Isozymes and restriction fragment length polymorphisms were used as markers in the construction of a genetic map of the citrus nuclear genome. The map was based on the segregation of 8 isozyme, 1 protein, and 37 RFLP loci in 60 progeny of a cross of two intergeneric hybrids, 'Sacaton' citrumelo (Citrus paradisi Macf. x Poncirus trifoliata (L.) Raf.) and 'Troyer' citrange (C. sinensis (L.) Osbeck x P. trifoliata), often used as rootstocks. The map contains 38 of 46 studied loci distributed on ten linkage groups. A genome size of 1,700 cM was estimated from partial linkage data. Approximately 35% of the genome should be within 10 cM and 58% within 20 cM of the mapped markers. Eight loci in three linkage groups and 1 unlinked locus deviated significantly from Mendelian segregation.

The hypothesis that plants subjected to drought stress should be less susceptible to air pollution than well‐watered plants has not been adequately tested in the field. This study was conducted to determine the influence of drought stress on foliar injury and yield responses of field‐grown cotton (Gossypium hirsutum L. cv. Acala SJ‐2) to O3. Cotton grown on Hanford coarse sandy loam (coarse‐loamy, mixed, non‐acidic, thermic Typic Xerorthents) at three levels of soil water in open‐top chambers was exposed to seasonal 12‐h (0900‐2100 h) O3 concentrations of 0.015, 0.074, 0.094 and 0.111 μL L−1 in Riverside, CA. At ambient O3 concentrations (0.074 μL L−1) severely drought‐stressed (SS) cotton averaged 25% foliar injury, while moderately stressed (SO) plants averaged 56%, and optimally watered (OW) plants averaged 68% foliar injury. Lint and seed yields were significantly reduced by O3 in OW and SO plots, while SS cotton showed no yield reductions, except at 0.111 μL L−1. Yield reductions were primarily attributable to fewer numbers of bolls. Regression equations for lint yield in relation to seasonal 12‐h O3 means and total seasonal irrigation predicted yield losses at ambient O3 concentrations relative to a background O3 level of 0.025 μL L−1 of 26.2% for OW, 19.8% for SO, and 4.7% for SS cotton. The relative similarity in responses of OW and SO cotton was attributed to adaptation to drought stress by SO plants, which maintained the sensitivity of moderately stressed cotton to O3. These results suggest that low or moderate drought stress would have relatively little effect on the response of irrigated cotton to O3.

Three Cucumis sativus L. (CS) lines adapted to USA growing conditions were used as female parents in crosses to one line each of seven Cucumis sativus var. hardwickii (R.) Alef . (CH) accessions used as male parents to determine the relative combining ability of the CH accessions for six horticultural characters . The 21 Fl progenies were grown in a randomized complete block design in two locations and evaluated for fruit number, lateral branch number, fruit length, fruit length/diameter ratio, number of female flowering nodes, and days to anthesis . General combining ability (GCA) was significant for all characters in each location . Specific combining ability (SCA) was significant for all characters except days to anthesis in one location and lateral branch number in both locations . Significant location x combining ability interactions were also evident for several characters . Results suggest that CH may be useful for improving fruit yield in commercial cucumber, but that limitations may lie in the attainment of acceptable fruit .

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