Submitted to: Plant Disease
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/9/2004
Publication Date: 4/1/2005
Citation: Sharma, K.D., Chen, W., Muehlbauer, F.J. 2005. Genetics of chickpea resistance to five races of fusarium wilt and a concise set of race differentials for fusarium oxysporum f. sp. ciceris. Plant Disease. 89(4):385-390. Interpretive Summary: Fusarium wilt of chickpea caused by Fusarium oxysporum f. sp. ciceris is an important disease in many chickpea production regions. There are at least eight different races of the pathogen. Resistance to the races of Fusarium wilt is generally conditioned by major resistance genes. The genetics of resistance to race 5 in chickpea line WR-315 is not known, and the genetics of resistance to race 2 is controversial. This study using 100 F7 recombinant inbred lines derived from a cross between WR-315 and C-104 showed that resistance to race 5 in WR-315 is conditioned by one gene. It also showed that resistance to race 2 in WR-315 is conditioned by a single recessive gene. Knowing the number of genes involved in resistance is important in devising strategies to move the resistance genes to elite breeding lines and cultivars. We also observed a phenomenon termed slow wilting which is different from previously reported late wilting in three aspects: latent period, disease progress rate and final disease incidence. Identification of races is usually through using chickpea differentials. Previously reported differentials are imprecise in separating some races, particularly in separating between races 2 and 3. We identified a recombinant inbred line that can be used for unambiguously separation between races 2 and 3. After evaluating previously used differentials, we developed a concise differential set of ten chickpea lines that will offer important improvement over previous differential sets and provides more precise and unambiguous identification of the races.
Technical Abstract: Genetics of resistance in chickpea accession WR-315 to Fusarium wilt was investigated and a concise set of differentials was developed to identify races of Fusarium oxysporum f. sp. ciceris (Foc). A population of 100 F7 recombinant inbred lines (RILs) from a cross of WR-315 (resistant) and C-104 (susceptible) was used to study genetics of resistance to races 1, 2, 3, 4, and 5 of Foc, and a population of 26 F2 plants from a cross between the same two parents to study inheritance of resistance to race 2. Segregations of the RILs for resistance to each of the five races suggest that single genes in WR-315 govern resistance to each of the five races. A 1:3 resistant to susceptible ratio in the F2 population indicated that resistance in WR-315 to race 2 was governed by a single recessive gene. A race-specific slow disease progress reaction was observed in chickpea line FLIP84-92C(3) to infection by race 2, a phenomenon termed as slow witling that is different from previously reported late wilting in latent period, disease progress rate and final disease rating. Twenty-nine germplasm lines (27 Cicer arietinum and two C. reticulatum) including previously used differentials were evaluated for their reactions to infection by the five races. Only eight of the 29 germplasm lines differentiated at least one of the five races based on either resistant or susceptible reactions, whereas the remaining germplasm lines were either susceptible or resistant to all five races or differentiated them by intermediate reactions. A concise set of ten chickpea lines comprising of six genotypes and four F7 RILs with vertical resistance was developed as differentials for race identification in Foc. These differential lines were characterized by early appearance of wilt symptoms, and clear and consistent disease phenotypes based on no wilt or 100% wilt incidence, which offers important improvements over previously available differential sets and provides more precise and unambiguous identification of the races.