Estimates of genetic variability for in vitro culture traits among the genus Lycopersicon and evaluation of the gene effects involved in callus production and shoot formation were achieved. Five parents including wild and cultivated tomato genotypes and their nonreciprocal 10 possible hybrid combinations were assayed. The callus percentage (C = number of cultures that only produced callus× 100/total number of cultures), the regeneration percentage (R = number of cultures that differentiated into shoots or primordia × 100/total number of cultures) and the productivity rate (PR = total number of shoots/total number of cultures) of each genotype were calculated 45 days after culture initiation. Diallel analysis revealed genetic variability for in vitro culture response. Wild genotypes contributed to a reduction in callus production and an increase in shoot formation while the cultivated genotypes either had an opposite effect or did not modify the expression of culture traits. Hybrids had the lowest callus production and highest shoot formation percentage. Additive gene effects were mainly involved in the expression of C and R, while both additive and nonadditive gene effects were involved in expression of PR.
Guillermo Pratta, Lilians N. Cánepa, Roxana Zorzoli, and Liliana A. Picardi
Gustavo R. Rodríguez, Guillermo R. Pratta, Roxana Zorzoli, and Liliana A. Picardi
A cross was performed between Lycopersicon esculentum Mill. `Caimanta' and L. pimpinellifolium (Jusl.) Mill. accession LA722. Divergent-antagonistic selection for fruit weight and shelf life started in the F2 generation. Fruit shelf life showed transgressive segregation in this F2 generation. The selection process continued until the F6 generation, but we found that only fruit weight was responsive to selection. Seventeen recombinant lines (RILs) were analyzed for both traits. Nine of these RILs were obtained by the selection process. The other eight RILs were obtained by selfing without selection from the same F2 generation to assess random drift. Highly significant differences were found among these RILs for both fruit weight and shelf life. Random drift was as important as selection in producing different genotypes. Although fruit shelf life showed null response to selection in this interspecific cross, selfing and selecting has generated a new population of 17 recombinant genotypes for both fruit weight and shelf life. This experiment has demonstrated that wild tomato species offer breeders another possibility to enhance the genetic variability for fruit shelf life and fruit weight in tomato germplasm.
Jon Y. Suzuki, Tracie K. Matsumoto, Lisa M. Keith, and Roxana Y. Myers
Nuclear and chloroplast genetic markers have been extensively used for plant identification and molecular taxonomy studies. The efficacy of genetic markers to be used as DNA barcodes is under constant evaluation and improvement with identification of new barcodes that provide greater resolution and efficiency of amplification for specific species groups as well as distantly related plants. In this study, chloroplast DNA genetic markers for Anthurium, the largest genus in the Araceae family, were adapted from chloroplast markers previously designed for Lemna minor, a member of the same plant family. Primers for chloroplast region trnH-psbA, previously used for molecular systematic studies in Anthurium, as well as primers for the rpoB, rpoC1, psbK-psbI, matK, rbcL, and atpF-atpH regions, all located within the large single copy sequence in the chloroplast genome, were evaluated and found to efficiently amplify target sequences when using DNA of varied quality and concentration extracted from silica-dried leaves of selected accessioned species of Anthurium. The trnH-psbA, psbK-psbI, and atpF-atpH intergenic region primers were further evaluated using Anthurium species spanning different subgeneric groups. Of the intergenic region primers tested, psbK-psbI primers were the most robust, yielding well-defined amplicons across Anthurium species that were consistent, with exceptions, within sectional groupings. Application of the psbK-psbI region amplicon as a visual marker for surveying sectional relationships in Anthurium is novel and serves as a model for the development of a diagnostic method for genotyping plants and testing for sample integrity from among species or germplasm collections. This work further demonstrates the use of dried plant tissue banks as a genetic reference and information resource to support basic research as well as ornamental plant characterization and improvement.
Roxana Myers, Andrea Kawabata, Alyssa Cho, and Stuart T. Nakamoto
Kona coffee root-knot nematodes (Meloidogyne konaensis) cause severe declines in ‘Kona Typica’ arabica coffee (Coffea arabica) trees in Hawaii. Defoliation and destruction of the root system result in significant yield losses and can kill the host. Grafting with other coffee (Coffea) species that exhibit tolerance to kona coffee root-knot nematodes is a viable solution for mitigating damage in the field. An infested field was established in 2006 with ‘Kona Typica’ scions grafted on seven accessions of promising rootstock and nongrafted ‘Kona Typica’ as the control. Four grafted trees of each accession were planted per plot with four repetitions. Yield data were assessed for the 2016–17, 2017–18, and 2018–19 seasons. Three liberica coffee (Coffea liberica) accessions [‘Arnoldiana’ (‘Arnoldiana’ 1 and ‘Arnoldiana’ 2), ‘Dewevrei’, and ‘Fukunaga’ 1], demonstrated higher yields of coffee cherry compared with nongrafted ‘Kona Typica’ in the 2016–17 season. In the 2017–18 and 2018–19 seasons, five accessions of liberica and ‘Nemaya’ robusta coffee (Coffea canephora) exhibited higher cherry yields than ‘Kona Typica’. Plant vigor was greater in trees grafted on ‘Arnoldiana’ and ‘Fukunaga’ compared with other accessions and nongrafted ‘Kona Typica’, with taller trees, higher vertical branches, thicker trunk circumferences, and overall better health. After 13 years in the field, nongrafted ‘Kona Typica’ showed the highest mortality, with 81% of trees lost. Liberica rootstocks performed consistently well in the presence of kona coffee root-knot nematodes, with the healthiest trees, highest yields, and least mortality of the coffee species evaluated.
Roxana Myers, Brian Bushe, Cathy Mello, Joanne Lichty, Arnold Hara, Koon-Hui Wang, and Brent Sipes
Burrowing nematode (Radopholus similis) causes severe stunting and yield reduction in anthurium (Anthurium andraeanum) cut flower production. Two field trials were conducted at commercial grower farms to test the efficacy of fluopyram or fluopyram + trifloxystrobin for managing burrowing nematodes. Nematode population densities in roots and cinder media were evaluated during the trial in addition to cut flower yield and canopy cover. In the first trial, the nematode population in roots was reduced by 57% after two applications of fluopyram 3 months apart. As plant health improved, the increasing anthurium root weight supported higher nematode populations. After 14 months, fluopyram-treated plots had 43% more green canopy cover and a 53% increase in flower production compared with the untreated control plots. At a second location, population densities of burrowing nematode were reduced in roots after one application of fluopyram + trifloxystrobin and remained low with quarterly applications. Nematode populations were initially reduced in fluopyram-treated plots followed by a resurgence as demonstrated in the other trial. Ten months after the initial treatment, flower yield was greater in fluopyram + trifloxystrobin-treated plots with more large and extra-large flowers produced. Canopy cover was 45% and 22% greater with fluopyram + trifloxystrobin and fluopyram applications, respectively. Fluopyram shows potential for management of burrowing nematodes in anthurium by improving plant vigor and cut flower production.
Edina Pászti Mendelné and Ákos Mendel
great skin color. The fruits of ‘Roxana’ have a very similar appearance (but these are a bit elongated), and the tree is less vigorous. It is another control cultivar used in the eastern part of Europe and in the Balkans ( Milošević et al., 2013