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Breeding for resistance is an important strategy to manage common bacterial blight disease caused by Xanthomonas campestris pv. phaseoli (E. Smith) Dye (Xep) in common bean (Phaseolus vulgaris L.). It is necessary to determine if prior inoculation of the first trifoliolate leaf with Xcp influences subsequent reactions in other plant organs by increasing or decreasing resistance to Xcp. It is difficult to get an accurate estimate of heritability of disease reaction in pods since environment greatly affects the heritability estimate if flowering occurs over extended time periods. Thus, the disease reaction in attached pods versus detached pods was compared. A split-split plot design with two replications (growth chambers as blocks) was used, with bean lines as the whole-plot factors, Xcp strains as subplot factors, and bacterial inoculation treatments for leaf reactions or pod treatments as split-split plot factors. The first trifoliolate leaves, later developed leaves, and attached and detached pods were inoculated. No effects of prior inoculation on the disease reactions of subsequently inoculated leaves and pods were observed, indicating that the different plant organs can be inoculated at different times. The fact that detached and attached pods showed similar disease symptoms would suggest use of the former to reduce environment variance and improve heritability estimates of resistance.
Breeding for resistance is a major method to control the common bacterial blight disease caused by Xanthomonas campestris pv phaseoli (Xcp) in common bean (Phaseolus vulgaris L.). It is necessary to determine if prior inoculation of the first trifoliolate leaf with Xcp will influence the subsequent reaction in other plant parts through induced resistance. It is difficult to get an accurate estimate of heritability (H) of disease reaction in pods since environment (E) greatly affects the H estimate if flowering occurs over extended time periods. Thus the disease reaction in attached pods vs detached pods was also observed. Four common bean lines were used in a split plot design with two replications. Two bacterial strains were used for inoculations. Two growth chambers were used as replicates. The first trifoliolate leaves, later developed leaves and attached pods and detached pods were inoculated. No effect of prior inoculation on the disease reactions of subsequently inoculated leaves and pods were observed indicating that the different plant parts can be inoculated at different times. Detached and attached pods showed similar disease symptoms. The former may be used to reduce E variance and improve H estimates.
The heritability of leaf, pod, and seed reactions; stem color and abaxial leaf pubescence; and the association of these traits were studied in advanced dry bean recombinant inbred lines derived from the Phaseolus vulgaris crosses `PC-SO' × XAN-159, `PC-50' × BAC-6, and `Venezuela 44' × BAC-6. The reaction to Xcp was quantitatively inherited in all three plant organs. Qualitative inheritance was found for stem color and leaf pubescence. Low to intermediate heritability values were obtained for the leaf and seed reactions to Xcp. Heritability estimates were consistently low for the pod reaction to Xcp. Low nonsignificant Pearson correlations were detected between leaf and pod reactions, leaf and seed reactions, and pod and seed reactions, except for the latter two correlations, which were low and significant in lines from the cross `PC-50' × XAN-154. Genetic correlations between leaf and pod reactions and leaf and seed reactions were low and significant in lines from all crosses, except for Venezuela 44 × BAC-6 in the latter case. Genetic correlations between pod and seed reactions were low and nonsignificant, except in the cross `PC-50' × XAN-159, for which a low significant correlation was observed. No significant association was found between Xcp leaf reaction and stem color or leaf pubescence. A breeding strategy for improving resistance to Xcp in P. vulgaris is discussed.
Abstract
Common blight in beans (Phaseolus vulgaris L.), incited by Xanthomonas campestris pv. phaseoli (Smith) Dye, is a serious seedborne disease in various parts of the world. We tried to detect possible differences in seed infection and transmission of bacteria in selected bean cultivars/lines. Dry seeds, flower buds (24 to 36 hr before anthesis), small pods (2 to 3 days old), and green seeds of individual plants of Bac-6, ‘Venezuela 44% ‘Pompadour Checà’ dry beans, and of dry seed of Great Northern (GN) ‘Tara’ were examined for possible internal infection after inoculating the seeds, seedlings, and plants with common blight bacterium at various sites. Inoculation of the pedicels of the flower buds and small pods resulted in transmission of the bacteria through the vascular tissue of the pod to the seeds, causing internal infection without any external symptoms shown either by the pods or seeds. Bac-6 was resistant to seed infection, and ‘Venezuela 44’ was most susceptible, followed by ‘Pompadour Checà’ and GN ‘Tara’. Planting infected seeds did not result in a systemic transmission of the bacteria in the vascular tissue of the plants to the seeds. Infected leaves were likely to be the main source for the external infection of pods, which could lead to internal and/or external seed infection. Breeding for resistance to seed infection and transmission of bacteria should aid the control of this disease. A useful technique for assessing internal infection of seeds with the bacteria was developed.
The potato leafhopper (PLH), Empoasca fabae Harris is the most important Empoasca species attacking dry beans (Phaseolus vulgaris L.) in North America. The objective of this study was to determine the heritability (h2) of PLH injury based on parent-offspring regression analysis of F3 means on individual F2 plants derived from crosses of pinto `Sierra' (resistant) × great northern `Starlight' (susceptible), and black bean `Tacarigua' (resistant) × `Starlight' (susceptible). Low narrow-sense heritability values of 0.29 ± 0.06 and 0.28 ± 0.10, respectively, were obtained for the above crosses. The low narrow-sense heritability estimates indicated large environmental effects on the expression of PLH injury in dry beans. An allelic test showed that both resistant parents possessed the same genes for resistance.
The concept that greater callus mass will induce competence was investigated. The second most immature nodal segments were removed from heavily fertigatcd greenhouse grown plants. Shoots initiated from those nodes were only cut back to one-third their total length. They were subjected to the following treatments: (1) dicamba from 1μM to 5μM in increments of 1.0; (2) B5 medium salt concentrations from 1/3x to 5/3x in increments of 1/3; (3) sucrose levels from 2% to 10% in increments of 2; (4) casein hydrolysate from 0 to 200mg/l in increments of 50. The experiment consisted of twenty-five different treatment combinations in a central composite rotatable second order design. Explants were placed in continuous cool white fluorescent light at 26°C.
Dicamba, B5 salts, and sucrose had significant effects on callus mass (p<.12), while casein hydrolysate had no notable effects on callus mass (p ≥ .57). It was determined that optimum response occurred at 5/3x concentration of B5 salts, 10% sucrose, and 5.0μM dicamba. White, compact calli were observed in treatment combinations that yielded callus fresh weights of two-hundred milligrams or higher.
Heritabilities (H) of seed transmission and leaf and pod reactions to common bacterial blight (CBB) Xanthomonas campestris pv. phaseoli (Xcp) and to web blight (WB) Thanatephorus cucumeris (Tc) were studied. The reaction to CBB was quantitatively inherited. H values of .36, .46, and .34 for leaf reaction, .14, .12, and .27 for pod reaction, .53, .26, and .36 for seed transmission were estimated based on variation of F6 lines derived from bean crosses 'PC-50' × XAN-159, 'PC-50'× BAC-6, and 'Venezuela 44' × BAC-6 (greenhouse, NE). No significant correlations were detected between leaf and pod reactions or between pod reaction and seed transmission. Quantitative inheritance patterns were observed for leaf reactions to Xcp, Tc, and architecture (AR) in F6lines from the cross BAC-6 × HT 7719 (field, Dominican Republic). H values of .23 (CBB), .14 (WB), and .30 (AR) were obtained. No significant correlations were detected between CBB with WB or AR. A low correlation (+.22) was found between WB and AR.
Four bell pepper (Capsicum annuum L.) cultivars were evaluated for yield (total weight of marketable fruit) performance over 41 environments as combinations of 3 years, three planting dates, and seven locations across North Carolina, South Carolina, and Georgia. Cultural practices, including trickle irrigation and double rows planted on black-plastic-covered beds, were uniform across all environments, except for fertilization, which was adjusted at each location based on soil tests. Comparing production over 3 years between the mountain location and the Coastal Plain location in North Carolina, yields were lower on the Coastal Plain. Spring plantings provided higher yields than summer plantings at both locations. Yield increases were obtained from hybrid cultivars over that of the open-pollinated (OP) standard [`Keystone Resistant Giant #3' (KRG#3)] in the summer planting in the mountains compared to the Tidewater Coastal Plain. Across the three-state region, hybrid cultivar yields were higher than those of the OP cultivar for the second spring planting date in 1986 and 1987. Although the hybrid yields were higher than that of the OP standard, the hybrid `Skipper' yielded less than the other hybrids (`Gator Belle' and `Hybelle'). `Gator Belle' generally out-yielded `Hybelle' at all locations, except in Fletcher, N.C. This difference may be related to the relative sensitivity of these two cultivars to temperature extremes, rather than soil or geographic factors, because there was a tendency for `Hybelle' yields to exceed `Gator Belle' in the earliest planting date. Based on the reliability index, the chance of outperforming KRG#3 (the standard) was 85% for `Hybelle', 80% for `Gator Belle', but only 67% for `Skipper'.
Nontimber forest products (food, herbal medicinals, and woody floral and handicraft products) produced in forest, agroforestry, and horticultural systems can be important sources of income to landowners. White-tailed deer (Odocoileus virginianus) can reduce the quality, quantity, and profitability of forest products by browsing twigs and rubbing stems, resulting in direct and indirect losses to production enterprises. We evaluated deer damage (frequency and intensity of browsing and rubbing) sustained by 26 species of trees and shrubs, the relationships among morphological features of trees and shrubs to damage levels, and the economic impacts of deer damage on the production of nontimber forest products. Levels of browsing were high (frequency >93% and intensity >50%) in most species of trees and shrubs, with the highest intensity (>60%) occurring in chinese chestnut (Castanea mollisima) and dogwood (Cornus spp.), and the lowest (<20%) in ginkgo (Ginkgo biloba), curly willow (Salix matsudana), ‘Scarlet Curls’ curly willow, smooth sumac (Rhus glabra), and pussy willow (Salix caprea). Species of trees or shrubs with one or a few stout stems unprotected by dense branching [e.g., american elderberry (Sambucus canadensis), smooth sumac, and curly willow] sustained the most damage by rubbing. Trees and shrubs with many small diameter stems or with dense tangled branching [e.g. redozier dogwood (Cornus sericea), forsythia (Forsythia suspensa), ‘Flame’ willow (Salix alba), and ‘Streamco’ basket willow (Salix purpurea)] were damaged the least by rubbing. Annual economic costs of deer damage to producers of nontimber forest products can range from $26/acre for pussy willow to $1595/acre for curly willow.