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Sunflower, a relevant crop for oil production in temperature regions, is subjected to various biotic stresses. Significance of a particular stress agent, both spatially and temporally, is determined by the environmental limitations and the pest population variability. This chapter provides a review of the major sunflower diseases and pests, with an emphasis on their distribution and description of the damage they may cause. Besides, we discuss different strategies used in sunflower breeding for biotic stress resistance, strategy that is reliable, durable, cost effective and with low negative impact on environment, for pest and disease control. During a long history of sunflower cultivation, several major breakthroughs in breeding for resistance to diseases and pests were made. Recent breakthrough in sunflower genomics and availability of genome data of both sunflower and its pathogens opens up the new possibilities for introduction of biotic stress resistance into cultivated sunflower. In the light of changes made over the history and the recent findings we discuss new tools available for designing sunflower crop resilient to biotic stresses.

Sunflower, a relevant crop for oil production in temperature regions, is subjected to various biotic stresses. Significance of a particular stress agent, both spatially and temporally, is determined by the environmental limitations and the pest population variability. This chapter provides a review of the major sunflower diseases and pests, with an emphasis on their distribution and description of the damage they may cause. Besides, we discuss different strategies used in sunflower breeding for biotic stress resistance, strategy that is reliable, durable, cost effective and with low negative impact on environment, for pest and disease control. During a long history of sunflower cultivation, several major breakthroughs in breeding for resistance to diseases and pests were made. Recent breakthrough in sunflower genomics and availability of genome data of both sunflower and its pathogens opens up the new possibilities for introduction of biotic stress resistance into cultivated sunflower. In the light of changes made over the history and the recent findings we discuss new tools available for designing sunflower crop resilient to biotic stresses.

Verticillium wilt of olive (VWO), caused by the soil-borne pathogen Verticillium dahliae, is considered one of the most important diseases affecting this tree crop. One of the best VWO management measures is the use of tolerant cultivars. Remarkably, no information is available about olive functional traits and their potential relationship with tolerance to V. dahliae. Twenty-five selected functional traits (for leaf, stem, root and whole plant) were evaluated in six olive varieties differing in their VWO tolerance level to identify possible links between this phenotype and functional traits’ variation. High intervarietal diversity was found among cultivars and several functional traits were related with VWO tolerance. Tolerant varieties showed higher leaf area, dry matter content (leaf, stem and plant) and mass fraction for stems, but lower for leaves. Significant differences were also detected for root functional traits, tolerant cultivars displaying larger fine root diameter and lignin content but smaller specific length and area of thick and fine roots. Correlations were found among functional traits both within varieties and between levels of tolerance/susceptibility to VWO. Associations were observed between biomass allocation, dry matter content and VWO tolerance. The most relevant difference between tolerant and susceptible cultivars was related to root system architecture.

Verticillium (Verticillium dahliae Kleb.) wilt is one of the most devastating diseases affecting olive (Olea europaea L. subsp. europaea var. europaea) cultivation. Its effective control strongly relies on integrated management strategies. Olive cultivation systems are experiencing important changes (e.g., high-density orchards, etc.) aiming at improving productivity. The impact of these changes on soil biology and the incidence/severity of olive pests and diseases has not yet been sufficiently evaluated. A comprehensive understanding of the biology of the pathogen and its populations, the epidemiological factors contributing to exacerbating the disease, the underlying mechanisms of tolerance/resistance, and the involvement of the olive-associated microbiota in the tree’s health is needed. This knowledge will be instrumental to developing more effective control measures to confront the disease in regions where the pathogen is present, or to exclude it from V. dahliae-free areas. This review compiles the most recent advances achieved to understand the olive–V. dahliae interaction as well as measures to control the disease. Aspects such as the molecular basis of the host–pathogen interaction, the identification of new biocontrol agents, the implementation of “-omics” approaches to unravel the basis of disease tolerance, and the utilization of remote sensing technology for the early detection of pathogen attacks are highlighted.

Broomrape (Orobanche cumana Wallr.) is one of the most important constraints on sunflower production in Europe and Asia. It produces a large number of small seeds that are easily disseminated, leading to the build-up of O. cumana populations, and the constant appearance of new, and more virulent races. Current racial situation of broomrape in the main infested areas is unclear, since there is a lack of information on whether races under the same name reported in different countries are the same or differ in terms of virulence. Among the several control options proposed, breeding for resistance have been found to be most effective and environmental friendly way. Since O. cumana resistance is broken frequently, multiple sources of resistance are needed to control the emerging races. In a line with this goal, the Institute of Field and Vegetable Crops Novi Sad has been testing the wild relatives of the sunflower (long-term program) as well as inbred lines in gene bank (short-term program) and identified sources that confer resistance to highly virulent races. Some resistance sources have been found to be controlled by major genes, some have recessive inheritance, but some showed QTL resistance. Race-specific dominant genes are considered as good sources of resistance, but emerging of new races increase the aggressiveness and breakdown vertical resistance. Therefore, pyramiding of more than one resistance gene from different sources into a single genotype would lead to the better ways of achieving durability of resistance. The complexity of host resistance has been also improved using molecular marker analyses for identifying and mapping resistance genes.

Broomrape (Orobanche cumana) is a parasitic weed that causes substantial yield losses in sunflower. While chemical options for suppressing sunflower broomrape are available, breeding for resistance has both economic and environmental advantages. In a previous study, we reported on the mapping of polygenic broomrape resistance in the HA-267xOD-DI-82 mapping population. We identified 2 major quantitative trait loci (QTL), or7.1 and or12.1, as well as numerous small effect QTLs that were dispersed across the genome. While these results provided valuable insights into the complexity of resistance to broomrape, QTL validation is an important and often overlooked step for breeding. The aim of this study is to assess the effects of these QTLs in an unrelated genetic background and to identify QTLs that are stable and thus have the highest breeding value. To achieve this goal, resistant line HA-267 was crossed with a susceptible parental line HA-26-PR, and a mapping population consisting of 189 individuals was developed. Following phenotyping, we used selective bulked segregant analyses coupled with genotyping-by-sequencing (GBS) to re-map QTLs conferring resistance to broomrape population LP12BSR. A total of 7 QTLs were identified. The results confirmed that the effects of QTLs or7.1 and or12.1 was large and consistent. Importantly, an additional QTL located on sunflower chromosome 3 (or3.1), which was previously proven to control resistance to broomrape race E, appeared to have a larger effect in the new HA-267xHA-26-PR cross compared to the previous one (HA-267xOD-DI-82). These validated and stable QTLs will be prioritized in breeding, and associated molecular markers will facilitate marker-assisted selection.

Maize is arguably the most widely grown crop in the world, but it is often associated with one of its major insect pests, the European corn borer (ECB). The damage caused by this species to maize production is generally variable, but in many cases it is economically significant. This review paper provides an overview of the research findings on the natural plant defence mechanisms against ECB larvae published till now. What is resistance and how it is achieved, what is the chemical response of maize plants to insect feeding and how tolerance can be increased. A short introduction in breeding for resistance and a discussion if the mentioned traits can be used in conventional breeding in order to create maize hybrids less affected by ECB are given.

Breeding for resistance to forest pests and pathogens is emerging as a promising tool for minimising the impact of the increasing biotic threats that our forests are experiencing as a consequence of global change. Efficient phenotyping protocols of resistance are urgently needed. Here we present the results of two experiments aimed to determine whether the variation in resistance to the pine weevil Hylobius abietis, a harmful pest of European conifers, can be inferred by nondestructive bioassays using excised plant material collected in forest genetic trials. Weevil damage and amount of nonvolatile resin induced by weevil feeding were assessed in young trees and in branches of adult trees using several phenotyping procedures (bioassays using either living trees, excised plant material and cut stem twigs) on four pine species (Pinus pinaster, P. radiata, P. sylvestris and P. pinea). Half of the plants were previously induced with methyl jasmonate (MJ), a treatment that is known to affect resistance to the pine weevil. In Experiment 1, living and excised plants showed parallel results: MJ treatment significantly reduced weevil damage, and saplings responded to weevil damage locally increasing the nonvolatile resin (NVR) in the stems proportionally to the damage suffered. This response was, however, slightly lower in excised than in living saplings. On the contrary, patterns of weevil feeding on stem twigs completely departed from those observed in living and excised seedlings. Moreover, cut stem twigs were unable to respond to weevil feeding increasing NVR according to the weevil damage. In Experiment 2, assessment of weevil damage on excised branches explained around 50% of variation in damage on living branches. This relationship became much more pronounced (R2 = 0.81) when explored at the mean treatment level; branch manipulation did not alter the patterns of variation in resistance across pine species or MJ treatments. Irrespective of the assessment procedure, MJ

Corn reddening (CR), observed for the first time in Serbia in 1957, has occurred sporadically there ever since, especially in the Banat area. However, in 2002 and 2003 severe outbreaks took place in late July-early August. Initial symptoms of CR consist in the apperance of a red-violet color on the leaves, leaf sheaths, husks and the bare portion of the internodes. Discolourations typically appear at the milk maturity stage, being strongest on top leaves, around the mid-rib and along the edges of the leaf blade, from base to tip. The ears are underdeveloped and kernels are shrivelled. Soon after symptom development, affected plants wilt, the foliage dessicates rapidly, most of the red pigmentation disappears, and affected plants eventually die. Controversy on the biotic or abiotic nature of CR seems to have been settled by the recent discovery of a possible phytoplasma aetiology. Whatever the cause, an interesting source of apparent resistance to CR was identified in a local maize population which may be used in breeding programmes.