Abstract

An experiment was carried out to study the covariance and co-heritability against prevalence of major diseases in 30 fine rice cultivars. The results revealed varying degrees of resistance against the major diseases. The cultivar, Ranjit was the top most yielder with 5.037 t/ha. Among the three major diseases, yield versus brown spot revealed the highest co-heritability (3.350) and yield versus disease index also showed the highest value (0.889). Except lodging percentage high heritability was measured for other selected characters. The growing condition was favorable for the incidence of brown spot that was predicted by the maximum environmental covariance (1.550) between yield versus brown spot. The yield potentials of Paijum, Kalozira and Begunbichi did not significantly differ from the highest yield of Ranjit and among them only Kalozira scored zero disease index. Cultivars, such as Zirashail, Nazirshail, Kaloshoru, Sadakatari, Binnipakri, Lalfota, Suman sorna, Moulata, Zaithakatari, Chinigura, Rajshahi sorna, Uknimodhu and Katari were in general poor yielder as compared to other cultivars but interestingly observed that the cultivars Nazirshail, Sadakatari and Sumon sorna scored zero disease indices against the three major diseases. Therefore, simultaneous consideration on yield and disease incidence in every cultivar was paid due attention during the investigation.

Key words: Covariance, co-heritability, disease incidence, fine rice.