Future opportunities for crop physiology in fruit production

This paper outlines some of the challenges and opportunities for whole plant and crop physiologists to contribute to enhanced and more efficient fruit production in the coming years. The rapid advances in molecular biology provide both an opportunity (especially to improve understanding of physiological processes in crop production) and a challenge (to use this knowledge to advance production in real farm situations). Similar or even greater opportunities are being provided by other developing technologies, especially the rapidly increasing power and availability of powerful computing and communications technology and smartphones which provide real opportunities to contribute to improved crop and farm management. In addition the rapid development of novel 'remote' or 'proximal' sensing technologies, including the use of unmanned aerial vehicles and on-tractor sensors for crop monitoring and stress diagnosis also holds great promise. These and other advances are discussed in the context of their potential for improving both crop breeding and orchard management, drawing on examples from a wide range of crops. The potential of these scientific advances will be put in the context of other factors relating to the advance of horticultural knowledge including the availability of funding and the training of young scientists.</p

The tomato SlIAA15 is involved in trichome formation and axillary shoot development

The Aux/IAA genes encode a large family of short-lived proteins known to regulate auxin signalling in plants. Functional characterization of SlIAA15, a member of the tomato (Solanum lycopersicum) Aux/IAA family, shows that the encoded protein acts as a strong repressor of auxin-dependent transcription. The physiological significance of SlIAA15 was addressed by a reverse genetics approach, revealing that SlIAA15 plays multiple roles in plant developmental processes. The SlIAA15 down-regulated lines display lower trichome number, reduced apical dominance with associated modified pattern of axillary shoot development, increased lateral root formation and decreased fruit set. Moreover, the leaves of SlIAA15-inhibited plants are dark green and thick, with larger pavement cells, longer palisade cells and larger intercellular space of spongy mesophyll cells. The SlIAA15-suppressed plants exhibit a strong reduction in type I, V and VI trichome formation, suggesting that auxin-dependent transcriptional regulation is required for trichome initiation. Concomitant with reduced trichome formation, the expression of some R2R3 MYB genes, putatively involved in the control of trichome differentiation, is altered. These phenotypes uncover novel and specialized roles for Aux/IAAs in plant developmental processes, clearly indicating that members of the Aux/IAA gene family in tomato perform both overlapping and specific functions

Distortion of trichome morphology by the hairless mutation of tomato affects leaf surface chemistry

Trichomes are specialized epidermal structures that function as physical and chemical deterrents against arthropod herbivores. Aerial tissues of cultivated tomato (Solanum lycopersicum) are populated by several morphologically distinct trichome types, the most abundant of which is the type VI glandular trichome that produces various specialized metabolites. Here, the effect of the hairless (hl) mutation on trichome density and morphology, chemical composition, and resistance to a natural insect herbivore of tomato was investigated. The results show that the major effect of hl on pubescence results from structural distortion (bending and swelling) of all trichome types in aerial tissues. Leaf surface extracts and isolated type VI glands from hl plants contained wild-type levels of monoterpenes, glycoalkaloids, and acyl sugars, but were deficient in sesquiterpene and polyphenolic compounds implicated in anti-insect defence. No-choice bioassays showed that hl plants are compromised in resistance to the specialist herbivore Manduca sexta. These results establish a link between the morphology and chemical composition of glandular trichomes in cultivated tomato, and show that hl-mediated changes in these leaf surface traits correlate with decreased resistance to insect herbivory

Growth regulation in top fruit

Growth regulators offer possibilities of compensating for genotypic deficiencies that, in top fruit, would take many years to alter by genetical methods and, in marginal climates, they can help to overcome environmental shortcomings such as spring frosts or lack of winter chilling. In addition to their use in the control of growth and fruiting, they have made possible the development of advanced experimental systems in which pruning and harvesting may be fully mechanized. </jats:p