Sources of vase life variation in cut roses: A review

n determining vase life (VL), it is often not considered that the measured VL in a particular experiment may greatly depend on both the preharvest and evaluation environmental conditions. This makes the comparison between studies difficult and may lead to erroneous interpretation of results. In this review, we critically discuss the effect of the growth environment on the VL of cut roses. This effect is mainly related to changes in stomatal responsiveness, regulating water loss, whereas cut flower carbohydrate status appears less critical. When comparing cultivars, postharvest water loss and VL often show no correlation, indicating that components such as variation in the tissue resistance to cavitate and/or collapse at low water potential play an important role in the incidence of water stress symptoms. The effect of the growth environment on these components remains unknown. Botrytis cinerea sporulation and infection, as well as cut rose susceptibility to the pathogen are also affected by the growth environment, with the latter being largely unexplored. A huge variability in the choices made with respect to the experimental setup (harvest/conditioning methods, test room conditions and VL terminating symptoms) is reported. We highlight that these decisions, though frequently overlooked, influence the outcome of the study. Specifications for each of these factors are proposed as necessary to achieve a common VL protocol. Documentation of both preharvest conditions and a number of postharvest factors, including the test room conditions, is recommended not only for assisting comparisons between studies, but also to identify factors with major effects on VL.

Two distinct classes of QTL determine rust resistance in sorghum

Background: Agriculture is facing enormous challenges to feed a growing population in the face of rapidly evolving pests and pathogens. The rusts, in particular, are a major pathogen of cereal crops with the potential to cause large reductions in yield. Improving stable disease resistance is an on-going major and challenging focus for many plant breeding programs, due to the rapidly evolving nature of the pathogen. Sorghum is a major summer cereal crop that is also a host for a rust pathogen which occurs in almost all sorghum growing areas of the world, causing direct and indirect yield losses in sorghum worldwide, however knowledge about its genetic control is still limited. In order to further investigate this issue, QTL and association mapping methods were implemented to study rust resistance in three bi-parental populations and an association mapping set of elite breeding lines in different environments. Results: In total, 64 significant or highly significant QTL and 21 suggestive rust resistance QTL were identified representing 55 unique genomic regions. Comparisons across populations within the current study and with rust QTL identified previously in both sorghum and maize revealed a high degree of correspondence in QTL location. Negative phenotypic correlations were observed between rust, maturity and height, indicating a trend for both early maturing and shorter genotypes to be more susceptible to rust. Conclusions: The significant amount of QTL co-location across traits, in addition to the consistency in the direction of QTL allele effects, has provided evidence to support pleiotropic QTL action across rust, height, maturity and stay-green, supporting the role of carbon stress in susceptibility to rust. Classical rust resistance QTL regions that did not co-locate with height, maturity or stay-green QTL were found to be significantly enriched for the defence-related NBS-encoding gene family, in contrast to the lack of defence-related gene enrichment in multi-trait effect rust resistance QTL. The distinction of disease resistance QTL hot-spots, enriched with defence-related gene families from QTL which impact on development and partitioning, provides plant breeders with knowledge which will allow for fast-tracking varieties with both durable pathogen resistance and appropriate adaptive traits.