Unlike ACS and ACO1, SlCBF1 showed a clear spatial differentiation in both chilling and control conditions. Expression was higher in the pericarp compared to the columella , which suggests that the former might be more responsive to cold stress, possibly due to its external localization. Under chilling in both tissues, SlCBF1 expression peaked at 1h and was sustained for 24h in our study, which can be described as an early response , it then declined to the levels observed at the control temperature, after 3 weeks cold treatment. In other studies, cold storage induced expression of SlCBF1 for up to 8h; 8 days, and 14 days, however there was no induction at 6 °C in Micro-Tom fruit. Te upregulation of SlCBF1 may therefore be dependent on fruit developmental stage, the severity of cold stress, and genotype. After rewarming of the ‘control fruit’, SlCBF1 expression increased to levels higher than during chilling . This may be suggestive of two things: first, that SlCBF1 transcripts in chilled tissues were unable to reach the same levels as tissue held in control temperature, since they were developmentally repressed; and second, SlCBF1 is involved in ripening independent of ACO1 or ACS2, given the asynchrony of their expression . However, a correlation between endogenous ethylene production and SlCBF1 upregulation could partly explain this behavior and matches our observations . Dehydration stress response. Dehydrins , are protective proteins that accumulate in response to dehydration-associated stresses, including chilling. The expression of the clone FC11CA08-2, here named DHN, was analyzed in this study. DHN mRNA levels increased only after 24 h and 3w of post harvest chilling inthe pericarp, drainage collection pot or 3w in the columella with decreases in both tissues after rewarming. There were no detectable differences between tissues, however they responded differentially to temperature .

After rewarming, ‘control pericarp’ DHN expression was higher than that in the ‘chilled pericarp’, due to ripening taking place in the control. It appears that DHN transcript abundance in fruit increases as ripening progresses. The magnitude of changes were greater at 2.5 °C compared to 12.5 °C, consistent with a higher requirement for the molecular chaperones encoded under cold-stress. Oxidative damage. Prolonged or intense chilling stress induces ROS overproduction, which accelerates cell death. The alternative oxidase pathway is activated to minimize ROS levels, and in tomato fruit, AOX1a has been associated with enhanced PCI tolerance. Therefore, AOX1a was studied here. Lipoxygenases catalyze the peroxidation of polyunsaturated fatty acids and are associated with both ripening and redox balance, processes affected by PCI. The expression of the LoxB isoform has not been studied during fruit post harvest chilling storage, and was included. AOX1a expression levels in pericarp and columella were similar, but chilling induced a differential response over time. Transcript levels in the pericarp peaked at 24h and 3w, similar to that seen by Fung et al.. The ‘chilled pericarp’ had a reduced AOX1a expression after rewarming while the ‘chilled columella’ changed little even after rewarming. Under control conditions in both tissues, gradual increases were observed, but rewarming enhanced AOX1a expression , matching ethylene production rates , consistent with ethylene regulation of this gene. ACO1, ACS2 and AOX1a, were co-expressed, but chilling suppressed this correlation . PCI therefore contributes to the uncoupling of ripening-related ethylene biosynthesis, highlighted by the inability of chilled tomato to resume normal ripening after rewarming . LoxB expression displayed a mixed spatial-response that varied with temperature. Expression in both pericarp and columella was unchanged at 1h and 24h .

After 3 weeks, expression was down regulated, but in contrast, rewarming induced the upregulation of LoxB in both tissues. LoxB expression matched ethylene production, consistent with its regulation by this hormone. LoxB expression also paralleled MDA values after rewarming in the columella , in agreement with membrane alterations induced by PCI. The correlation of LoxB with ethylene production rates and ripening was in accordance with the strong correlation between LoxB and ACS2 at 12.5 °C . Interestingly, transcript levels in the ‘control pericarp’ plus rewarming were higher than those of rewarmed tissue after chilling, even though ethylene levels were 1.2-fold higher in the latter. In this case, ethylene production increased in response to chilling-induced stress and not due to ongoing ripening.Principal Component Analysis was performed to explore the structure of the gene expression data from a spatial perspective with respect to cold storage and rewarming of chilled tissue . The first and second principal components explained 75 and 15% of the variation present in the data, respectively. Data for the pericarp and columella portions under chilling for 3 weeks separated from the rewarmed tissues. More importantly, the data distinguished among tissues, with the pericarp and columella showing a clear separation even though gene expression differences between cold and rewarming were a greater determinant of the patterns seen on the PCA. Overall this analysis supports the hypothesis of a spatial and temporal differentiation in response to chilling stress at the gene expression level.Post harvest chilling injury is a complex multifactorial disorder with detrimental effects on tomato fruit quality and shelf-life. With the aim of representing the tomato fruit as a multilayered and integrated system of response to cold stress, we analyzed PCI impact on different fruit tissues and correlated it with known physiological parameters .

Overall, cold stress uncoupled key molecular, biochemical, and physiological processes occurring during the normal progression of storage and ripening. Increased water mobility and tissue liquefaction were also disrupted as evidenced by MRI-obtained D-values from the pericarp, columella and locular portions, and ion leakage obtained from the pericarp. MRI and color development confirmed three concepts: first, the system’s inability to restore or repair the chilling-affected mechanisms; second, that PCI is cumulative and progressive over time; and third, the need to examine each tissue to characterize PCI’s progression and symptomatology, since the most studied fraction, the pericarp, may not reflect processes occurring in other tissues. Reduced starch breakdown in columella and seed discoloration during cold storage reflect that, besides external changes, PCI extends to internal tissues. Tissues exhibited heterogeneous patterns of response to PCI at the biophysical, biochemical and molecular levels. D-values were intrinsically different in the three tissues under study, and their time evolution and temperature responses were also mixed. Responses to oxidative damage represented by the lipid peroxidation byproduct MDA varied in response to temperature but peaked after rewarming, which again highlights that after crossing a threshold of cumulative cold damage, rewarming aggravates PCI’s manifestation instead of alleviating it. Starch accumulation also showed significant spatial differences, suggesting that tissues may display a sharper specialization at the metabolite than at other levels. Responses to cold from the perspective of gene expression were highly dependent on the tissue-type, temperature and time of storage, but overall, they paralleled ethylene production trends via stress response or ripening. Some genes seemed to act concertedly across experimental conditions , others acted coordinately under either cold or control conditions or under apparently independent programs . Transcript accumulation was higher in the pericarp across conditions , square plastic pot equally expressed in both tissues , or, dependent on temperature and storage time . Taken together, this evidence reveals the dynamism of cold-stress in the tomato system and suggests that fruit may display specialized mechanisms to elaborate a response to this environmental challenge. It also unfolds numerous questions about the nature of such varied responses among fruit tissues: are they advantageous to the fruit under stress? What is the source of these differences? Would such relationships differ in the fruit from cold-tolerant tomato species? Exploring these questions in a comprehensive way may deepen our knowledge of this complex phenomenon to elaborate long-term, robust solutions.The efficacy and palatability of commercially available rodenticides can vary greatly, and bait effectiveness is often specific to particular pest species . Many rodenticides have been developed to control rodent populations , and several studies have assessed the materials’ ability to control rats and mice in natural areas . However, until now no peer-reviewed studies had tested the efficacy of rodenticides for roof rat control in nut or tree fruit crops, and few if any studies had been conducted on deer mice. We recently initiated an investigation into the efficacy of three rodenticide baits for control of roof rat and deer mouse activity in almond orchards and found that the 0.005% diphacinone oat bait, sold in many county Agricultural Commissioner’s offices, was highly effective . This study made use of elevated bait stations, which proved effective at supplying bait to target species while substantially limiting access to rodenticides for many non-target species. In this publication we provide information on how to identify damage from roof rats and deer mice in nut and tree fruit orchards, and how to effectively implement a baiting program to control these pests. This appears to be an efficacious, cost-effective, and safe baiting protocol for control of roof rats and deer mice in orchard crops, something that has thus far been unavailable to growers.Accurate identification of the species responsible for damage is essential to development of an effective pest management program. If your management plan focuses on the wrong species, it is likely to be ineffective and it may pose hazards to non-target species and even be an illegal misuse of the material, based on the rodenticide label information.

Fortunately, the presence of roof rats and deer mice can often be detected through indirect monitoring techniques. For example, roof rats often burrow at the bottom of trees, and these burrows are typically 2 to 3 inches in diameter . Burrows of the California ground squirrel are sometimes this same size, but usually they are a bit larger . Also, if ground squirrels are present, you will see them running around above ground and hanging out in burrows.Discarded almond shells at the entrance of a burrow can help you determine the depredating species , but distinguishing between damage from deer mice and roof rats can be difficult. Deer mouse burrow openings typically average around 1.5 inches in diameter. If burrow openings of this size are present, the depredating species may be the deer mouse. Vole and deer mouse burrow openings are similar in size, but voles are not typically found in almond orchards, so long as ground cover is limited. If burrow openings are larger , the roof rat is the likely culprit.he bait stations used in our field trials were tubular structures manufactured specifically for Orange County Vector Control . The bait station consisted of high-density polyethylene plastic tubes that were 13 in long and 3.94 in inside diameter . A steel end cap was fixed onto each end of the tube. Each end cap was penetrated with a 1.89-in opening, big enough to allow the roof rats and deer mice to enter the station and small enough to reduce or even eliminate any inadvertent loss of bait from the bait station. On the inside of the metal cap, under the opening, a 4.5-in long metal shelf is present. This also helps reduce bait loss. As of this writing, these bait stations are available for sale in a limited supply from the Los Angeles County Agricultural Commissioner’s office. We are exploring additional supply options.The current label for 0.005% diphacinone oat bait only allows baiting during the non-bearing season. This means that growers need to be proactive when dealing with rodent infestations. It is the responsibility of the grower to be aware of the presence of endangered species in orchards where they intend to implement a control program, since the bait may prove hazardous to non-target species. The killing of an endangered species may result in a fine and imprisonment under the Endangered Species Act 1973. The use of elevated bait stations will eliminate access to bait for many protected mammal species, such as kangaroo rats . Although other protected species, such as the Tulare grasshopper mouse , are not usually associated with climbing trees, growers must be vigilant in areas where these and other protected species are found. Growers can consult the California Department of Pesticide Regulations PRESCRIBE website for any endangered species restrictions associated with bait application. We recommend placing bait stations either 98 feet or 164 feet from each other, throughout the orchard.