SOYBEAN BREEDING IN BRAZILRust Resistance

José Francisco Ferraz de ToledoEmbrapa Soybean

MAIN CHALENGES

Large country - long distances Ever decreasing governmental fundsIncreased competition - private companies Private sector partnershipsKeep market shareNematode resistanceRust resistance / tolerance

EMBRAPA’s Institutional Arrangements for Soybean Breeding

SOUTHERN BRAZIL - 1Partnership – Embrapa and

Meridional Foundation

North

Northeast

Central

Southeast

South

CENTRAL BRAZILPartnership – Embrapa,

Agenciarural and CTPA

NORTHEASTERNBRAZIL

Partnership – Embrapaand FAPCEN

SOUTHEASTERNBRAZIL

Partnership – Embrapa, Epamig and Triangle Foundation

BrazilianRegions

SOUTHERN BRAZIL - 2Partnership – Embrapa and Pro-Seeds

Foundation

PERIODArea

103 haAreaIndex

Production103 Ton

Prodctvkg/ha

21,528.5 2,033

2,324

2,600

28,679.3

49,141.6

100.0

116.5

178.5

ProdIndex

ProdctvIndex

100.0 100.0

114.3

127.9

133.2

228.3

1991- 1995 10,589.5

1996 - 2000 12,340.5

2001 - 2006 18,900.6

•Early and Medium maturity groups are sowed in over 90% of the Parana State soybeanarea

Soybean yield genetic gain in Brazil

Genetic gain (%) Parana* State Mato Grosso State Mean

Maturity group E M E M L All

1981- 85 1.8 1.3 - - - 1.55

1985 - 90 0.89 0.38 - - - 0.64

1995 - 2000 - - 1.4 1.7 1.5 1.55

Annual mean 1.35 0.84 1.4 1.8 1.5 1.38

Important aspects in a breeding program for disease resistance

Economic impact (present and future)Incidence in time and space (or probability of occurrence)Pathogen variability: races and reproduction, dispersal and survival capacitySources of resistanceInheritance of resistanceEvaluation and selection methods

Soybean breeding for rust resistance

Rust is economic important and aggressive disease

Availability of resistance sources:o Identification of new resistant genotypes

o Major genes - identification of new majorresistance genes

o Minor genes

Major genes: inheritance, allele testing, molecular markers, backcrosses, winter season, etc. The idea is to incorporate ASAP these genes into the adapted Brazilian germplasm

Minor genes: quantitative trait with a relatively high genetic complexity. In this case, the program develops hundreds of segregating populations every year and grow the populations under disease pressure using natural selection

Major and minor genes together, trying to obtain desirable genotypes

Strategies to develop soybean cultivarsresistant / tolerant to rust

There are major genes already identified different from Rpp1 to Rpp4Those genes are being transferred into the Brazilian genetic germplasm through single crosses and backcrossesMolecular markers are being developed and may help stacking resistance genes

Soybean rust – major genes

Asian rust resistance – Major genes

Rpp1 - PI 200492, Tainung 3, Tainung 4, L85-2378Rpp2 - PI 230970, L86-1752, PI 197182, PI 230971,

PI 417125Rpp3 - PI 462312Rpp4 - PI 459025, L87-0482, Rpp5,6,… - Abura, PI 200487, Shiranui, PI 416819,

PI 417503, PI 416810, PI 417115, PI 417421,PI 423966, GC84058-21- 4

Major gene resistance

TAN RB

There are several different possibilities to consider:

Minor genes per se conferring resistance / tolerance Genes delaying disease developmentMinor genes with complementary effects to major genes, sometimes called background effect

Soybean rust – minor genes

Narrow sense heritabilities of rust severity investigated on F3 family means from crosses between genotypes carrying minor genes

hr2 = 0.42 to 0.74, therefore, moderate to high

These heritability values suggest selection is likely to result in genetic progress

First results from breeding forquantitative resistance

Early soybean genotypes evaluation and selection for Asian rust resistance does not ensure resistant adult plantsQuantitative genes expressing additive gene action for resistance to Asian rust are dispersed among soybean cultivarsSelection for Asian rust resistance based on F3 or later family means is likely to result in satisfactory genetic progress

First results from breeding forquantitative resistance

ns and ** indicate non-significance and significance at the 1% level of probability, respectively.

18.7015.111.45CV%

3.4213.888.01Mean

0.41ns4.40ns0.013ns108Exp. Error

0.47ns8.24**0.012ns34G x S

0.58ns5.76ns0.005ns2Plant stage (S)

2.32**14.03**0.012ns17Genotype (G)

SevLPIPdfSource ofVariation

Table 1. Mean squares from an analysis of variance for infectionincubation period (IP), latent period (LP) and severity (Sev) in genotypes inoculated with Phakopsora pachyrhizi in three sowing dates.

a52.67ab4.44a8.00BRS 133

c31.67abc3.56a8.00PI 562312

b42.67abc3.50a8.00BRS 231

b43.00bcd3.11a8.00PI 200492

--cd3.00a8.00BRS 232

d23.67cd2.94a8.00BRS 258

d18.67cd2.94a8.00PI 459025

d18.67d2.39a8.00PI 230970

Spore germinationSeverityIPGenotype

Means of infection period, severity and spore germination (%)of Phakopsora pachyrhizi.

c12,33ab12,67c10,33a14,00BRS 255RR

bc12,89ab12,33bc12,33a14,00BRS 231

bc12,89ab14,00bc12,00a12,67PI 200492

bc13,11ab14,33bc11,00a14,00BRS 154

bc13,17ab14,50bc14,00a11,00BRS 258

bc13,33ab12,00bc14,00a14,00BRS 133

bc13,44ab14,00bc14,00a12,33BRS 184

abc14,00ab14,00bc14,00a14,00BRS 214

abc14,11ab14,33bc14,00a14,00BRS 245RR

abc14,67ab12,67bc14,00a17,33EMBRAPA 48

abc14,78ab14,00abc16,33a14,00BRS 137

abc14,89ab14,33abc16,33a14,00BRS 232ab16,61a18,00ab17,50a14,33PI 459025a16,67ab14,00a22,00a14,00PI 230970

MeanInocul at V3Inocul at V5Inocul at R1 Genotype

TABLE – Latent period means of Phakopsora pachyrhiziinfection for inoculation at three plant stages.

Cross: Embrapa 48 x BRS 154

2

12

9

5 5

6

2

1

0

2

4

6

8

10

12

14

0-5 5-10 10-15 15-20 20-25 25-30 30-35 35-40 40-45 45-50 50-55 55-60

Severity score interval (%)2004/05

Num

ber

of F

3fa

mili

es

BRS 231

BRS154

Embrapa 48

Rust severity progress 2005/06

1015202530354045505560657075

2nd Assessm 3rd Assessm 4th Assessm

BR01-18437

BRS 184

BRS 231

BRS 232

RB

TAN

Rust severity progress 2005/06

10

1622

2834

40

4652

5864

70

2nd Assessm 3rd Assessm 4th Assessm

BR01-18437PI 200487PI 230970PI 459025-AShiranui

RB

All new resistant sources are being studied in allele testing to identify new major loci (RB reaction)

Identification of new sources (both RB and TAN reaction) based on experimental and commercial field information from Embrapa´sPartners

Genetic inheritance studies

Soybean rust – ongoing activities

Resistant / tolerant population development

Keep large population (> 3,000 individuals)Late sowings (later than Nov 15)Inoculation and irrigationSusceptible borders of several maturity groupsAdapted populations: plant selection for progeny rows in breeding programNon-adapted populations: plant selection for further crossing

Strategies for cropping RB cultivars withone or more major genes for rust resistance

Strategy 1: no fungicide application = high risko IF resistance doesn’t break – OK with good yield potentialo IF disease establishes and resistance breaks – significant

losses

Strategy 2: one fungicide application = average risko IF resistance doesn’t break – OK with good yield potentialo IF resistance breaks – some loss

Strategy 3: two fungicide applications = low risko IF resistance doesn’t break – OK with good yield potentialo IF resistance breaks – small losso Gain? Stability in areas with inefficient control

PI 200487(Kinoshita)

Border rows

MTBR 95 08675 BRS Gralha

BRS Pirarara BRS Tiana

Rust resistance experiment – hill plots

Rust resistance experiment – hill plots

Thanks !

Equator

Tropic of Capricorn