Genetic resistance to plant viruses has been used for at least 80 years to control agricultural losses to viral diseases. To date, hundreds of naturally occurring genes for resistance to plant viruses have been reported from studies of both monocot and dicot crops, their wild relatives, and the plant model, Arabidopsis. The isolation and characterization of a few of these genes in the past decade have resulted in detailed knowledge of some of the molecules that are critical in determining the outcome of plant viral infection. In this chapter, we have catalogued genes for resistance to plant viruses and have summarized current knowledge regarding their identity and inheritance. Insofar as information is available, the genetic context, genomic organization, mechanisms of resistance and agricultural deployment of plant virus resistance genes are also discussed.

Genetics of Plant Virus Resistance

Advances in cowpea research , Advances in cowpea research , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Advances in cowpea research

Knowledge, access, and use of diversity available in cultivated and wild relatives are essential for broadening the genetic base of cultivars to sustain improvement. My objectives are to review briefly the origin, domestication, and organization of genetic diversity in Phaseolus beans, highlight production problems and traits deficient in the common bean (P. vulgaris L.) cultivars, cite sources of useful gemplasm, and review progress achieved in broadening the genetic base of cultivars. Phaseolus beans originated in the Americas. Only five species, P. acutifolius A. Gray, P. coccineus L., P. lunatus L., P. polyanthus Greenman, and P. vulgaris L. were domesticated. The interspecies diversity in relation to common bean is organized in primary, secondary, tertiary, and quaternary gene pools. Intraspecies diversity in common bean is separated into two major gene pools (Andean and Middle American). Cultivars are further divided into races, each with their distinguishing characteristics. Also, cultivars of dry seed and snap bean exist. Abiotic and biotic stresses limit common bean production. The genetic base of cultivars within market classes is narrow and inadequate level of resistance to common bacterial blight [caused by Xanthomonas campestris pv. phaseoli (Smith) Dye] and white mold [caused by Sclerotinia sclerotiorum (Lib) de Bary] exist in cultivars. High levels of resistance to these and other desirable traits exist in the relatives and gene pools of P. vulgaris. Early maturity, adaptation to higher latitude, upright plant type, high pod quality and seed yield, and resistance to Bean common mosaic virus (a potyvirus) andlor rust [caused by Uromyces appendiculatus (Pers.:Pers.) Unger] have been bred into cultivars. However, most of the genetic variability available in the common bean races, gene pools, and wild relatives remains to be utilized. To maximize and sustain bean production, high yielding, high quality cultivars that are less dependent on water, fertilizer, pesticides, and manual labor should be developed. This need warrants sustained, comprehensive, and integrated genetic improvement, in which favorable alleles from cultivated and wild relatives are accumulated in superior cultivars. A three-tiered breeding approach involving:(i) gene introgression from alien germplasm, (ii) pyramiding favorable alleles from different sources, and (iii) simultaneous improvement of multiple traits for common bean cultivars would be the most appropriate strategies to meet theses needs.

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Broadening the Genetic Base of Common Bean Cultivars

Segregating allozyme and DNA polymorphisms were used to construct a preliminary linkage map for faba bean. Two F2 populations were analyzed, the most informative of which was segregating for 66 markers. Eleven independently assorting linkage groups were identified in this population. One of the groups contained the 45s ribosomal array and could be assigned to the large metacentric chromosome I on which the nucleolar organizer region is located. This linkage group also contained two isozyme loci, Est and Tpi-p, suggesting that it may share some homology with chromosome 4 of garden pea on which three similar markers are syntenic. Additional aspects of the map and the extent of coverage of the total nuclear genome are discussed.

Linkage among isozyme, RFLP and RAPD markers in Vicia faba

The separation ofSclerotinia sclerotiorum (Lib.) de Bary, 5.trifoliorum Erikss., andS. minor Jagger into three distinct species has been based on traditional morphological and physiological criteria such as gross cultural characteristics, sclerotial size, ascus and ascospore dimensions, time of apothecial development in the field, and host association. However, these characteristics tend to be variable and some workers have concluded that the three fungi should be included in one species, 5.sclerotiorum. Recently, new data have been published on morphological, cultural, physiological, ontogenetic, enzyme pattern, mycelial interaction, and cytological characteristics of isolates ofSclerotinia spp. This information supplements, but does not replace, that available from more traditional taxonomic methods and helps to resolve the controversy on the taxonomy and nomenclature of these fungi.

The biology of Sclerotinia sclerotiorum, S. trifoliorum, and S. minor with emphasis on specific nomenclature.

S EPIDEMICS of white mold of snap bean {Phaseolus vulgaris L.), caused by Whetzelinia (=Sclerotinia) sclerotiorum (Lib) Korf and Dumont, have occurred repeatedly in central and western New York State in recent years. The disease has caused significant economic losses, especially during prolonged periods of wet weather-. White mold epidemics in New York are initiated by ascospores produced mainly outside bean fields by sclerotia of the fungus'. Ascospores do not directly infect bean tissues in the prebloom stage, since blossoms are needed as an energy source for germination and infection '•'-. A prolonged period of wet soil is required for the production of ascospores, and 48-72 hours of continuous moisture is required for initiation of infection''. The fungus completely colonizes mature and senescent blossoms in 2-3 days. These infected blossoms then serve as an efficient source of inoculum when in contact with leaf, stem, and pod tissues. Chemical control of this disease with benomyl has been successful ', but its relatively high cost, the rigidity of the spray program, and the threat of the development of a benomyl-resistant strain of the pathogen have stimulated the search for sources of resistance in P. vulgaris and other Phaseolus species. A large number of cultivars, breeding lines, and plant introductions were evaluated using an inoculation technique and conditions that simulated natural infection (Abawi et al.; Abawi et al., unpublished data). All the accessions of P. vulgaris were susceptible, although a few plants of some lines appeared to be tolerant. However, a high degree of resistance was found in selections of P. coccineus, including a white-flowered line, B-3749, a selection of P.I. 175829. This line and other accessions of P. coccineus had been found resistant to white mold by Adams et al. using a different inoculation procedure. Recently, Coyne et al. reported that Black Turtle Soup was the most resistant dry bean germplasm to the white mold fungus under natural inoculation conditions in western Nebraska. This paper reports the inheritance of resistance in line B-3749 to W. sclerotiorum and the progress made in transferring the resistance to two commercial snap bean cultivars.

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Inheritance of resistance to white mold disease in Phaseolus coccineus

Comparative studies on host range and serology of papaya ringspot virus and watermelon mosaic virus 1

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Inheritance of Resistance to a Lentil Strain of Pea Seed-Borne Mosaic Virus in Pisum sativum

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Inheritance of Resistance to cucumber Mosaic Virus in a Transgenic Tomato Line Expressing the Coat Protein Gene of the White Leaf Strain

/pdf/inheritance-of-resistance-to-a-third-pathotype-of-pea-seed-2s10iab9sp.pdf

R. Provvidenti

Papers

Inheritance of resistance to white mold disease in Phaseolus coccineus

Comparative studies on host range and serology of papaya ringspot virus and watermelon mosaic virus 1

Inheritance of Resistance to a Lentil Strain of Pea Seed-Borne Mosaic Virus in Pisum sativum

Inheritance of Resistance to cucumber Mosaic Virus in a Transgenic Tomato Line Expressing the Coat Protein Gene of the White Leaf Strain

Inheritance of Resistance to a Third Pathotype of Pea Seed-Borne Mosaic Virus in Pisum sativum