Location: Tropical Crops and Germplasm Research2013 Annual Report
1a. Objectives (from AD-416):
Evaluate tropical/sub-tropical fruit production systems and germplasm for broad agro-environmental adaptation, high yield and productivity, and ability to produce fruits of superior quality. Develop efficient and sustainable monitoring and/or control methods for key pests that limit tropical/subtropical fruit production and quality.
1b. Approach (from AD-416):
Field evaluations for yield and fruit quality traits of selected tropical fruit crop scion and/or rootstock germplasm will be conducted in various agro-environments. Nutrient requirements and utilization efficiency studies will be conducted to optimize nutrient applications. Control strategies for plant pathogens of tropical and subtropical fruit crops will be developed using systemic acquired resistance agents. Strategies to increase pollinators in Annonaceae will be developed. Field evaluation of biological agents for biocontrol of important insect pests of tropical and subtropical fruit crops will be conducted.
3. Progress Report:
The following research was conducted: 1) an experiment to evaluate six lychee cultivars for yield and fruit quality traits at two locations in Puerto Rico was completed and data is being analyzed for publication of results; 2) an experiment to evaluate 12 dragon fruit (pitahaya) cultivars and lines continued for an additional year to determine if yield of cultivars level off and to determine if fruit is host to Anastrepha spp. fruit flies; 3) An experiment (year 2) to screen mamey sapote germplasm for acid soil tolerance was harvested and biomass production for each accession determined. Data is being analyzed for publication of results; 4) a greenhouse experiment to determine the effect of soil pH and various concentrations of iron on early growth of mangosteen trees was completed and data is being analyzed for publication of results; 5) an experiment to evaluate three longan cultivars as rootstocks and in combination with three scions continued and should be completed late in FY13; 6) an experiment to evaluate 16 sapodilla cultivars as rootstocks was completed and data is being analyzed for publication of results; 7) an experiment to study the performance of 12 cacao accessions propagated by grafting and somatic embryogenesis was completed and data is being analyzed for publication of results; 8) the third year of an experiment to evaluate cultivar FHIA-17, a Sigatoka-tolerant banana, for yield and fruit quality traits was completed; 9) an experiment to evaluate cultivar FHIA-21, a Sigatoka-tolerant plantain, for yield and fruit quality traits at two locations will be completed at the end of the fiscal year; 10) an experiment to determine nutrient uptake of four mamey sapote and four rambutan cultivars grown at two locations in Puerto Rico will continue for one more year; 11) Identification of the aphid species that make up seasonal peaks and potentially contribute greatest to the spread of papaya ringspot virus is in progress. Aphis spiraecola, makes up more than 80% of these captures in Mayaguez and Isabela. We plan to expand this survey to include other parts of the island. The results from these experiments help to fill the knowledge gaps on cropping management systems for tropical/subtropical fruit crops.
1. Attracting pollinators of atemoya. Atemoya and other fruit crops in the Annonaceae family often have low yield due to poor visitation by pollinating beetles in the family Nitidulidae. Pollination is done by hand in parts of the world, but labor costs are prohibitive in the U.S. ARS researchers in Mayaguez, Puerto Rico demonstrated that commercially available lures for nitidulids attract a variety of species in a dose dependent manner and that the addition of food attractants (bread dough, apple juice and malt beverage) attracts different species of beetles. We have now begun field trials to demonstrate that this increased number of beetles translates to increased fruit set and fruit size. The lures are substantially cheaper than hand-pollination of multiple flowers per tree. The use of lures will increase the value and market of atemoya.
2. Identification of fungi attacking longan fruit. Fungi are a very large and diverse group of organisms that cause serious diseases of crop and forest plants. Accurate knowledge of fungi is critical for controlling the diseases they cause. Longan is a tropical plant that produces delicious edible fruits. ARS researchers in Mayaguez, Puerto Rico and collaborators discovered for the first time a fungus that causes fruit rot and inflorescence blight in longan trees in Puerto Rico. Knowledge of the identity of this plant pathogen is the first step to assess its impact on production of trees and to develop control measures, if necessary.
3. Susceptibility of longan to acid soils. The most productive soils of the world are already under cultivation, and those available for agricultural expansion are often strongly acid, possessing toxic levels of soil aluminum and/or manganese. These elements could drastically reduce crop yields when present in the soil at high concentrations. Incorporation of lime to the soil is a common practice to ameliorate acidity but it is not very effective below the plough layer and often lime is not available to farmers with limited resources. The effect of soil acidity factors on dry matter production and leaf nutrient composition of four longan cultivars was assessed by ARS scientists in Mayaguez, Puerto Rico during a 2-year field study. High concentrations of soil aluminum (Al) resulted in a 75% reduction in total dry matter production which is indicative that this crop is highly susceptible to acid soils rich in soil Al. Future efforts should be devoted to the screening of longan germplasm to identify Al-tolerant genotypes which could be used as rootstocks in acid soils.Jenkins, D.A., Kendra, P.E., Van Bloem, S., Whitmire, S., Mizell, R., Goenaga, R.J. 2013. Forest fragments as barriers to fruit fly dispersal: Anastrepha (Diptera: Tephritidae) populations in orchards and adjacent forest fragments in Puerto Rico. Environmental Entomology. 42(2):283-292.