Spikelet sterility, harvest index and yield of rice (Oryza sativa) cultivars as influenced by low temperature and transplanting dates in temperate Kashmir

A field experiment was carried out during kharif seasons of 2006 and 2007 at Research Station Wadura of Sher-E-Kashmir university of Agricultural Sciences and Technology-Kashmir to study influence of low temperature and transplanting dates on rice spikelet sterility, harvest index and yield of rice (Oryza sativa L.) cultivars. Low temperature during the reproductive phase of rice caused marked reduction in grain yield of rice. Negative effect (% increase from normal early sowing) of late sowing on spikelet sterility was greatest in CV ‘Shalimar rice 1’ (15.8–50.9% increase over early and normal sowing) followed by ‘Jhelum’ (19.2–46%). Under late sown conditions, there was reduction in harvest index of cultivars in the order of ‘Shalimar Rice 1’> ‘Jhelum’> ‘Chenab’> ‘China 1039’. Heat susceptibility index (S) among different rice cultivars ranged from 0.82% in ‘Chenab’ to 1.17% in ‘Shalimar rice 1’ while, stability ratio raised from 46.28% in ‘Shalimar rice 1’ to 62.13% in ‘Chenab’. Low temperature induced sterility losses can be reduced by planting early.