Rosamma, C AAmbili Nair, SKAU2020-11-032020-11-032000171735https://krishikosh.egranth.ac.in/handle/1/5810154251PGThe present investigation 'Genetic and physiological analysis of ratooning in rice (Oryza sativa L.)' was conducted at the Agricultural Research Station, Mannuthy during 1999-2000 to study the main crop as well as ratoon crop behaviour of different rice genotypes. The study was carried out to determine genetic variability among the different genotypes used. The study was also aimed at identifying morphological and physiological characters for a genotype of rice with high productivity when main and ratoon crop yields are combined together, through correlation and character association studies. Suitable selection indices were also formulated for identifying superior genotypes. Among the 50 genotypes evaluated in the main crop 24 showed regrowing ability. Of these five varieties viz. CO 43, IR 20, White Ponni, Ponmani and Mangala Mahsuri recorded better ratoon performance. The ratoon crop characters were less pronounced compared to the main crop characters except chlorophyll contents. But the above mentioned genotypes 'exhibited a higher intensity of character expression in both crops compared to the remaining genotypes. The estimates of GCV, heritability and genetic gain were high in the caseofratoon crop for most of the characters studied. Present study revealed that higher total yield can be achieved with a main crop having long duration and increased number of unproductive tillers plant". Ratoon yield can be improved by a better performing main crop with characters such as long duration, more number of grains panicle", more number of unproductive tillers plant" and reduced grain production day". Ratooning ability was considered as an index of the ratoon performance but in the present study ratooning ability recorded a negative direct effect on yield, indicating that this cannot be used as a true index to assess the ratoon performance. The various genetic and physiological analysis thus revealed that the varieties viz. IR 20, Mangala Mahsuri, White Ponni and Ponmani can be recommended as genotypes suitable for ratooning in Kerala. By using these about one third of the main crop yield can be achieved without increasing the land area. Total yield recorded 1;>y these genotypes were also significantly high.EnglishThesis