Body Rot Research Articles

Rootstocks influence ‘Hass’ avocado fruit quality and fruit minerals

SummaryTo determine the potential for rootstocks to improve avocado quality, ‘Hass’ fruit from trees on seedling ‘Velvick’ (SV), clonal ‘Velvick’ (CV) or clonal ‘Duke 7’ (CD) rootstocks were harvested in 1999 and 2000, ripened at 20°C immediately after harvest (non-stored) or stored at 5°C for four weeks (stored), and then fruit quality and mineral concentrations determined. In 2000, non-stored CV fruit had lower severity of body rots (5% of flesh volume affected, caused mainly by Colletotrichum gloeosporioides) than CD fruit (20%), while body rots severity in stored CV fruit was 20% compared with 38% in stored CD fruit. Stored CV fruit had less severe diffuse discoloration (3% and 9% in 1999 and 2000, respectively) than CD fruit (7% and 20%, respectively). Stored CV fruit also had less severe vascular browning (19%) than CD fruit (33%) in 2000. In both seasons, CV fruit had 15–19% higher flesh calcium concentrations, 17–22% higher flesh boron concentrations, and 14–15% lower flesh nitrogen concentrations than CD fruit. In 2000, CV fruit also had 27% more skin calcium and 14% less skin nitrogen than CD fruit. There were no effects of rootstock on yield, canopy volume, measured length of non-suberized roots, average fruit weight, fruit length: width ratio, skin thickness, dry matter, proportion of the fruit skin purple-black when ripe, or seed mass: fruit weight ratio. These results suggest that there is potential to improve ‘Hass’ avocado quality through rootstock selection, and that tree and fruit mineral concentrations have a role in this relationship.

The effect of low temperatures on Colletotrichum acutatum and Colletotrichum gloeosporioides causing body rots of avocados in New Zealand

The effect of extended periods at low temperatures on spore germination, survival and appressorial formation in Colletotrichum acutatum and C. gloeosporioides, and on pre-formed appressoria of C. gloeosporioides, was studied on water agar on glass slides on a temperature gradient plate. C. acutatum was more tolerant of low temperatures than was C. gloeosporioides. The addition of peptone to simulate endogenous nutrients on the avocado fruit surface affected spore germination and survival only slightly, and the effect was not statistically significant. These trends in vitro were also apparent in isolations from fruit rots. Infections by C. acutatum were not reduced by storage at 5.5°C before ripening. Incidence of infections caused by C. gloeosporioides was significantly fewer in fruit coolstored at 5.5°C for 30 days prior to ripening at 20°C than in fruit stored at 20°C. In the two lines of fruit studied, coolstorage reduced body rots in one line but not the other. The rots on the line of fruit not affected by coolstorage were mainly caused by C. acutatum. These results suggest that in coolstored fruit, the reduction in incidence of rots caused by C. gloeosporioides, but not of rots caused by the closely related fungus C. acutatum, was due to the greater sensitivity of spores of C. gloeosporioides to cold temperatures. Survival of pre-formed appressoria of C. gloeosporioides was not affected by temperatures used for coolstorage of avocados.

Low temperature conditioning before cold disinfestation improves ‘Hass’ avocado fruit quality

Abstract The potential for low temperature conditioning (LTC) treatments, either alone or in combination with hot water treatment (HWT), to improve the quality of ‘Hass’ avocado ( Persea americana Mill.) fruit following cold disinfestation of Queensland fruit flies, was investigated. Avocado fruit were held at 4–8 °C for 3–4 days then disinfested for 16 days at 1 °C before ripening at 16 °C. In a second experiment, fruit were placed in water at 41–42 °C for 15–25 min, either with or without LTC, then disinfested and ripened. In both experiments, LTC at 4 °C for 4 days or at 6–8 °C for 3–4 days increased the percentage of fruit with acceptable external appearance (less than 5% of the fruit with discrete dark patches on the skin, and skin spotting combined) after disinfestation from 0 to 100% due to the effective elimination of discrete patches on the skin. Disinfestation alone increased body rots and diffuse flesh discolouration severity in ripe fruit, while LTC before disinfestation reduced severity of these disorders to similar levels as those in non-disinfested, non-stored fruit. LTC before disinfestation reduced discrete patches severity and improved flesh quality more than HWT. Combined treatments of HWT and LTC before disinfestation were no more beneficial compared with LTC alone. Conditioning of fruit at 6 °C for 3 days followed by disinfestation resulted in no survivors from 50 748 third instars of Queensland fruit fly ( Bactrocera tryoni Froggatt). LTC efficacy was verified commercially by conditioning fruit at 6 °C for 3 days followed by disinfestation and airfreight to New Zealand. External fruit appearance and internal ripe fruit quality after disinfestation were found to be high. These results show that LTC before cold disinfestation effectively eliminates skin damage and improves flesh quality of ripe ‘Hass’ avocado fruit, with no negative effect on Queensland fruit fly disinfestation efficacy.

Hot water treatments improve ‘Hass’ avocado fruit quality after cold disinfestation

Abstract The potential for hot water treatment (HWT) to improve quality of ‘Hass’ avocado following cold disinfestation for fruit flies, was investigated. Avocado fruit were placed in water at 38–42 °C for 20–60 min, disinfested for 16 days at 1 °C, then ripened at 20 °C. In the following season, fruit from another orchard were treated with hot water at 39–42 °C for 20–30 min, disinfested as above, then ripened at 16 °C. In both seasons, HWT significantly reduced skin damage caused by cold disinfestation, with 40 °C for 30 min, 41 °C for 20–30 min and 42 °C for 25–30 min giving the greatest reduction. Hot water treatments also reduced body rots in ripe fruit, with 40 and 41 °C for 30 min being consistently the most effective. Treatment at 42 °C increased body rots compared to the other HWTs in one season, and there was no benefit of HWT times longer than 30 min. The severity of vascular browning (VB) and mesocarp discolouration (MD) in ripe fruit was generally low, and increased following cold disinfestation. Hot water treatments reduced VB severity but had no effect on MD. Treatment at 41 °C for 25–30 min and 42 °C for 25 min increased the percentage of externally acceptable fruit (less than 5% of the skin area with defects) from 0 to about 80% 3 days after removal from disinfestation. The same treatment also increased the percentage of ripe fruit with acceptable flesh quality (less than 5% of the flesh with rots or disorders) from 0 to 16–20%, due mainly to reduced body rots. These results indicate the commercial potential of HWTs of about 41 °C for 25–30 min, or 42 °C for 25 min to improve avocado external and internal fruit quality following cold disinfestation.

Percentage of Dry Matter and Oil Content Are Not Reliable Indicators of Fruit Maturity or Quality in Late-harvested `Hass' Avocado

The potential to use percentage of dry matter (DM) and/or oil of the flesh of `Hass' avocado as a maturity standard to determine the latest harvest for acceptable fruit quality, was investigated. `Hass' avocado fruit were harvested from early October to mid-January from a commercial orchard in subtropical Queensland. The percentage of DM and oil changed little during the harvest period, and the eating quality of the flesh remained high. However, the incidence of body rots (caused mainly by Colletotrichum sp.) and the flesh disorders grey pulp and vascular browning, increased with harvest. These results indicate that percentage of DM and oil are not reliable late-maturity standards because of the inconsistent change with later harvests, and that disease and internal disorders can be the main determinants of latest acceptable harvest, rather than eating quality.

Nature, Nurture, and Memory in a Socialist Utopia: Delineating the Soviet Socio-Ethnic Body in the Age of Socialism

Therefore as soon as a spark appears it must be snuffed out, and the yeast separated from the vicinity of the dough, the rancid flesh cut off, and the mangy animal driven away from the flock of sheep, lest the entire house burn, the dough spoil, the body rot, and the flock perish. [The heretic] Arius was one spark in Alexandria; but because he was not immediately suppressed, the entire world was devastated with his flame.

Pretreatments at 38 °C of `Hass' Avocado Confer Thermotolerance to 50 °C Hot Water Treatments

`Hass' avocados [Persea americana Mill.] were pretreated in water (38 °C for up to 120 min) immediately before 50 °C hot water treatments of up to 10 min. Fruit were stored for 1 week at 6 °C and ripened at 20 °C. External browning was evaluated immediately upon removal from cold storage, and fruit quality evaluated when fruit were ripe. Pretreatments at 38 °C tended to reduce the levels of external browning, skin hardening, and internal disorders, such as tissue breakdown and body rots, that were associated, and increased, with longer hot water treatments. A pretreatment of 60 min was the most effective for eliminating external browning, and reducing hardening of the skin when fruit were ripe following hot water treatment. Examination of heat shock protein (hsp) gene expression in avocado skin tissue, showed that levels of hspl7 and hsp70 homologous mRNA increased with increasing pretreatment duration. The results demonstrate that 38 °C pretreatments increase the tolerance of avocado fruit to subsequent hot water treatments.

Production locality affects mango fruit quality

Summary. Differences in mango (cv. Kensington Pride) fruit quality under commercial and research conditions have been frequently noted. To assess the potential for production conditions to influence fruit quality, "Kensington Pride" mango fruit were obtained from 2 adjacent sites on an orchard on shallow nodular yellow podsolic soil in tropical North Queensland, 1 block of trees growing on soil with river gravel (site 1) and another without gravel (site 2). Fruit were also obtained from trees on a gleyed podsolic soil (site 3) in subtropical south-east Queensland. Fruit were harvested weekly for 4 weeks, with quality determined after ripening at 22°C and after storage at 10°C for 4 weeks. Eating quality and percentage dry matter increased, while days to eating soft decreased with later harvests. Fruit from site 3 (cooler growing conditions, rain during the harvest period) had acceptable eating quality at a lower dry matter than fruit from sites 1 and 2. The percentage of green colour on the skin (GS) at ripe was higher at harvest 2 in fruit from sites 1 and 2, but was lower at harvest 4 in fruit from all sites. Disease severity in fruit ripened without storage was higher in site 3 fruit, while body rots (caused mainly by Colletotrichum spp.) increased (site 3 only) and stem end rots (caused mainly by Dothiorella spp.) decreased with later harvests. Fruit firmness and GS decreased during storage at 10°C, but fruit from site 3 were generally softer, with higher GS, than those from the other sites. Chilling injury was also higher in fruit from site 3.

Growth interactions betweenPleurotus tuber-regium andSclerotium rolfsii

Sclerotium rolfsii, a destructive soil pathogen common in tropical soils, was found to cause stipe rot of the fruit bodies ofPleurotus tuber-regium. The rot occurs only when the pathogen is inoculated into the soil before seeding and before primordial emergence. It caused 100% inhibition of primordia and sporophore formation when the soil was inoculated before seeding and highly reduced yield when the soil was inoculated with the pathogen just before primordial emergence. However, no fruit body rot occurred on the mushroom when the soil was inoculated with the pathogen after primordial emergence from the soil.