Transcript CIMMYTs
Yellow rust and Karnal bunt of wheat “CIMMYTs experience” Arun K Joshi Global Wheat Program, CIMMYT [email protected] Contributions from: Ravi P. Singh, Hans Braun, Pawan Singh, Jessica Rutkoski Global priorities for wheat diseases Biotic stress East South West M-East+ C-Asia+ S-Saharan L-Americ. Developed Asia Asia Asia N-Africa Caucasus Africa + Mexico countries Leaf rust Stem rust Yellow rust FHB Septoria Spot blotch Tan spot Nematodes Root diseases Smuts/bunts Wheat blast ++ +++ +++ +++ + + 0 ++ ++ + 0 ++ Powdery mildew +++ +++ ++ 0 0 ++ + ++ + + 0 + +++ +++ +++ + ++ 0 0 +++ ++ ++ 0 0 +++ +++ +++ 0 +++ 0 + ++ ++ ++ 0 0 +++ +++ +++ 0 ++ 0 +++ 0 + + 0 0 ++ +++ +++ 0 ++ + 0 + + + 0 0 +++ +++ + ++ ++ + ++ + + + + + ++ +++ +++ +++ +++ 0 ++ + + 0 0 ++ “Karnal bunt is not specified; too localized, but important for India” Current Concern Aggressive strains of yellow rust with Yr27+ virulence Rust neither sleeps nor respects international boundaries ● East Africa is a center for new emerging rust races (Yr9, Ug99 etc). Yr27 virulence has ● Mid 80’s to mid 90’s Yr9 virulent races caused significant crop losses all the way from East Africa to South Asia. 1991 1992/3 1993/4 1994/5 also been traced back to Africa 1995/6 Yr9 1991 1986 1986 International collaboration important Example Losses: Turkey (1995): USD$ 568 Million Iran (1992-94): USD$ 158 Million Aggressive yellow rust races adapted to higher temperature ● Initiation of infection earlier in the season at juvenile growth stages ● Faster multiplication & higher disease build up ● Disease progression even when temperatures are warmer ● New areas of adaptation ● Faster rate of evolution Need to develop varieties with ● Reduced effectiveness of resistance higher levels of resistance genes (including APR) We focus on a longterm solution “Non race-specific resistance” Use of a single major gene causes boom and bust cycle Photo: Indu Sharma, DWR, India We shuttle breeding populations With in Mexico (Cd. Obregon-Toluca/El Batan) & with Kenya Cd. Obregón 39 masl High yield (irrigated), Water-use efficiency, Heat tolerance, Leaf rust, stem rust (not Ug99) Toluca 2640 masl Yellow rust Septoria tritici Fusarium El Batán 2249 masl Leaf rust, Fusarium Tan spot ● Mexico-Kenya Shuttle breeding initiated in 2006 ● About 2000 F3/F4 populations undergo shuttled annually ● High yielding, resistant lines distributed worldwide since 2011 Njoro, Kenya 2185 masl Stem rust (Ug99 group) Yellow rust What is done to simplify breeding? Targeted Incorporation of 45 Minor, Additive Genes Through ‘Single-backcross, Selected-Bulk’ Approach Artificial epidemic is ensured Karnal Bunt Managing Karnal Bunt 1. 2. 3. 4. 5. Use of pathogen-free wheat seed Seed treatment Foliar sprays: Fungicides (mancozeb, carbendazim, fentin hydroxide, bitertanol and propiconazole (Tilt at 0.1%-Best) give effective control if applied at the heading stage. Cultural practices Host Resistance: Best strategy but still to be demonstrated in large scale. Breeding for Resistance to KB ● Resistance sources in bread wheat are known but important varieties are susceptible ● Durums are more resistant ● Resistance is complex; requires pyramiding 4-5 additive genes with small to intermediate ● Screening for resistance is cumbersome; 2-3 years of screening is necessary to confirm resistance CIMMYT derived Indian wheat variety ‘Super172’ (Munal) has shown nearzero KB infection in 5 years of testing in Mexico. However it is now showing moderate susceptibility to yellow rust in India Genomic selection phenotyping at BISA Thank you Picture: Posci.com