Climate change refers to long term conspicuous deviation from usual prevalent climate bringing variation in normal temperature, rainfall and atmospheric circulation with abnormal expression in extreme climate such as floods, droughts, extreme temperatures etc. can be termed as climate change (Ghadekar et al, 2001). India produces about 24 million tonnes of potato from 1.32 million hectares under the crop. India is the second largest producer of potato in the world. The Indo-Gangetic plains (IGP) is the main potato growing region accounting for almost 85% of the 1.8 Mha under the crop in India where it is grown as an irrigated crop during the winter season. The bulk of the produce comes from states of Uttar Pradesh (UP), West Bengal (WB), Punjab and Bihar contributing 40, 32, 6 and 6 per cent, respectively. Global studies projected a 10-40% loss in crop production in India by 2080-2100 due to climate change unless farmers adapt to climate change (IPCC, 2007). The potato crop duration in the Indo-Gangetic plains is projected to decrease due to climate change. Potato growth and development is affected at high temperatures. Potato is well known for its exact temperature and day length requirement for tuber formation as well as flowering, so it becomes the most vulnerable crop for climate change. The effect of climate change on potato production in India has previously been studied by Singh et al (2009). Potato productivity is expected to decline in all potato growing states of India. Potato crop growth is not possible below 2oC and above 30oC. Cardinal temperature for net photosynthesis of potato have been reported as minimum (0-7oC), optimum (16-25oC) and maximum (40oC). Potato requires cool night temperature to induce tuberization (Ewing, 1997). Potato is frost sensitive and severe damage may occur when temperature drops below 0oC (Hijmans et al 2003). Potato is well known for its exact temperature and day length requirement for tuber formation as well as flowering, so it becomes the most vulnerable crop for climate change. The effect of climate change on potato production in India has previously been studied by Singh et al., (2009). Potato productivity is expected to decline in all potato growing states of India Potato productivity is expected to decline in all potato growing states of India (Table 2). The influence of climate change on potato production and the disease, Potato Late Blight, was reviewed.
Climate change and potato productivity
Luck et al., (2010) expected 16% decline in tuber yield of potato by 2050 for West Bengal if any special strategies are not adapted. However, they suggested planting of potato crop at a new optimal date of mid November in order to minimize the yield losses up to 8%. Increase in
temperature favours the potato cultivation by prolonging the crop growing season in high altitudes and temperate regions of the world like Europe, Russia and in India, Himalayan and other mountain regions and frost prone states like Haryana and Punjab (Table 2) whereas, it disfavours the potato production by shortening the growing period in subtropical plains such as West Bengal and Bihar during winter season (Singh, 2010). Potato requires long days and low temperatures for its flowering. It makes possible the hybridization or heterosis breeding of potato in high altitudes of Himachal Pradesh. Due to increase in temperature the potato breeding area is shifting towards the further more high altitudes. Potato is very strict to its temperature requirement for tuber formation. Optimum tuber formation takes place at 200 C. An increase in
temperature of above 210 C cause sharp reduction in the potato tuber yield, at 300 C complete inhibition of tuber formation occurs (Sekhawat, 2001). In potato high harvesting index (HI) of 0.8 is recorded at 150 C night temperatures of and zero at 280 C in Northern Indian Punjab, Haryana, Uttar Pradesh, Bihar and Northern hills. A moderate HI of 0.4-0.6 is recorded at 200 C night temperatures in Central Indian states like Gujarat, Chattisgarh, some parts of Maharashtra and West Bengal indicating temperature stress limiting the partitioning of photosynthates to the tubers. A low HI of 0.2 is recorded at more than 200 C night temperatures in South India (Pandey et al., 2009; Singh, 2010). Potato tubers with high starch content are favored by the processing industry. At low temperatures starch is converted into the sugar, which causes browning due to charring of sugar while chips making there by reduces their preference by the processing industry. This ultimately results in increased post harvest losses more than the present level, which is figured as 40-50%. This is most common problem in areas where night temperatures fell below optimum during winter season (Singh, 2010). Fruit colour is having significant importance in assessing the marketable quality of tomato. The optimum temperature for development of lycopene pigment in tomato is 25-30o C. Degradation of lycopene starts at above 270 C and it is
completely destroyed at 400 C. Similarly high temperatures above 250 C affect pollination and fruit set in tomato (Kalloo et al., 2001). Abnormal pollen production, abnormal development of the female reproductive tissues, hormonal imbalances and lower levels of carbohydrates and lack of
pollination are responsible for the poor reproductive performance of tomatoes at high temperatures (Peet et al.,1997). Lurie et al., (1996) reported high temperature inhibits ripening by inhibiting the accumulation of ripening related m-RNAs, thereby inhibits continuous protein synthesis including ethylene production, lycopene accumulation and cell-wall dissolution. In pepper, exposure to high temperature at post-pollination stage inhibits fruit set (Erickson and Markhart 2002). High temperature affects red colour development in ripen chilli fruits and also causes flower drop, ovule abortion, poor fruit set and fruit drop in chilli (Arora et al., 1987). Flynn et al. (2002) found high percentage (90%) seed germination of chilli at 200 C and complete inhibition at 100 C indicating that fall in minimum temperatures affect seed germination in chilli.
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