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

RAPD and isozyme analysis of genetic relationships between Carica papaya and wild relatives

The genetic origin of cultivated papaya is not clear. Wild relatives of papaya (Carica papaya) from central southern America were investigated using isozyme and RAPD analysis. Seven other species (including six from the genus Carica) were found to be relatively distant from papaya providing no indication of the genetic origin of papaya. Isozyme and RAPD data gave similar measures of genetic similarity within this group. C. papaya was about 70% dissimilar to the other Carica species by both methods. The other Carica species had average dissimilarities around 50%. Two species, C. pubescens and C. stipulata were much closer to each other with similarities of 87% by isozyme analysis and 82% by RAPD analysis. Although both methods gave similar measures for genetic distance the large number of RAPD markers available made RAPD analysis more reliable for analysis of the extremes (e.g. closely related taxa may show no isozyme differences and distant taxa may show no isozyme similarities)