Domesticated chile (Capsicum annuum L. var. annuum) is a widely cultivated spice and vegetable crop. It originated in the Western Hemisphere, but spread rapidly throughout the globe after the voyage of Columbus. However, very little is known about the genetic diversity of chile in Asia and especially in Nepal. Thus, research was conducted to document morphological as well as molecular characterization of C. annuum var. annuum landraces collected from Nepal. Genetic diversity in C. annuum var. annuum landraces from Nepal was investigated using randomly amplified polymorphic DNA (RAPD) markers and compared with that of C. annuum var. annuum landraces from the center of diversity, Mexico. RAPD marker based cluster analysis of C. annuum var. annuum clearly separated each accession. All accessions of C. annuum var. annuum from Nepal grouped into a single cluster at a similarity index value of 0.80, whereas, accessions from Mexico grouped into eight different clusters at the same similarity level indicating greater genetic diversity in Mexican accessions. RAPD analysis indicated that the Nepalese chile population went through an additional evolutionary bottleneck or founder effect probably due to intercontinental migrations. Some Nepalese accessions had unique RAPD markers suggesting that additional sources of genetic variation are available in Nepalese germplasm.
The effect of temperature on CO2 fixation was studied in 2 tomato (Lycopersicon esculentum Mill.) cultivars; the heat-sensitive “Roma VF” and the heat-tolerant “Saladette". A decrease in apparent photosynthesis was found in both cultivars after plant exposure for various lengths of time to temperatures of 35° to 40°C. An increase in temperature also increased transpiration and raised the CO2 compensation point. The decrease in photosynthesis after a short exposure to high temperature was due to an increase in mesophyll resistance and, to a lesser extent, to an increase in stomatal resistance to CO2 diffusion. Saladette was less affected by high temperature and had a slightly greater photosynthetic capacity than the heat-sensitive Roma VF, after pretreatment at high temperature.
Mature Marsh seedless grapefruit trees on Sour orange stock planted in a loamy soil were subjected to three levels of nitrogen fertilization with and without phosphate or chicken manure added. The details of the experimental plan and tree responses during the five-year experimental period will be described elsewhere. Briefly, the phosphate and manure treatments resulted in a significant increase in yield and in improved fruit quality. As far as the leaf composition is concerned, the phosphate and manure treatments caused an increase in the P and a decrease in the N content of the leaves, thus producing a completely inverse relationship between leaf N concentration and the yield of the corresponding trees. This situation served as an opportunity to test—under orchard. conditions—the validity of NaR (nitrate reductase) assay in leaves as a measure for some “active fraction” of leaf nitrogen and as a parameter for tree productivity. The use of the NaR assay has been suggested for the determination of N requirements of citrus trees (1).
On a whole-plant basis, deblossomed ‘Tribute’ strawberry plants had higher rates of net photosynthesis (Pn) and greater leaf area than fruiting plants during the last 3 weeks of a 6-week fruiting cycle. Leaves of both fruiting and deblossomed plants had a greater dry weight and total nonstructural carbohydrate (TNSC) content than the roots, crown, or fruit. At the end of the fruiting cycle, dry weight and TNSC content of leaves were higher for deblossomed plants than fruiting plants. There was no difference in crown or root dry weights between treatments. Pn was highly correlated with plant dry weight and TNSC during the 3rd, 5th, and 6th weeks of the fruiting cycle.
Peroxidase activity measured on leaf disks of vegetable plants is suggested as a rapid tissue test for diagnosing iron deficiency. The reaction is rapid, may be executed under field conditions and apparently corresponds with the metabolically active part of the iron in the leaf tissue.
Blossom-end rot (BER) is one of the major physiological disorders of green-house bell pepper (Capsicum annuum L.). The objective of the present work was to study the effects of the solution N concentration and N-NO3: N-NH4 ratio on fruit yield and the incidence of BER and other fruit-quality traits of greenhouse-grown bell pepper in a Mediterranean climate. Three experiments were conducted: Expt. 1 included five total N concentrations (0.25 to 14 mmol·L-1, with a constant N-NO3: N-NH4 ratio of 4); Expt. 2 included five treatments of different NO3: NH4 molar ratios (0.25 to 4, with a constant N concentration of 7 mmol·L-1); and Expt. 3 included three treatments of different NO3: NH4 molar ratios (1.0, 3.0 and 9.0, with a constant N concentration of 7 mmol·L-1). Plants were grown in an aero-hydroponics system in Expts. 1 and 2 and in tuff medium in Expt. 3, in greenhouses in Israel. The optimal values of N concentration for total fruit yield and for high fruit quality (marketable) were 9.3 and 8.3 mmol·L-1, respectively. The total and high-quality fruit yields both increased with increasing N-NO3: N-NH4 ratio in the range studied. The total and high-quality fruit yields both decreased sharply as the NH4 concentration in the solution increased above 2 mmol·L-1. The increase in the NH4 concentration in the solution is the main cause of the suppression of Ca concentration in the leaves and fruits and the increased incidence of BER. The occurrence of flat fruits also increased with increasing NH4 concentration in the solution.