Adult plant resistance genes with potential for durability to Puccinia recondita in wheat

R.N. Sawhney, J.B. Sharma and D.N. Sharma

Genetics Division, Indian Agricultural Research Institute, New Delhi- 110012, India


Adult plant resistance (APR) is conferred by genes that are ineffective in seedlings but become operative during stages of adult plant growth. They are implicated in durability of resistance. This communication deals with diverse APR genes/sources and their potential to impart durability.

Among the described genes for adult plant resistance, Lr34 has already been established to confer durable resistance (Sawhney, 1992; Sawhney et al. 1995a). In an expanded series of resistance genes, Lr35 deriving resistance from RL5347-Triticum speltoidesITriticum monococum (Sawhney et al. 1994) and Lr37 deriving resistance from Triticum ventricosum have been identified to be effective in adult plants. Lr35 resistance being operative only in adult plants and nonspecific is likely to be durable but its durability can only be confirmed after this gene is introduced in commercial cultivar and grown extensively (Sawhney et al. 1994).

Thatcher near-isogenic lines carrying Lr14b, Lr14ab, Lr30 showing seedling susceptibility to pathotypes exhibit resistance to the same pathotypes in adult plants (Sawhney et al. 1992). These lines also show APR against the highly virulent and newly evolved pathotype 77-5 and may confer durability.

In the variety Arjun seedling tests of SSD lines in F₇ of the cross Arjun x Kalyansona tested at higher temperature of 28C classified lines into (a) those that possess Lr13 and therefore show resistance, (b) those that lack this gene and were susceptible. F₂ and F₃ of the cross of the line lacking Lr13 with Agra Local (susceptible) gave segregates resistant at adult plant and therefore, established the presence of an APR gene which also possibly accounts for durability of resistance in Arjun.

Resistance responses on the Fed*4/Kavkaz and F₁ of the cross Federation x Kavkaz to pathotypes virulent on both Federation and Kavkaz was attributed to the possible complementation of adult plant resistance genes derived from Federation and Kavkaz (Sawhney et al. 1993). Resolution of this hypothesis was achieved by genetical data establishing that the leaf rust resistance in the stock is controlled by interaction of complementary adult plant genes. Additional interaction resistance to leaf rust in the class of 1BU1RS (wheat-rye translocation) wheats is likely to achieve durability for resistance to all the three rusts combined with high yields and environmental stability (Sawhney 1995).

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