ARS | Publication request: INHERITANCE OF CHILLING INJURY: A MATERNALLY INHERITED TRAIT IN CUCUMBER

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 18, 2003
Publication Date: July 20, 2003
Citation: Chung, S., Staub, J.E., Fazio, G. 2003. Inheritance of chilling injury: a maternally inherited trait in cucumber. Journal of the American Society for Horticultural Science.

Interpretive Summary: Chilling injury is defined as damage causing physiological (i.e., wilting) and biochemical [i.e., decrease in chlorophyll (the green color in leaves) with exposure to light] changes. Such changes are induced by a temperature above the freezing point, but below 40°F. Many economically important crops such as corn, cotton, cucumber, squash, and tomato are chilling-sensitive during their development and fruiting. Because vegetable crops can be damaged by chilling temperatures during fruit development (lowering yield and fruit quality), the genetic improvement of chilling tolerance is an important plant breeding objective in many crop species. Cucumber plants are particularly sensitive to chilling temperatures and resistant/tolerant varieties have been identified. However, the inheritance (how traits such as chilling injury are transferred from parents to their offspring) of chilling injury has not been reported. Without this information plant breeders cannot work to develop improved high yield varieties with chilling resistance. Thus, a series of experiments were conducted to determine the genetic basis (inheritance) of chilling injury in cucumber. Data from parents (susceptible and resistant) and their progeny after mating indicated a complex inheritance not previously observed for other cucumber traits. The characterization and identification of chilling inheritance in cucumber will allow plant breeders to develop economically important chilling resistant varieties. Our experimental data will allow the plant breeder to become more efficient and effective in plant improvement, thus making the U.S. grower more competitive, and delivering a lower priced product to the consumer.

Technical Abstract: Chilling temperatures (=12°C) can cause substantial economic damage to cucumber (Cucumis sativus L.) plants. Numerous previous studies have suggested chilling tolerance trait is controlled by nuclear gene(s). To investigate inheritance of chilling injury in cucumber, a study was designed in which cucumber lines [susceptible GY-14 (P1), tolerant 'Chipper' (P2), and tolerant 'Little John' (P3)], and their exact reciprocal F1 and F2 cross-progeny were evaluated to determine the inheritance of chilling injury at the first true-leaf stage when challenged at 4°C for 5.5 hr. The mean chilling ratings [1(trace)-9(dead)] of progeny comparisons were: F1(P1xP2) = 6.2 vs. F1(P2xP1) = 1.2; F2(P1xP2) = 6.4 vs. F2(P2xP1) = 2.7; F1(P1xP3) = 5.4 vs. F1(P3xP1) = 1.7, and; F2(P1xP3) = 5.8 vs. F2(P3xP1) = 2.2. These data suggest that chilling tolerance trait is maternally inherited in cucumber. Parents, reciprocal F1, and F2 progeny were evaluated for variation using random amplified polymorphism DNA (RAPD). Although no maternally inherited RAPD markers were detected, polymorphic and paternally inherited RAPD bands AD21249, AV8916, and AV8969 amplified by AD2 and AV8 primers were cloned and sequenced. A "BLAST" search employing these sequences suggested that their origin is likely cucumber mitochondrial DNA. These results indicate that the mitochondria genome is not associated with the chilling tolerant trait because this genome is paternally inherited in progeny derived from this reciprocal mating. Therefore, the results of maternally inherited chilling tolerant trait and paternally transmitted mitochondria genome support that the chilling tolerant trait as identified is likely associated with the chloroplast genome which is itself maternally transmitted in cucumber.