Carlos Agustin Rava

Genetic control of Fusarium wilt in common bean

O objetivo do trabalho foi determinar o controle genetico da resistencia do feijoeiro comum ao patotipo FOP 46 de Fusarium oxysporum f. sp. phaseoli e estimar parâmetros geneticos da resistencia a doenca. Em casa de vegetacao, as avaliacoes da resistencia foram conduzidas em familias F2:3 dos cruzamentos Milionario 1732 x Macanudo e FT-Taruma x Macanudo. Os sintomas da doenca foram avaliadas nas plantas aos doze dias apos a inoculacao, atribuindo-se notas que variavam de 1 (plantas sem sintomas) a 9 (plantas totalmente murchas e ou mortas). A analise das frequencias observadas de plantas resistentes e suscetiveis na populacao F2:3 resultantes da autofecundacao das plantas F2 dos cruzamentos Milionario 1732 x Macanudo e FT Taruma x Macanudo, sugeriu um gene efeito maior com acao genica de dominância incompleta. O aparecimento na familia F2:3 de genotipos transgressivos sugere a natureza oligogenica da resistencia da murcha do fusario. As estimativas de herdabilidade e predicao de ganho por selecao foram elevadas em ambos os cruzamentos.

Reaction of common bean cultivars to angular leaf spot in the greenhouse

Twenty-three common bean (Phaseolus vulgaris) genotypes were tested for reaction to angular leaf spot disease caused by Phaeoisariopsis griseola in the greenhouse. All genotypes were tested with monosporic isolates Ig 664 and Ig 669, characterized as pathotypes 63.23 and 63.19, respectively. Fourteen-day-old plants (vegetative stage V3) were inoculated with a suspension containing 2.5 × 104 conidia/mL. This suspension was applied to the upper and lower leaf surfaces. Disease symptoms were evaluated 14 and 18 days after inoculation by using a rating scale varying from 1 (no symptoms) to 9 (> 25% of leaf area with angular leaf spot lesions). Culivars BRS Valente, CNFC 10281, CNFP 10138, BRS Grafite, BRS Requinte, BRS Pontal, MAR 02, Cornell 49-242 and AND 277 showed resistance to both isolates. Cultivars Carioca Rubi, CNFC 9504, CNFC 10150 and Soberano were susceptible to both pathotypes. Pathotype 63.23 was the most virulent. The new resistance sources identified in this work could be used in common bean breeding programs aiming to incorporate resistance to angular leaf spot in new common bean cultivars.

Linhagens de feijoeiro comum com fenótipos agronômicos favoráveis e resistência ao crestamento bacteriano comum e antracnose

Common bacterial blight and anthracnose diseases, incited by Xanthomonas axonopodis pv. phaseoli (Smith) Vauterin, Hoste, Kesters & Swings and Colletotrichum lindemuthianum (Sacc. & Magn.) Scrib., respectively, are major constrains for dry bean (Phaseolus vulgaris L.) production. The main objective of this work was to obtain lines resistant to common bacterial blight, anthracnose and desirable agronomic characteristics. Thirty five F2 populations from single crosses between lines having resistance to common bacterial blight originated from P. acutifolius A. Gray, with bush plant type lines having lodging and anthracnose resistance, were obtained. Segregating populations from F2 to F5 inoculated in the field with spore suspension of pathotype 89 of C. lindemuthianum at a concentration of 1.2 x 106 conidia/ml, were submitted to negative mass selection. Plants showing score higher than 4 were eliminated. In F5, at harvest time, individual selection was performed to alelorate F6 families. The F6 families were evaluated by inoculation with pathotypes 55, 89, 95 and 453 of C. lindemuthianum. The F7 anthracnose resistant families were inoculated in the greenhouse by clipping the primary leaves with scissors dipped in a bacterial suspension of 5 x 107 cfu/ml of XpCNF 15 isolate of X. axonopodis pv. phaseoli. Resistant lines were evaluated in four yield trials. Seventeen high yielding non lodging lines, resistant to common bacterial blight and anthracnose with upright plant type were selected.