistances to broomrape have been identified and widely deployed by sunflower breeders. This was accompanied by the subsequent appearance and spread of new races of O. cumana overcoming the introduced host resistance genes. In contrast, only quantitative resistances were identified and exploited by breeders in other crops against other broomrapes. Achievements and prospects for broomrape resistance breeding are presented and critically discussed, along with complementary measures needed to preserve durability of resistance. Particularly important is the prevention of human-driven broomrape seed dispersal by crop seed trade, together with broomrape seed soil-bank demise

Clarification on Host Range of Didymella pinodes the Causal Agent of Pea Ascochyta Blight

Didymella pinodes is the principal causal agent of ascochyta blight, one of the most important fungal diseases of pea (Pisum sativum) worldwide. Understanding its host specificity has crucial implications in epidemiology and management; however, this has not been clearly delineated yet. In this study we attempt to clarify the host range of D. pinodes and to compare it with that of other close Didymella spp. D. pinodes was very virulent on pea accessions, although differences in virulence were identified among isolates. On the contrary, studied isolates of D. fabae, D. rabiei, and D. lentil showed a reduced ability to infect pea not causing macroscopically visible symptoms on any of the pea accessions tested. D. pinodes isolates were also infective to some extend on almost all species tested including species such as Hedysarum coronarium, Lathyrus sativus, Lupinus albus, Medicago spp., Trifolium spp., Trigonella foenum-graecum, and Vicia articulata which were not mentioned before as hosts of D. pinodes. On the contrary, D. lentil and D. rabiei were more specific, infecting only lentil and chickpea, respectively. D. fabae was intermediate, infecting mainly faba bean, but also slightly other species such as Glycine max, Phaseolus vulgaris, Trifolium spp., Vicia sativa, and V. articulata. DNA sequence analysis of the nuclear ribosomal internal transcribed spacer region (ITS) was performed to confirm identity of the isolates studies and to determine phylogenetic relationship among the Didymella species, revealing the presence of two clearly distinct clades. Clade one was represented by two supported subclusters including D. fabae isolates as well as D. rabiei with D. lentil isolates. Clade two was the largest and included all the D. pinodes isolates as well as Phoma medicaginis var. pinodella. Genetic distance between D. pinodes and the other Didymella spp. isolates was not correlated with overall differences in pathogenicity. Based on evidences presented here, D. pinodes is not specialized on pea and its host range is larger than that of D. fabae, D. lentil, and D. rabiei. This has relevant implications in epidemiology and control as these species might act as alternative hosts for D. pinodes.This work was supported by Spanish project AGL2014-52871-R. EB was granted by a contract founded by the Spanish JAEdoc program and MC by the Spanish Juan de la Cierva program.Peer reviewe

Application of Crop Growth Models to Assist Breeding for Intercropping: Opportunities and Challenges

Intercropping of two or more species on the same piece of land can enhance biodiversity and resource use efficiency in agriculture. Traditionally, intercropping systems have been developed and improved by empirical methods within a specific local context. To support the development of promising intercropping systems, the individual species that are part of an intercrop can be subjected to breeding. Breeding for intercropping aims at resource foraging traits of the admixed species to maximize niche complementarity, niche facilitation, and intercrop performance. The breeding process can be facilitated by modeling tools that simulate the outcome of the combination of different species' (or genotypes') traits for growth and yield development, reducing the need of extensive field testing. Here, we revisit the challenges associated with breeding for intercropping, and give an outlook on applying crop growth models to assist breeding for intercropping. We conclude that crop growth models can assist breeding for intercropping, provided that (i) they incorporate the relevant plant features and mechanisms driving interspecific plant-plant interactions; (ii) they are based on model parameters that are closely linked to the traits that breeders would select for; and (iii) model calibration and validation is done with field data measured in intercrops. Minimalist crop growth models are more likely to incorporate the above elements than comprehensive but parameter-intensive crop growth models. Their lower complexity and reduced parameter requirement facilitate the exploration of mechanisms at play and fulfil the model requirements for calibration of the appropriate crop growth models

Heat Waves and Broomrape Are the Major Constraints for Lentil Cultivation in Southern Spain

There is potential for expanding lentil cultivation to dry and warm Mediterranean rain-fed environments at low altitudes, where early sowings are recommended to profit from winter rains and escape drought and excessive heat at the grain filling stage. In cooler areas, frost might be a problem in the early sowings, however, in warmer areas such as our low altitude warm southern Spanish environments the most detrimental factor on lentil seed yield appeared to be high temperatures at grain-filling stage, particularly heat waves of more than 5 days with Tmax > 30 ◦C. This was followed by broomrape infection, the combination of both being dramatic. We detected variation for stress tolerance, with S17 and R7 accessions outstanding for all stress indexes used, followed by S23, Nsir, S6, and S12. Broomrape infection ranked second risk in the area. No complete resistance to broomrape was identified, but there was a significant variation in the level of infection, with accessions S14 and R17 being the more resistant across environments. This offers prospects for combining heat tolerance and broomrape resistance by breedingThis research was funded by the Junta de Andalucía grant P20_00986 and to Agencia Española de Investigación (AEI) grant PID2020-11468RB-100. Authors are deeply indebted to ICARDA for providing nurseries from which the studied accessions were selecte

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

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.Authors are greatly indebted to European Union projects FP7-ARIMNet-Medileg and FP7-LEGATO (grant agreement 613551) for financial support.Peer reviewedPeer Reviewe

Differences in crenate broomrape parasitism dynamics on three legume crops using a thermal time model

Root parasitic weeds are a major limiting production factor in a number of crops, and control is difficult. Genetic resistance and chemical control lead the fight, but without unequivocal success. Models that help to describe and even predict the evolution of parasitism underground are a valuable tool for herbicide applications, and even could help in breeding programs. Legumes are heavily affected by Orobanche crenata (crenate broomrape) in the Mediterranean basin. This work presents a descriptive model based on thermal time and correlating growing degree days (GDD) with the different developmental stages of the parasite. The model was developed in three different legume crops (faba bean, grass pea and lentil) attacked by crenate broomrape. The developmental stages of the parasite strongly correlated with the GDD and differences were found depending on the host crop. [This Document is Protected by copyright and was first published by Frontiers. All rights reserved. it is reproduced with permission.

Orobanche L. (Orobanchaceae) sect. Trionychon Wallr., en Andalucía II: Orobanche rosmarina Beck.

RESUMEN. Orobanche L. (Orobanchaceae) sect. Trionychon Wallr., en Andalucía II: Orobanche rosmarina Beck. Se indica la presencia de Orobanche rosmarina Beck en Andalucía. Aportamos la descripción de los ejemplares andaluces, su corología y habitat. Se incluyen unas nuevas claves de determinación para las especies andaluzas de la sect Trionychon.Palabras clave. Orobanchaceae, Orobanche, jopo, parásito, Andalucía.ABSTRACT. Orobanche L. (Orobanchaceae) sect. Trionychon Wallr., in Andalusia II: Orobanche rosmarina Beck. The presence of Orobanche rosmarina Beck in Andalusia is noted. Description, chorology and habitat of the Andalusian specimens is given. New identification keys are added.Key words. Orobanchaceae, Orobanche, broomrape, parasite, Andalusia