Alves, A.A.C.

Bellotti, Anthony C.

Dita, M.A.

Fregene, Martin A.

Silva, A.F.

CGSpace

 Dita, Miguel1; Alves, Alfredo1; Silva, Alineaurea2; Bellotti, Anthony3; Fregene,  Martin31Embrapa Cassava & Tropical Fruits, Cruz das Almas, Bahia, Brazil; 2Embrapa Semi-Arid, Petrolina, Pernambuco, Brazil;3International Center for Tropical Agriculture, Cali, Colombia. e-mail: miguel@cnpmf.embrapa.brEvaluation of cassava interespecific hybrids for disease resistanceIntroductionThe best method to control plant disease is the use of resistant varieties. In cassavathis is particularly important since most of producers are smallholder with lowresources/information to acquire chemical products. In Brazil, no chemical products(insecticide/fungicide) are legally authorized to be used in cassava. Thus, methodsto control cassava diseases are necessarily related to cultural practices and, mainly,to the use of resistant varieties. However, plant pathogens are highly variable andconstantly new strains/races cause breakdown of resistance. Therefore, searchingfor new sources of resistance, such as those present in cassava wild relatives isnecessary. This work aimed evaluate cassava interspecific hybrids obtained atCIAT from different M. esculenta varieties and the wild species M. flabellifollia,M. tristis and M. peruviana for disease resistance in different production areasof Brazil.Seedlings of several families planted in São Miguel das Matas (SMM), TancredoNeves (TN), Cruz das Almas (CA) in the Bahia State, and in Petrolina (PT),Pernambuco State were evaluated for disease resistance from 6 to 12 months afterplanting (MAP). Severity was assessed using scales from 0 - 5 class (0: nosymptoms and 5: maximum level of  susceptibility).ResultsIn the Bahia State (TN, SMM and CA ) the incidence of anthracnose, brown leafspot (BLS), rust, diffuse leaf spot and white leaf spot were observed. In Petrolinaonly sporadic lesions of BLS were found (Fig. 1)Anthracnose, brown leaf spot and rust, in this order, were the most severedisease in Bahia. (Tables 1, 2 and 3). Genotypes with 100% of apical shootsaffected by anthracnose, die-back, and high level of defoliation were observed.Similarly, in genotypes highly susceptible to BLS complete defoliation was observed.Respect rust, although some genotypes reached the highest class of the scale,disease intensity was lower, when compared to anthracnose and BLS, respectively.Differences in the resistance levels among progenies and among  genotypes of thesame family were observed. Regardless of the evaluation sites, in Bahia, highvariation in the resistance levels inter- and intra-families was observed. Most ofgenotypes with high levels of resistance to anthracnose and BLS were found infamilies involving M. tristis (Table 1).  For rust, however, most of the resistanthybrids had M. flabellifollia as parent.Only 8 genotypes from crosses involving M. peruviana were evaluated (4 in SMMand 4 in TN). All of them were susceptible to anthracnose and only resistance torust was recorded.Table 1. Disease resistance reaction of cassava interespecific hybrids evaluated at 12 MAP indifferent regions of BrazilTancredo NevesCruz das AlmasaValues corresponds to the number of genotypes classified as R: Resistant (classes: 0-2); IR: Intermediary resistance(class 3) and S: Susceptible (classes 4 and 5). *Values between brackets corresponds to the number of genotypes evaluatedon each progenyR RI S R RI S R RI SCW 450 (20) 0 5 15 1 1 18 12 7 1 M. flabellifoliaCW 452 (8) 0 0 8 0 1 7 3 1 4 M. flabellifoliaCW 453 (15) 1 7 7 0 0 15 11 4 0 M. flabellifoliaCW 464 (6) 1 4 1 0 0 6 2 4 0 M. flabellifoliaCW 473 (4) 0 4 0 0 0 4 2 2 0 M. peruvianaCW 444 (10) 0 7 3 2 3 5 6 2 2 M. tristis CW 445 (13) 0 13 2 4 5 5 11 2 0 M. tristis CW 482 (4) 0 3 1 0 0 4 1 3 0 M. tristis CW 485 (5) 2 3 0 1 1 3 5 0 0 M. tristis CW 488 (4) 0 1 3 0 0 4 0 3 1 M. tristis Total 4 47 40 8 11 71 53 28 8Wild speciesinvolvedFamily (*) Brown leaf spot Anthracnose RustR RI S R RI S R RI SCW 450 (20) 0 0 20 0 0 20 17 3 0 M. flabellifoliaCW 452 (8) 0 0 8 0 0 8 3 4 1 M. flabellifoliaCW 453 (15) 4 1 10 0 1 14 6 9 0 M. flabellifoliaCW 464 (5) 0 1 4 0 0 5 4 0 1 M. flabellifoliaCW 473 (4) 0 0 4 0 0 4 3 0 1 M. peruvianaCW 444 (10) 1 1 8 1 1 8 9 1 0 M. tristis CW 445 (15) 3 2 10 3 2 10 14 1 0 M. tristis CW 482 (6) 1 0 5 1 0 5 3 2 1 M. tristis CW 485 (5) 0 1 4 1 0 4 4 0 1 M. tristis CW 488 (4) 0 0 4 0 0 4 2 2 0 M. tristis Total 9 6 77 6 4 82 65 22 5Family (*) Wild speciesinvolvedBrown leaf spot Anthracnose RustR RI S R RI S R RI SCW 444 (3) 2 1 0 3 0 0 0 3 0 M. flabellifoliaCW 450 (13) 0 3 10 2 5 6 13 0 0 M. flabellifoliaCW 460 (3) 0 1 2 1 2 0 3 0 0 M. flabellifoliaCW 533 (3) 3 0 0 3 0 0 3 0 0 M. flabellifoliaCW 445 (8) 7 1 0 5 3 0 3 4 1 M. tristis CW 441 (5) 3 1 1 3 2 0 4 1 0 M. tristis CW 453 (8) 0 0 8 1 3 4 8 0 0 M. tristis CW 482 (3) 0 3 0 0 1 2 0 1 2 M. tristis CW 484 (3) 0 3 0 3 0 0 2 1 0 M. tristis CW 488 (3) 0 3 0 0 3 0 3 0 0 M. tristis Total 15 16 21 21 19 12 39 10 3Wild speciesinvolvedFamily (*) Brown leaf spot Anthracnose RustSão Miguel das MatasIn summary,  genotypes with high levels of resistance to diseaseswere identified in all the places evaluated. Currently, replications ofthe promising hybrids are planted in these places aiming to performa more accurate evaluations and data analyses of disease resistanceand agronomic traits. In addition, characterization for  resistance toother diseases, such as bacterial blight, root rot and cassava mosaicveins virus will be performed in greenhouse conditions.Fig. 1. Symptoms disease affecting inter-specific cassava hybrids.  A-C: Anthracnose. D: Brownleaf spot. E: White leaf spot. F: Diffuse leaf spot. G-I: Rust.FDA B CG IHEMinistry ofAgriculture, Livestockand Food Supply

Evaluation of cassava interspecific hybrids for disease resistance

Rodríguez, M.A.D.

https://cgspace.cgiar.org/bitstream/10568/58095/1/Poster_Dita-Hybrids.pdf

Evaluation of cassava interspecific hybrids for disease resistance

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