Volatile Profile of Wall Rocket Baby-Leaves (Diplotaxis erucoides) Grown under Greenhouse: Main Compounds and Genotype Diversity

Wall rocket is a leafy vegetable with pungent flavor related to the presence of isothiocyanates (ITCs). Despite interest in it as a crop of high organoleptic quality, the variability of the volatile profile in the species remains unknown. Twenty-four populations grown under a greenhouse were evaluated. A considerable diversity for the total levels of volatiles was found, providing information of the aroma intensity among accessions. ITCs represented the main fraction. Allyl ITC was the main compound, and levels showed up to 6-fold difference among populations. The esters fraction was mainly represented by cis-3-hexenyl isovalerate and cis-3-hexenyl butyrate, with 20-fold differences among populations. Additionally, the content in sinigrin was evaluated as main GSL in wall rocket. Differences reached up to 13-fold. These results suggest that some populations can be used to develop highly pungent varieties, whereas some others can be selected for mild-pungent varieties, as it is the case of DER045 with low levels of ITCs and high in esters. The presence of several ITCs in the profile also suggested the presence of other novel GSLs. Overall, the work increases the knowledge in the variability of wall rocket for the volatile profile and sinigrin accumulation, a starting point for future breeding programs.

Target Site Resistance to Acetolactate Synthase Inhibitors in Diplotaxis erucoides and Erucaria hispanica–Mechanism of Resistance and Response to Alternative Herbicides

Diplotaxis erucoides and Erucaria hispanica are common weeds of the Mediterranean region; they infest various habitats including cultivated fields and roadsides. In several fields across Israel, farmers have reported on poor control of D. erucoides and E. hispanica plants using acetolactate synthase (ALS) inhibitors. Greenhouse experiments were conducted to determine the effect of various ALS inhibitors on plants from two potentially resistant D. erucoides and E. hispanica populations. Additionally, alternative management strategies using auxinic herbicides were studied. Plants from both populations exhibited resistance to all tested ALS inhibitors, up to 20-fold the label field rate, as compared with ALS sensitive populations of D. erucoides and E. hispanica. Sequencing of the ALS gene revealed Trp574 to Leu substitution in ALS-resistant D. erucoides plants, whereas a Pro197 to Ser substitution was detected in ALS-resistant E. hispanica plants. Although high levels of resistance were observed in individuals from both putative resistant populations, sensitive individuals were also detected, suggesting the evolution of resistance in these two populations is still in progress. Auxinic herbicides, 2,4-D, and mecoprop-P, provided excellent control of plants from both ALS-resistant populations. This study documents and confirms the first case of evolution of resistance to ALS inhibitors in D. erucoides and E. hispanica populations.

Morphological Diversity and Bioactive Compounds in Wall Rocket (Diplotaxis erucoides (L.) DC.)

Wall rocket is a wild vegetable with interest to become a crop. However, the information regarding morphological variability in the species is scarce, despite the interest it has received for breeding programs. In addition, evaluating the phytochemical composition can also be useful for developing materials of a high quality. In this study, forty-four populations were evaluated for selected morphoagronomic traits and contents in ascorbic acid (AA), total phenolics (TP), and nitrates (NO3−). Wall rocket plants had, on average, an intermediate growth habit and a good response to transplant. Moderate variability, mainly for size-related traits, was found, with low to moderate heritability estimates (H2 < 0.35). A Principal Component Analysis revealed that some materials may be selected for differenced traits. On the other hand, wall rocket materials had, on average, high contents in AA (53 mg 100 g−1) and TP (116 mg CAE 100 g−1) but also accumulated high levels of NO3− (891 mg 100 g−1). Significant positive correlations were found for AA and TP, which could be exploited for increasing the antioxidant activity and properties of the final product. We provide new information on the variation of wall rocket for traits of morphological and phytochemical interest, which together with other traits, such as the profile of glucosinolates, can be useful for the selection of materials in future breeding programs.

Growing Conditions Affect the Phytochemical Composition of Edible Wall Rocket (Diplotaxis erucoides)

Wall rocket (Diplotaxis erucoides) is a wild vegetable with the potential to become a crop of high antioxidant quality. The main bioactive compounds include ascorbic acid (AA), sinigrin, and a high content of total phenolic compounds (TP). It also accumulates nitrates. Since these compounds are affected by environmental conditions, adequate crop management may enhance its quality. Eleven accessions of wall rocket were evaluated under field and greenhouse conditions during two cycles (winter and spring) and compared to Eruca sativa and Diplotaxis tenuifolia crops. The three species did not differ greatly. As an exception, sinigrin was only identified in wall rocket. For the within-species analysis, the results revealed a high effect of the growing system, but this was low among accessions. The highest contents of AA and TP were obtained under field conditions. In addition, the levels of nitrates were lower in this system. A negative correlation between nitrates and antioxidants was determined. As a counterpart, cultivation in the field–winter environment significantly decreased the percentage of humidity (87%). These results are of relevance for the adaptation of wall rocket to different growing conditions and suggest that the field system enhances its quality. The low genotypic differences suggest that intra-species selections in breeding programs may consider other aspects with greater variation.