Studies on fungal leaf blight of ridge gourd [Luffa acutangula (L.) Roxb.] in Kashmir valley

An extensive survey conducted during 2004 and 2005 revealed that Didymella blight was prevalent in all ridge gourd (Luffa acutangula) growing areas of Kashmir valley with varied levels of incidence and intensity. The incidence and intensity on leaves ranged from 22.0 to 64.0 and 7.7 to 34.8 per cent, respectively. The incidence on fruits was 6.8 to 18.8 per cent. The fungus inciting the disease was identified as Didymella bryoniae (Aureswarld) Rehm (Anamorph Phoma cucurbitacearum (Foutrey) Sacardo) on the basis of its morphological and pathological characteristics. Disease infection on leaves and fruits resulted in leaf blight and fruit rot, respectively. Disease initially appeared on lower leaves as small circular, light brown spots with chlorotic halo ranging in size from 0.5 to 1.0 mm. With the passage of time spots enlarged (up to 83 mm size) , developed concentric rings at the centre and turned dark brown with greyish white centre. The spots then coalesced, causing yellowing and blighting of the entire leaf. Symptoms on fruit appeared as dark green, irregularly circular water-soaked spots which enlarged rapidly and caused black rot. Black fructifications i.e, pycnidia and pseudothecia of the causal pathogen, were observed on infected tissue of both leaf and fruit which imparted black colour to the latter. The disease in the field appeared in June and reached its maximum by the end of September. Maximum apparent infection rate of 0.1858 and 0.1826 unit/day in the field were observed during fifth week of July in 2004 and during second week of July in 2005, respectively. Weather factors viz., temperature, RH and rainfall were found positively correlated with the disease development in terms of infection rate (unit/day) with 69 per cent contribution by rainfall alone. Single spored cultures from ascospore and pycnidiospore on potato dextrose agar (PDA) produced pycnidia after 10 to 12 days of incubation at 24±10C under 12/12 hour alternate cycles of light and darkness, however, pseudothecia were altogether absent. The fungus required incubation period of 4 days to cause infection in the inoculated host plants, whereas, on detached leaf and fruit it took 2 to 3 days. The fungus was found pathogenic to all the eight cucurbit plant species tested viz., Cucumis sativus (cucumber), Lagenaria siceraria (bottle gourd), Cucumis melo (muskmelon), Citrullus lanatus (watermelon), Mamordicha charantia (bitter gourd), Cucurbita pepo (squash), Luffa cylindrica (sponge gourd) and Cucurbita pepo (pumpkin) besides its natural host Luffa acutangula (ridge gourd) both under natural and artificial inoculation conditions. The best growth and fructification of the fungus was observed on potato dextrose agar and corn meal agar media with pH 7.0 when incubated at 24 ± 1 0C. Spore germination was also best at this temperature and pH level. The pathogen perpetuated in the form of spores on seeds and plant debris stored indoors under ambient laboratory conditions as these produced viable spores through out the observation period of twelve months. It also perpetuated as a dormant mycelium on plant debris left on the soil surface in open, however, pathogen was unable to survive on plant debris buried 7.5 cm deep in soil. Carbendazim and chlorothalonil from systemic and non-systemic fungitoxicants, respectively, as well as Allium sativum from botanicals tested under in vitro conditions exhibited maximum inhibition in mycelial growth and spore germination of the test fungus. The treatments found most promising under in vitro studies, when tested as seed treatment and foliar spray, treatment combination carbendazim seed treatment together with foliar sprays of carbendazim proved superior in controlling the disease and also increasing the fruit yield

“Studies on Corm Rot of Saffron (Crocus Sativus L.)”

Saffron (Crocus sativus L.) is an important cash crop. The incidence of corm rot ranged from 4.00-42.00 per cent and intensity from 0.8 - 17.46 per cent. Three species of Fusarium viz. F. solani, F. moniliforme and F. oxysporum along with nematodes were found to be invariably involved in causing corm rot. The occurrence of three pathogenic species of Fusarium varied with the stages of crop development F. solani at digging and harvesting stage, F. moniliforme and F. oxysporum in storage. Interaction of F. solani nematodes showed a highest incidence of 50.00 per cent and intensity of 14.66 per cent compared to check. Three management practices using non-chemical and non-hazardous organic amendments, bioagent and soil solarization reduced incidence of the disease with organic amendments showing corm rot incidence of 23.33 – 40.00 per cent compared to 50.00 per cent in check and saffron yield was enhanced from 10.00 – 75.00 per cent. Similarly bioagents also reduced the intensity of corm rot with Trichoderma viride giving maximum control and showing an intensity of 13.33 per cent compared to 27.33 per cent in check. Six weeks soil solarization reduced corm rot incidence 52.2 per cent during 2000 and 41.9 per cent during2001 season. All the approaches have significantly affected in reducing the corm rot and increasing the yield. However, an integrated approach of soil solarization after irrigation and addition of FYM/ poultry manure in the ratio 4:1 was best treatment