4 research outputs found
Transcriptomics reveal the genetic coordination of early defense to Armillaria root rot (ARR) in Prunus spp
Armillaria root rot (ARR) poses a significant threat to the long-term productivity of stone-fruit and nut crops in the predominant production area of the United States. To mitigate this issue, the development of ARR-resistant and horticulturally-acceptable rootstocks is a crucial step towards the maintenance of production sustainability. To date, genetic resistance to ARR has been found in exotic plum germplasm and a peach/plum hybrid rootstock, ’MP-29‘. However, the widely-used peach rootstock Guardian® is susceptible to the pathogen. To understand the molecular defense mechanisms involved in ARR resistance in Prunus rootstocks, transcriptomic analyses of one susceptible and two resistant Prunus spp. were performed using two causal agents of ARR, including Armillaria mellea and Desarmillaria tabescens. The results of in vitro co-culture experiments revealed that the two resistant genotypes showed different temporal response dynamics and fungus-specific responses, as seen in the genetic response. Gene expression analysis over time indicated an enrichment of defense-related ontologies, including glucosyltransferase activity, monooxygenase activity, glutathione transferase activity, and peroxidase activity. Differential gene expression and co-expression network analysis highlighted key hub genes involved in the sensing and enzymatic degradation of chitin, GSTs, oxidoreductases, transcription factors, and biochemical pathways likely involved in Armillaria resistance. These data provide valuable resources for the improvement of ARR resistance in Prunus rootstocks through breeding
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Effects of Cytokinin on Multiplication and Rooting of Aloe barbadensis during Micropropagation on Agar and Liquid Medium
Aloe barbadensis (syn. Aloe vera) was micropropagated on agar and liquid medium at varied benzyladenine (BA) and meta-topolin (MT) concentrations (0, 1, 3.2, and 10 µM) for three successive culture cycles and then transferred to a greenhouse for growth. MT induced multiplication at the highest concentration (10 µM) and BA produced the greatest number of plantlets (at 3.2 µM) with optimal multiplication at approximately 6 µM. Liquid medium did not affect multiplication rate when compared with agar, but plants were twice as large from liquid as compared with those from agar at the time of transfer to the greenhouse. After five weeks of growth, plants in the greenhouse micropropagated on liquid culture were still larger than plants micropropagated on agar with BA and MT. A carryover of cytokinin inhibited rooting, and plants on agar were more severely affected than plants on the liquid medium. Cytokinin carryover reduced rooting from 92% (control) to 68% with either the 3.2 µM MT or 10 µM BA and at 10 µM MT only about 20% of the aloe plants rooted. There appeared to be a trade-off between maximum multiplication rates and best plant quality for ex vitro transfer. Using liquid medium led to larger plants and lessened the cytokinin carryover effect on rooting without affecting the multiplication rate. Approximately 6 µM BA in liquid medium would be optimal for multiplication and rooting of A. barbadensis