Inheritance of resistance to the papaya ringspot virus-watermelon strain from two different accessions of winter squash Cucurbita maxima Duch.
Inheritance of resistance to the papaya ringspot virus-watermelon strain (= PRSV-W, syn. watermelon mosaic virus-1 = WMV-1) was studied for two Cucurbita maxima accessions – ABL-010 and Redlands Trailblazer – considered to be resistant to the potyvirus. ABL-010 (ABL) derives its resistance from Brazilian accessions of C. maxima. Redlands Trailblazer (RT) is an Australian cultivar of C. maxima, the resistance of which traces back to C. ecuadorensis. In both cases, virus could be recovered from the inoculated (symptomless) plants via back inoculation onto susceptible C. pepo cultivar Caserta, indicating a tolerance type of resistance. Both ABL and RT were crossed to each other and to the standard PRSV-W-susceptible cultivar Buttercup (B). For each one of the crosses (ABL ×> B), (ABL × RT) and (RT × B), parental lines, F1, F2 and backcrosses to both the parents (BC1P1 and BC1P2) were tested for PRSV-W resistance after mechanical inoculation. Seedlings were inoculated at the first true leaf stage with a known PRSV-W isolate in 0.02 M phosphate buffer (pH 7.0) plus sodium sulphite 0.01%. Plants were scored for virus symptoms 28 days after inoculation; symptom severity being rated with a scale from 0 (= no symptoms) to 5 (= plants with severe mosaic and leaf distortions). Broad and narrow-sense heritabilities of PRSV-W resistance were 0.44/0.36, 0.59/0.59 and 0.58/0.58 for crosses (ABL × B), (ABL × RT) and (RT × B), respectively. Resistance imparted by ABL in cross with susceptible B could be explained by the action of three genes with partial dominance. Resistance imparted by RT in cross with B was found to be under control of at least two genes with additive effects. Susceptible plants were found in segregating populations of the cross ABL × RT (transgressive segregation), indicating that at least one of the loci involved in the control of resistance in ABL was not allelic to their counterpart loci in RT. The resistance imparted by RT appears to be of higher level than that imparted by ABL.
Cucurbit crops and their viral diseases in Latin America and the Caribbean islands: a review.
Cucurbit crops are cultivated throughout the world. Melon (Cucumis melo L.), cucumber (Cucumis sativus L.), watermelon (Citrullus lanatus (Thumb.) Mat. et Nak.), squash and pumpkin (Cucurbita spp) are the major crops. In Latin America and the Caribbean islands (LAC) cucurbits are consumed as a part of the daily diet since pre-Columbian times, when some species such as Cucurbita pepo L., Cucurbita moschata Duch. and Cucurbita maxima Duch. were domesticated by American Indians. In LAC, cucurbit crops have become export commodities and a source of income for several countries, in addition to their role in local consumption. The increase of area devoted to cucurbit crops and the intensification of production has led to the emergence of severe viral epidemics that threaten the sustainability of these cultures. This paper reviews the cucurbit viruses described in the region and their impact. In addition, the potential of different measures to control the most frequent cucurbit viruses in LAC is discussed.
The status of FAO and codex alimentarius developments on vegetable proteins
The FAO is interested in increasing world protein supplies both by advising and assisting developing countries to increase their production of staple foods and by encouraging the development of technology to produce protein concentrates both from vegetable and animal sources to supplement diets which are low in protein content. Recent revisions of the amount of protein required in the diet in relation to total per capita energy requirements and the difficulties encountered in introducing novel foods into established dietary patterns has led FAO to concentrate on increased agricultural productions in developing countries as the primary means of combatting malnutrition. In the meantime, in North America and Europe, advances in the technology of processing vegetable proteins has given highly acceptable products simulating meats which are being used as meat extenders and meat analogues. The consequent increase in vegetable protein production has revealed a need for international, agreement on standardization, and it has been agreed that this will be undertaken by the Joint FAO/WHO Food Standards’ Programme. The program operates chiefly through the Codex Alimentarius, Commission, an international governmental body, the purpose of which is to protect consumers against health hazard in food and against fraud. The Commission, which has 116 member governments, controls an intensive program of work covering the composition, labeling, additives, contaminants, pesticide residues, hygiene, sampling and analysis aspects of foods and has established a procedure which allows member governments ample opportunity to reach agreement on food standards and to accept them for incorporation into national legislation. The Codex Commission, at its 12th session, decided to establish a Committee on Vegetable Proteins with the following terms of references: “to elaborate definitions and world-wide standards for vegetable protein products deriving from soybeams, cottonseed, groundnuts, cereals and from other vegetable sources as they come into use for human consumption, and to elaborate guidelines on utilization of such vegetable protein products in the food supply system, on nutritional requirements and safety on labeling and on other aspects as may seem appropriate.” The question of which country will host the Committee is still under discussion.