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Accueil du site → Doctorat → Inde → 1990- 1999 → Studies on the mechanisms of resistance in pearl millet genotypes to downy mildew disease

Andhra Pradesh Agricultural University (1996)

Studies on the mechanisms of resistance in pearl millet genotypes to downy mildew disease

Chalam, V C

Titre : Studies on the mechanisms of resistance in pearl millet genotypes to downy mildew disease.

Auteur : Chalam, V C

Etablissement de soutenance : Andhra Pradesh Agricultural University.

Grade : PhD thesis (1996)

Studies on histopathological, anatomical, and biochemical differences between reslstant and susceptible pearl millet genotypes in relation to downy mildew disease were undertaken at the ICRISAT Ada center, Hyderabad. Indlrect sporangial germination by producing zoospores was observed. Loaspwe germ tubs penetrated the leaves directly through the epidermal cells, with or without appressarla and very rarely through stomata. The pathogen colonized the led tissue inter-and lntracellularly. Germindion ot sporangia and zoospores, and penetration was significantiy hlgher in susceptibie genotypes than the resistant ones. Sporangial and zoospore germination. and penetration decreased with the increase in leal age. me sporangial and zoospore germination and penetration were highest at 20’C and decreased with the further Increase M decrease in temperature. In redstant genotypes, 0-20 per cent led samples were colonized by S. gmminicola, where or In susceptible ones, colonization was 100 per cent. Colonization was extremely restricted in resistant genotypes. With few exceptions, cuticle thickness was signlccmtly more in resistant genotypes than the susceptible ones. The wax content was dgnilicantiy more in the three resistant genotypes (IP 18293, IP 18294, and IP 18296, than the susceptible ones with the exception of IP 18292 (resistant), in which wax content was less than the other resistant and Susceptible genotypes. A linear Increase in the cuticle thickness and wax content with the increase in Ibal age was obrervod. SignHicont diierences in number of stomata were not observed between the susceptible (HB 3 and 7042 S) and reslstant (IP 18294 and IP 18296) genotypes on both the sudaces. Similar obS8 lfi0nS were also made between reslstant genotype IP 18292 and susceptible genotype HB 3 on the upper surface. Total phenols were significanliy more in relstant genotypes than the susceptible ones, both In Inoculaiedand non-inoculated leaves. There was an increase in total phenols In both suscepfible and retltlant genotypes after inoculation. in case d redstant genotypes, IP 18292 and IP 18293, a didinct band was idenfflled close to the wlvent lront which Is abrent in SUKeptible ones, HB 3 & 7042 S. Total phenols and total soluble sugars mS) incread wHh the incr.oring ape of the seedlings. Total soluble suean did not diner slgnricantly between inocu aiedkd non-inoculated-leaves In redstantgenotypes. while in susceptible genotypes, the TSS were more in inoculated leaves.

Présentation ICRISAT

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