This study aims to understand the main nutrient composition and comprehensively evaluate the differences in the mineral element contents of fruits of different macadamia cultivars, as well as screen good cultivars that are suitable for use in rocky desert mountains. Nine macadamia nut cultivars were selected as test materials in rocky desert mountain orchards. The contents of crude fat, crude protein, and total soluble sugar in kernels and N, P, K, Ca, Mg, Fe, Mn, Cu, Zn, and B in peels and kernels were determined, respectively. Then, the kernels’ mineral element contents were comprehensively evaluated based on principal component analysis. The results showed that the kernels were rich in crude fat, protein, and soluble sugar, with the crude fat content reaching 75% or greater, and the variation among cultivars was small. However, the variation in soluble sugar content was extensive. The content of mineral elements varied in different cultivars and parts of the fruit, with the average macronutrient content being K > N > Ca > P > Mg in the pericarp and N > K > P > Mg > Ca in the kernel, and the content of micronutrients in the pericarp and the kernel being Mn > Fe > Zn > Cu > B. By principal component analysis, the 10 mineral nutrient indexes were calculated as four principal components, with a cumulative contribution rate of 88.051%. Using the affiliation function value method and the calculation of the comprehensive evaluation value, the nine cultivars could be classified into three categories. The cultivar with the highest comprehensive evaluation value of the mineral element content was O.C. The one with the lowest value was H2, which indicated that O.C is a suitable variety for popularization in rocky desert mountainous areas. Stepwise regression analysis concluded that P, K, Fe, Mn, and Cu were the indicators significantly influencing the mineral element content of macadamia nuts and fruits in rocky desert mountains.

Guizhou Province is one of the regions in China where macadamia is cultivated. The area is characterized by prominent karst landforms, with uneven distribution of precipitation and utilizable water resources, which poses significant challenges to macadamia production. To explore the effects of different drought levels on the anatomical structure and physiological characteristics of macadamia seedlings, and to reveal their adaptation mechanisms and regulatory responses to drought stress, this study established a drought stress experiment on O.C (Own Choice) macadamia seedlings. The seedlings were subjected to stress in a 25% PEG-6000 solution for 0 h (CK), 24 h, 36 h, 48 h, and 72 h, and cellular structural features of stems and leaves were measured, as well as physiological and biochemical indices. The results indicated that macadamia seedlings gradually exhibited dehydration and chlorosis with prolonged drought stress. At 72 h of drought stress, root water potential, leaf water potential, chlorophyll content, relative water content, and root activity decreased by 353%, 98%, 44%, 72%, and 79%, respectively. Leaf thickness, palisade tissue thickness, and spongy tissue thickness were reduced by 19%, 33%, and 29%, respectively. Stomatal density increased by 50%, while stomatal aperture, vessel diameter, and cell wall thickness significantly decreased. Photosynthesis was markedly impaired: Pn, Tr, Gs, WUE, Fv/Fm, qP, and ΦPSII declined by 73%, 25%, 67%, 64%, 0.23, 60%, and 84%, respectively, whereas Ci and qN increased by 107% and 11%, respectively. Cell membranes began to sustain damage after 24 h of drought stress, with electrolyte leakage and MDA content rising by 266% and 672%, respectively, at 72 h. Prolonged drought stress reduced IAA, CTK, and GA levels by 37%, 33%, and 16%, respectively, while ABA content increased by 48%. To counteract drought stress, seedlings activated osmotic adjustment and reactive oxygen species (ROS) scavenging mechanisms. Osmolyte content significantly increased with stress duration, reaching 61%, 73%, 697%, and 107% increments in SS, SP, Pro, and betaine at 72 h. Antioxidant enzyme activities initially rose, peaking at 24 h (SOD, POD, CAT, and APX increased by 132%, 288%, 110%, and 46%, respectively), then gradually declined. By 72 h, SOD and APX activities fell below control levels, while POD and CAT remained elevated. These findings demonstrate that under PEG-6000-simulated drought stress, macadamia seedlings alleviate damage by modifying leaf and stem cellular structures and activating antioxidant and osmotic adjustment mechanisms. This study provides a theoretical basis for understanding the physiological mechanisms of macadamia drought stress response.

This study aimed to provide foundational research for the biological control of postharvest avocado fruits anthracnose and establish a microbial system of postharvest avocado fruits. The high-throughput sequencing of avocado fruits from the anthracnose-infected and healthy groups was performed using Illumina NovaSeq second-generation sequencing technology. The results revealed that, except for Colletotrichum sp. strain 38#, there were differences in the bacterial community structure of avocados before and after infection, as determined through alpha and beta diversity analysis. Additionally, there were significant differences in the endophytic fungal community structure, allowing clear differentiation between the infected and healthy avocados. The endophytic bacterial community was primarily composed of 4 phyla and 10 genera, with the Bacteroidota phylum and Chryseobacterium genus demonstrating sensitivity to anthracnose pathogens, as evidenced by a decrease in their relative abundance after infection. The endophytic fungal community was characterized by 3 phyla and 10 genera. After infection, the relative abundance of 2 phyla (Anthophyta and Basidiomycota) and 7 genera (Eucalyptus, Candida, Kluyveromyces, Talaromyces, Oidiodendron, Nigrospora, and Pestalotiopsis) decreased, whereas the relative abundance of the Colletotrichum genus increased dramatically. The LEfSe (Linear discriminant analysis Effect Size) analysis indicated that significant biomarkers were more prevalent in endophytic bacteria than in endophytic fungi in the avocados. In endophytic bacteria, the key biomarkers included the Firmicutes phylum (Bacilli class), Proteobacteria phylum (Gammaproteobacteria class, Pseudomonadales order, Pseudomonadaceae family, and Pseudomonas genus), Flavobacteriales order, Weeksellaceae family, and Chryseobacterium genus. In endophytic fungi, the important biomarkers were Saccharomycetes class (Saccharomycetales order), Glomerellales order (Glomerellaceae family and Colletotrichum genus), and Botryosphaeriales order (Botryosphaeriaceae family and Lasiodiplodia genus). These results may provide a theoretical basis for the development of future biological agents for avocado anthracnose.