A Database for Triticeae and Avena
International Maize and Wheat Improvement Center - CIMMYT
Lisboa 27, Colonia Juárez, Apdo. Postal 6-641, 06600,
México, D.F., México.
Guillermo Fuentes-Dávila and Karim Ammar.
Introduction. Karnal bunt occurs naturally on bread
wheat (Mitra 1931), durum wheat, and triticale (X Triticosecale;
Agarwal et al. 1977). Affected kernels are usually partially infected
and completely infected ones are rare (Mitra 1935; Bedi et al.
1949; Chona et al. 1961). Since the early 1980s, it has been reported
about the resistance and immunity shown by triticale cultivars
and experimental advanced lines under artificial inoculations
(Meeta et al. 1980; Fuentes-Davila et al. 1992); therefore, advanced
lines were selected primarily for their resistance to a new race
of yellow rust that appeared in Central Mexico and to which most
CIMMYT triticales are susceptible (Hede et al. 2002). Sources
of resistance to this race also include progenies from crosses
with either bread or durum wheat. Continued evaluation for new
developed advanced lines and cultivars is important as a measure
to avoid possible economic problems to farmers, that could result
from the release of a susceptible cultivar.
Materials and Methods. Twenty elite triticale advanced
genotypes were evaluated for Karnal bunt resistance during the
crop cycle 2003-04. Planting dates were 20 November and 5 December,
2003, using approximately 10 g of seed for a bed with two rows
1-m long. A mist-irrigation system was used 3-5 times/day for
15 min each time to provide a humid environment in the experimental
area. Inoculation was by injection during the boot stage applying
1 ml of an allantoid sporidial suspension (10,000/ml) to ten heads/genotype.
Harvest was manual, and evaluating and counting of healthy and
infected kernels was by visual inspection. Tested genotypes included
the long-term yield check Pollmer TCL 2003, recently released
as feed-grain cultivar in the state of Sonora, and two new candidates
for commercial release in the same state. These three genotypes
are susceptible to yellow rust in central Mexico. The remaining
17 genotypes are new advanced lines selected for their resistance
to yellow rust in the Central Mexican Highlands and, internationally,
represent the genotypic variability available in the current feed
and forage triticale germ plasm of the CIMMYT program.
Results and Discussion. The range of infection for the
first planting date was 0-9.47, with a mean of 1.13. Ten lines
did not have any infected kernels (Figure 1). The range of infection for the
second planting date was 0-0.92, with a mean of 0.11. Sixteen
lines did not have any infected kernels. The difference between
the mean percent infection of the first and second planting dates
and the mean of the three highest levels of infection of the susceptible
check WL711 (65.98 %) was 64.9 and 65.87 %, respectively (Figure 2). Only the
line Dahbi_6/3/Ardi_1/Topo 1419//Erizo_9/4/Copi_1-1, CTSS99B00002S-0M-1Y-1M-1Y-0M,
fell within the 5.1-10 % infection category with 9.47 % on the
first date. Lines with less than 5 % infection are considered
resistant (Fuentes-Dávila and Rajaram 1994). Nine lines
did not have any infected kernels in either evaluation (Table
1). These results indicate that the high level of resistance to
Karnal bunt in triticale has been maintained in the new elite
germ plasm coming out of the CIMMYT program. Collaborative efforts
between INIFAP and CIMMYT to ensure adequate levels of Karnal
bunt resistance in new promising material is being continued in
order to provide a sound, safe, and commercially viable feed grain
option for the growers in the state of Sonora.
Table 1. Triticale genotypes that did not
show any infected kernels after artificial field inoculation with
Karnal bunt (Tilletia indica) on two planting dates
during the 2003-04 crop cycle in the Yaqui Valley, Sonora, Mexico.