Spot Blotch (wheat) - Breeding For Resistance

Breeding For Resistance

The wheat cultivars of South Asia have only low to moderate levels of resistance to spot blotch. However, genetic variation for resistance has been reported in a few wheat. The best sources of resistance, to date, were identified in the Brazilian and Zambian wheat lines. Recently, a few Chinese wheat genotypes from the Yangtze river valley were identified with acceptable levels of resistance to spot blotch. The following genotypes has been reported to have satifactory level of resistance, although complete resistance or immunity is lacking

1 SW 89-5193

2 SW 89-3060

3 SW 89-5422

4 Chirya 7

5 Ning 8319

6 NL 781

7 Croc 1/A. sq.// Borl

8 Chirya 3

9 G162

10 Chirya 1

11 Yangmai-6

12 NL 785

The field resistance governed by Chirya-3 and Milan / Sanghai 7 was found under monogenic control

Similarly resistant genotypes Acc. No. 8226, Mon/Ald, Suzhoe#8 from India are found to possess three genes for resistance.

A study was conducted to determine microsatellite markers associated with resistance in the F7 progeny from a cross between the spot blotch-susceptible Sonalika and resistant G162 wheat genotypes. 15 polymorphic markers showed association with two bulks, one each of progeny with low and with high spot blotch severity.

One of interesting phenomena associated with foliar blight in some of susceptible cultivar is tolerance (low yield loss even at very high level of disease severity). In addition, the resistance seems to be associated with late maturity (which is undesirable character as late maturing genotypes need to face more heat stress than early ones), complete understanding of physiological association may aid to complete understanding of the host-pathogen system.

Rosyara et al. reported that the AUDPC showed a significant negative correlation with the width of large vascular bundles, percentage of small vascular bundles with two girders and the number of large veins. Also the AUDPC was positively correlated with the distance between adjacent vascular bundles and leaf thickness. The chlrophyll or general health indicators, SPAD and AUSDC values were higher in spot blotch resistant and tolerant genotypes. The findings the study underlined the importance of mesophyll structure and chlorophyllcontent in spot blotch resistance in wheat. Also tolerant genotypes responded in the same way as artificial defoliation showing mechanisms of nutrient balance playing role. Similarly, canopy temperature depression was found associated with foliar blight resistance. Leaf tip necrosis was found to be associated with foliar blight resistance and is suggested as phenotypic marker. Different studies are done to estimate heritability and increase selection efficiency. Heritability estimates were low to high in terms of AUDPC .To increase efficiency of selection use of selection index has been suggested. The index includes days to heading (maturity related trait), thousand kernel weight, and area under foliar blight disease progress curve.

Read more about this topic:  Spot Blotch (wheat)

Famous quotes containing the words breeding and/or resistance:

    The Fashionable World is grown free and easie; our Manners sit more loose upon us: Nothing is so modish as an agreeable Negligence. In a word, Good Breeding shows it self most, where to an ordinary Eye it appears the least.
    Joseph Addison (1672–1719)

    It is not the first duty of the novelist to provide blueprints for insurrection, or uplifting tales of successful resistance for the benefit of the opposition. The naming of what is there is what is important.
    Ian McEwan (b. 1938)